results and discussion in research paper sample

Guide to Writing the Results and Discussion Sections of a Scientific Article

A quality research paper has both the qualities of in-depth research and good writing ( Bordage, 2001 ). In addition, a research paper must be clear, concise, and effective when presenting the information in an organized structure with a logical manner ( Sandercock, 2013 ).

In this article, we will take a closer look at the results and discussion section. Composing each of these carefully with sufficient data and well-constructed arguments can help improve your paper overall.

The results section of your research paper contains a description about the main findings of your research, whereas the discussion section interprets the results for readers and provides the significance of the findings. The discussion should not repeat the results.

Let’s dive in a little deeper about how to properly, and clearly organize each part.

How to Organize the Results Section

Since your results follow your methods, you’ll want to provide information about what you discovered from the methods you used, such as your research data. In other words, what were the outcomes of the methods you used?

You may also include information about the measurement of your data, variables, treatments, and statistical analyses.

To start, organize your research data based on how important those are in relation to your research questions. This section should focus on showing major results that support or reject your research hypothesis. Include your least important data as supplemental materials when submitting to the journal.

The next step is to prioritize your research data based on importance – focusing heavily on the information that directly relates to your research questions using the subheadings.

The organization of the subheadings for the results section usually mirrors the methods section. It should follow a logical and chronological order.

Subheading organization

Subheadings within your results section are primarily going to detail major findings within each important experiment. And the first paragraph of your results section should be dedicated to your main findings (findings that answer your overall research question and lead to your conclusion) (Hofmann, 2013).

In the book “Writing in the Biological Sciences,” author Angelika Hofmann recommends you structure your results subsection paragraphs as follows:

• Experimental purpose
• Interpretation

Each subheading may contain a combination of ( Bahadoran, 2019 ; Hofmann, 2013, pg. 62-63):

• Text: to explain about the research data
• Figures: to display the research data and to show trends or relationships, for examples using graphs or gel pictures.
• Tables: to represent a large data and exact value

Decide on the best way to present your data — in the form of text, figures or tables (Hofmann, 2013).

Data or Results?

Sometimes we get confused about how to differentiate between data and results . Data are information (facts or numbers) that you collected from your research ( Bahadoran, 2019 ).

Whereas, results are the texts presenting the meaning of your research data ( Bahadoran, 2019 ).

One mistake that some authors often make is to use text to direct the reader to find a specific table or figure without further explanation. This can confuse readers when they interpret data completely different from what the authors had in mind. So, you should briefly explain your data to make your information clear for the readers.

Common Elements in Figures and Tables

Figures and tables present information about your research data visually. The use of these visual elements is necessary so readers can summarize, compare, and interpret large data at a glance. You can use graphs or figures to compare groups or patterns. Whereas, tables are ideal to present large quantities of data and exact values.

Several components are needed to create your figures and tables. These elements are important to sort your data based on groups (or treatments). It will be easier for the readers to see the similarities and differences among the groups.

When presenting your research data in the form of figures and tables, organize your data based on the steps of the research leading you into a conclusion.

Common elements of the figures (Bahadoran, 2019):

• Figure number
• Figure title
• Figure legend (for example a brief title, experimental/statistical information, or definition of symbols).

Tables in the result section may contain several elements (Bahadoran, 2019):

• Table number
• Table title
• Row headings (for example groups)
• Column headings
• Row subheadings (for example categories or groups)
• Column subheadings (for example categories or variables)
• Footnotes (for example statistical analyses)

Tips to Write the Results Section

• Direct the reader to the research data and explain the meaning of the data.
• Avoid using a repetitive sentence structure to explain a new set of data.
• Write and highlight important findings in your results.
• Use the same order as the subheadings of the methods section.
• Match the results with the research questions from the introduction. Your results should answer your research questions.
• Be sure to mention the figures and tables in the body of your text.
• Make sure there is no mismatch between the table number or the figure number in text and in figure/tables.
• Only present data that support the significance of your study. You can provide additional data in tables and figures as supplementary material.

How to Organize the Discussion Section

It’s not enough to use figures and tables in your results section to convince your readers about the importance of your findings. You need to support your results section by providing more explanation in the discussion section about what you found.

In the discussion section, based on your findings, you defend the answers to your research questions and create arguments to support your conclusions.

Below is a list of questions to guide you when organizing the structure of your discussion section ( Viera et al ., 2018 ):

• What experiments did you conduct and what were the results?
• What do the results mean?
• What were the important results from your study?
• How did the results answer your research questions?
• Did your results support your hypothesis or reject your hypothesis?
• What are the variables or factors that might affect your results?
• What were the strengths and limitations of your study?
• What other published works support your findings?
• What other published works contradict your findings?
• What possible factors might cause your findings different from other findings?
• What is the significance of your research?
• What are new research questions to explore based on your findings?

Organizing the Discussion Section

The structure of the discussion section may be different from one paper to another, but it commonly has a beginning, middle-, and end- to the section.

One way to organize the structure of the discussion section is by dividing it into three parts (Ghasemi, 2019):

• The beginning: The first sentence of the first paragraph should state the importance and the new findings of your research. The first paragraph may also include answers to your research questions mentioned in your introduction section.
• The middle: The middle should contain the interpretations of the results to defend your answers, the strength of the study, the limitations of the study, and an update literature review that validates your findings.
• The end: The end concludes the study and the significance of your research.

Another possible way to organize the discussion section was proposed by Michael Docherty in British Medical Journal: is by using this structure ( Docherty, 1999 ):

• Discussion of important findings
• Comparison of your results with other published works
• Include the strengths and limitations of the study
• Conclusion and possible implications of your study, including the significance of your study – address why and how is it meaningful
• Future research questions based on your findings

Finally, a last option is structuring your discussion this way (Hofmann, 2013, pg. 104):

• First Paragraph: Provide an interpretation based on your key findings. Then support your interpretation with evidence.
• Secondary results
• Limitations
• Unexpected findings
• Comparisons to previous publications
• Last Paragraph: The last paragraph should provide a summarization (conclusion) along with detailing the significance, implications and potential next steps.

Remember, at the heart of the discussion section is presenting an interpretation of your major findings.

Tips to Write the Discussion Section

• Highlight the significance of your findings
• Mention how the study will fill a gap in knowledge.
• Indicate the implication of your research.
• Avoid generalizing, misinterpreting your results, drawing a conclusion with no supportive findings from your results.

Aggarwal, R., & Sahni, P. (2018). The Results Section. In Reporting and Publishing Research in the Biomedical Sciences (pp. 21-38): Springer.

Bahadoran, Z., Mirmiran, P., Zadeh-Vakili, A., Hosseinpanah, F., & Ghasemi, A. (2019). The principles of biomedical scientific writing: Results. International journal of endocrinology and metabolism, 17(2).

Bordage, G. (2001). Reasons reviewers reject and accept manuscripts: the strengths and weaknesses in medical education reports. Academic medicine, 76(9), 889-896.

Cals, J. W., & Kotz, D. (2013). Effective writing and publishing scientific papers, part VI: discussion. Journal of clinical epidemiology, 66(10), 1064.

Docherty, M., & Smith, R. (1999). The case for structuring the discussion of scientific papers: Much the same as that for structuring abstracts. In: British Medical Journal Publishing Group.

Faber, J. (2017). Writing scientific manuscripts: most common mistakes. Dental press journal of orthodontics, 22(5), 113-117.

Fletcher, R. H., & Fletcher, S. W. (2018). The discussion section. In Reporting and Publishing Research in the Biomedical Sciences (pp. 39-48): Springer.

Ghasemi, A., Bahadoran, Z., Mirmiran, P., Hosseinpanah, F., Shiva, N., & Zadeh-Vakili, A. (2019). The Principles of Biomedical Scientific Writing: Discussion. International journal of endocrinology and metabolism, 17(3).

Hofmann, A. H. (2013). Writing in the biological sciences: a comprehensive resource for scientific communication . New York: Oxford University Press.

Kotz, D., & Cals, J. W. (2013). Effective writing and publishing scientific papers, part V: results. Journal of clinical epidemiology, 66(9), 945.

Mack, C. (2014). How to Write a Good Scientific Paper: Structure and Organization. Journal of Micro/ Nanolithography, MEMS, and MOEMS, 13. doi:10.1117/1.JMM.13.4.040101

Moore, A. (2016). What's in a Discussion section? Exploiting 2‐dimensionality in the online world…. Bioessays, 38(12), 1185-1185.

Peat, J., Elliott, E., Baur, L., & Keena, V. (2013). Scientific writing: easy when you know how: John Wiley & Sons.

Sandercock, P. M. L. (2012). How to write and publish a scientific article. Canadian Society of Forensic Science Journal, 45(1), 1-5.

Teo, E. K. (2016). Effective Medical Writing: The Write Way to Get Published. Singapore Medical Journal, 57(9), 523-523. doi:10.11622/smedj.2016156

Van Way III, C. W. (2007). Writing a scientific paper. Nutrition in Clinical Practice, 22(6), 636-640.

Vieira, R. F., Lima, R. C. d., & Mizubuti, E. S. G. (2019). How to write the discussion section of a scientific article. Acta Scientiarum. Agronomy, 41.

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Home » Research Results Section – Writing Guide and Examples

Research Results Section – Writing Guide and Examples

Table of Contents

Research Results

Research results refer to the findings and conclusions derived from a systematic investigation or study conducted to answer a specific question or hypothesis. These results are typically presented in a written report or paper and can include various forms of data such as numerical data, qualitative data, statistics, charts, graphs, and visual aids.

Results Section in Research

The results section of the research paper presents the findings of the study. It is the part of the paper where the researcher reports the data collected during the study and analyzes it to draw conclusions.

In the results section, the researcher should describe the data that was collected, the statistical analysis performed, and the findings of the study. It is important to be objective and not interpret the data in this section. Instead, the researcher should report the data as accurately and objectively as possible.

Structure of Research Results Section

The structure of the research results section can vary depending on the type of research conducted, but in general, it should contain the following components:

• Introduction: The introduction should provide an overview of the study, its aims, and its research questions. It should also briefly explain the methodology used to conduct the study.
• Data presentation : This section presents the data collected during the study. It may include tables, graphs, or other visual aids to help readers better understand the data. The data presented should be organized in a logical and coherent way, with headings and subheadings used to help guide the reader.
• Data analysis: In this section, the data presented in the previous section are analyzed and interpreted. The statistical tests used to analyze the data should be clearly explained, and the results of the tests should be presented in a way that is easy to understand.
• Discussion of results : This section should provide an interpretation of the results of the study, including a discussion of any unexpected findings. The discussion should also address the study’s research questions and explain how the results contribute to the field of study.
• Limitations: This section should acknowledge any limitations of the study, such as sample size, data collection methods, or other factors that may have influenced the results.
• Conclusions: The conclusions should summarize the main findings of the study and provide a final interpretation of the results. The conclusions should also address the study’s research questions and explain how the results contribute to the field of study.
• Recommendations : This section may provide recommendations for future research based on the study’s findings. It may also suggest practical applications for the study’s results in real-world settings.

Outline of Research Results Section

The following is an outline of the key components typically included in the Results section:

I. Introduction

• A brief overview of the research objectives and hypotheses
• A statement of the research question

II. Descriptive statistics

• Summary statistics (e.g., mean, standard deviation) for each variable analyzed
• Frequencies and percentages for categorical variables

III. Inferential statistics

• Results of statistical analyses, including tests of hypotheses
• Tables or figures to display statistical results

IV. Effect sizes and confidence intervals

• Effect sizes (e.g., Cohen’s d, odds ratio) to quantify the strength of the relationship between variables
• Confidence intervals to estimate the range of plausible values for the effect size

V. Subgroup analyses

• Results of analyses that examined differences between subgroups (e.g., by gender, age, treatment group)

VI. Limitations and assumptions

• Discussion of any limitations of the study and potential sources of bias
• Assumptions made in the statistical analyses

VII. Conclusions

• A summary of the key findings and their implications
• A statement of whether the hypotheses were supported or not
• Suggestions for future research

Example of Research Results Section

An Example of a Research Results Section could be:

• This study sought to examine the relationship between sleep quality and academic performance in college students.
• Hypothesis : College students who report better sleep quality will have higher GPAs than those who report poor sleep quality.
• Methodology : Participants completed a survey about their sleep habits and academic performance.

II. Participants

• Participants were college students (N=200) from a mid-sized public university in the United States.
• The sample was evenly split by gender (50% female, 50% male) and predominantly white (85%).
• Participants were recruited through flyers and online advertisements.

III. Results

• Participants who reported better sleep quality had significantly higher GPAs (M=3.5, SD=0.5) than those who reported poor sleep quality (M=2.9, SD=0.6).
• See Table 1 for a summary of the results.
• Participants who reported consistent sleep schedules had higher GPAs than those with irregular sleep schedules.

IV. Discussion

• The results support the hypothesis that better sleep quality is associated with higher academic performance in college students.
• These findings have implications for college students, as prioritizing sleep could lead to better academic outcomes.
• Limitations of the study include self-reported data and the lack of control for other variables that could impact academic performance.

V. Conclusion

• College students who prioritize sleep may see a positive impact on their academic performance.
• These findings highlight the importance of sleep in academic success.
• Future research could explore interventions to improve sleep quality in college students.

Example of Research Results in Research Paper :

Our study aimed to compare the performance of three different machine learning algorithms (Random Forest, Support Vector Machine, and Neural Network) in predicting customer churn in a telecommunications company. We collected a dataset of 10,000 customer records, with 20 predictor variables and a binary churn outcome variable.

Our analysis revealed that all three algorithms performed well in predicting customer churn, with an overall accuracy of 85%. However, the Random Forest algorithm showed the highest accuracy (88%), followed by the Support Vector Machine (86%) and the Neural Network (84%).

Furthermore, we found that the most important predictor variables for customer churn were monthly charges, contract type, and tenure. Random Forest identified monthly charges as the most important variable, while Support Vector Machine and Neural Network identified contract type as the most important.

Overall, our results suggest that machine learning algorithms can be effective in predicting customer churn in a telecommunications company, and that Random Forest is the most accurate algorithm for this task.

Example 3 :

Title : The Impact of Social Media on Body Image and Self-Esteem

Abstract : This study aimed to investigate the relationship between social media use, body image, and self-esteem among young adults. A total of 200 participants were recruited from a university and completed self-report measures of social media use, body image satisfaction, and self-esteem.

Results: The results showed that social media use was significantly associated with body image dissatisfaction and lower self-esteem. Specifically, participants who reported spending more time on social media platforms had lower levels of body image satisfaction and self-esteem compared to those who reported less social media use. Moreover, the study found that comparing oneself to others on social media was a significant predictor of body image dissatisfaction and lower self-esteem.

Conclusion : These results suggest that social media use can have negative effects on body image satisfaction and self-esteem among young adults. It is important for individuals to be mindful of their social media use and to recognize the potential negative impact it can have on their mental health. Furthermore, interventions aimed at promoting positive body image and self-esteem should take into account the role of social media in shaping these attitudes and behaviors.

Importance of Research Results

Research results are important for several reasons, including:

• Advancing knowledge: Research results can contribute to the advancement of knowledge in a particular field, whether it be in science, technology, medicine, social sciences, or humanities.
• Developing theories: Research results can help to develop or modify existing theories and create new ones.
• Improving practices: Research results can inform and improve practices in various fields, such as education, healthcare, business, and public policy.
• Identifying problems and solutions: Research results can identify problems and provide solutions to complex issues in society, including issues related to health, environment, social justice, and economics.
• Validating claims : Research results can validate or refute claims made by individuals or groups in society, such as politicians, corporations, or activists.
• Providing evidence: Research results can provide evidence to support decision-making, policy-making, and resource allocation in various fields.

How to Write Results in A Research Paper

Here are some general guidelines on how to write results in a research paper:

• Organize the results section: Start by organizing the results section in a logical and coherent manner. Divide the section into subsections if necessary, based on the research questions or hypotheses.
• Present the findings: Present the findings in a clear and concise manner. Use tables, graphs, and figures to illustrate the data and make the presentation more engaging.
• Describe the data: Describe the data in detail, including the sample size, response rate, and any missing data. Provide relevant descriptive statistics such as means, standard deviations, and ranges.
• Interpret the findings: Interpret the findings in light of the research questions or hypotheses. Discuss the implications of the findings and the extent to which they support or contradict existing theories or previous research.
• Discuss the limitations : Discuss the limitations of the study, including any potential sources of bias or confounding factors that may have affected the results.
• Compare the results : Compare the results with those of previous studies or theoretical predictions. Discuss any similarities, differences, or inconsistencies.
• Avoid redundancy: Avoid repeating information that has already been presented in the introduction or methods sections. Instead, focus on presenting new and relevant information.
• Be objective: Be objective in presenting the results, avoiding any personal biases or interpretations.

When to Write Research Results

Here are situations When to Write Research Results”

• After conducting research on the chosen topic and obtaining relevant data, organize the findings in a structured format that accurately represents the information gathered.
• Once the data has been analyzed and interpreted, and conclusions have been drawn, begin the writing process.
• Before starting to write, ensure that the research results adhere to the guidelines and requirements of the intended audience, such as a scientific journal or academic conference.
• Begin by writing an abstract that briefly summarizes the research question, methodology, findings, and conclusions.
• Follow the abstract with an introduction that provides context for the research, explains its significance, and outlines the research question and objectives.
• The next section should be a literature review that provides an overview of existing research on the topic and highlights the gaps in knowledge that the current research seeks to address.
• The methodology section should provide a detailed explanation of the research design, including the sample size, data collection methods, and analytical techniques used.
• Present the research results in a clear and concise manner, using graphs, tables, and figures to illustrate the findings.
• Discuss the implications of the research results, including how they contribute to the existing body of knowledge on the topic and what further research is needed.
• Conclude the paper by summarizing the main findings, reiterating the significance of the research, and offering suggestions for future research.

Purpose of Research Results

The purposes of Research Results are as follows:

• Informing policy and practice: Research results can provide evidence-based information to inform policy decisions, such as in the fields of healthcare, education, and environmental regulation. They can also inform best practices in fields such as business, engineering, and social work.
• Addressing societal problems : Research results can be used to help address societal problems, such as reducing poverty, improving public health, and promoting social justice.
• Generating economic benefits : Research results can lead to the development of new products, services, and technologies that can create economic value and improve quality of life.
• Supporting academic and professional development : Research results can be used to support academic and professional development by providing opportunities for students, researchers, and practitioners to learn about new findings and methodologies in their field.
• Enhancing public understanding: Research results can help to educate the public about important issues and promote scientific literacy, leading to more informed decision-making and better public policy.
• Evaluating interventions: Research results can be used to evaluate the effectiveness of interventions, such as treatments, educational programs, and social policies. This can help to identify areas where improvements are needed and guide future interventions.
• Contributing to scientific progress: Research results can contribute to the advancement of science by providing new insights and discoveries that can lead to new theories, methods, and techniques.
• Informing decision-making : Research results can provide decision-makers with the information they need to make informed decisions. This can include decision-making at the individual, organizational, or governmental levels.
• Fostering collaboration : Research results can facilitate collaboration between researchers and practitioners, leading to new partnerships, interdisciplinary approaches, and innovative solutions to complex problems.

Advantages of Research Results

Some Advantages of Research Results are as follows:

• Improved decision-making: Research results can help inform decision-making in various fields, including medicine, business, and government. For example, research on the effectiveness of different treatments for a particular disease can help doctors make informed decisions about the best course of treatment for their patients.
• Innovation : Research results can lead to the development of new technologies, products, and services. For example, research on renewable energy sources can lead to the development of new and more efficient ways to harness renewable energy.
• Economic benefits: Research results can stimulate economic growth by providing new opportunities for businesses and entrepreneurs. For example, research on new materials or manufacturing techniques can lead to the development of new products and processes that can create new jobs and boost economic activity.
• Improved quality of life: Research results can contribute to improving the quality of life for individuals and society as a whole. For example, research on the causes of a particular disease can lead to the development of new treatments and cures, improving the health and well-being of millions of people.

About the author

Muhammad Hassan

Researcher, Academic Writer, Web developer

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Reporting Research Results in APA Style | Tips & Examples

Published on December 21, 2020 by Pritha Bhandari . Revised on January 17, 2024.

The results section of a quantitative research paper is where you summarize your data and report the findings of any relevant statistical analyses.

The APA manual provides rigorous guidelines for what to report in quantitative research papers in the fields of psychology, education, and other social sciences.

Use these standards to answer your research questions and report your data analyses in a complete and transparent way.

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Table of contents

What goes in your results section, introduce your data, summarize your data, report statistical results, presenting numbers effectively, what doesn’t belong in your results section, frequently asked questions about results in apa.

In APA style, the results section includes preliminary information about the participants and data, descriptive and inferential statistics, and the results of any exploratory analyses.

Include these in your results section:

• Participant flow and recruitment period. Report the number of participants at every stage of the study, as well as the dates when recruitment took place.
• Missing data . Identify the proportion of data that wasn’t included in your final analysis and state the reasons.
• Any adverse events. Make sure to report any unexpected events or side effects (for clinical studies).
• Descriptive statistics . Summarize the primary and secondary outcomes of the study.
• Inferential statistics , including confidence intervals and effect sizes. Address the primary and secondary research questions by reporting the detailed results of your main analyses.
• Results of subgroup or exploratory analyses, if applicable. Place detailed results in supplementary materials.

Write up the results in the past tense because you’re describing the outcomes of a completed research study.

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Before diving into your research findings, first describe the flow of participants at every stage of your study and whether any data were excluded from the final analysis.

Participant flow and recruitment period

It’s necessary to report any attrition, which is the decline in participants at every sequential stage of a study. That’s because an uneven number of participants across groups sometimes threatens internal validity and makes it difficult to compare groups. Be sure to also state all reasons for attrition.

If your study has multiple stages (e.g., pre-test, intervention, and post-test) and groups (e.g., experimental and control groups), a flow chart is the best way to report the number of participants in each group per stage and reasons for attrition.

Also report the dates for when you recruited participants or performed follow-up sessions.

Missing data

Another key issue is the completeness of your dataset. It’s necessary to report both the amount and reasons for data that was missing or excluded.

Data can become unusable due to equipment malfunctions, improper storage, unexpected events, participant ineligibility, and so on. For each case, state the reason why the data were unusable.

Some data points may be removed from the final analysis because they are outliers—but you must be able to justify how you decided what to exclude.

If you applied any techniques for overcoming or compensating for lost data, report those as well.

Adverse events

For clinical studies, report all events with serious consequences or any side effects that occured.

Descriptive statistics summarize your data for the reader. Present descriptive statistics for each primary, secondary, and subgroup analysis.

Don’t provide formulas or citations for commonly used statistics (e.g., standard deviation) – but do provide them for new or rare equations.

Descriptive statistics

The exact descriptive statistics that you report depends on the types of data in your study. Categorical variables can be reported using proportions, while quantitative data can be reported using means and standard deviations . For a large set of numbers, a table is the most effective presentation format.

Include sample sizes (overall and for each group) as well as appropriate measures of central tendency and variability for the outcomes in your results section. For every point estimate , add a clearly labelled measure of variability as well.

Be sure to note how you combined data to come up with variables of interest. For every variable of interest, explain how you operationalized it.

According to APA journal standards, it’s necessary to report all relevant hypothesis tests performed, estimates of effect sizes, and confidence intervals.

When reporting statistical results, you should first address primary research questions before moving onto secondary research questions and any exploratory or subgroup analyses.

Present the results of tests in the order that you performed them—report the outcomes of main tests before post-hoc tests, for example. Don’t leave out any relevant results, even if they don’t support your hypothesis.

Inferential statistics

For each statistical test performed, first restate the hypothesis , then state whether your hypothesis was supported and provide the outcomes that led you to that conclusion.

Report the following for each hypothesis test:

• the test statistic value,
• the degrees of freedom ,
• the exact p- value (unless it is less than 0.001),
• the magnitude and direction of the effect.

When reporting complex data analyses, such as factor analysis or multivariate analysis, present the models estimated in detail, and state the statistical software used. Make sure to report any violations of statistical assumptions or problems with estimation.

Effect sizes and confidence intervals

For each hypothesis test performed, you should present confidence intervals and estimates of effect sizes .

Confidence intervals are useful for showing the variability around point estimates. They should be included whenever you report population parameter estimates.

Effect sizes indicate how impactful the outcomes of a study are. But since they are estimates, it’s recommended that you also provide confidence intervals of effect sizes.

Subgroup or exploratory analyses

Briefly report the results of any other planned or exploratory analyses you performed. These may include subgroup analyses as well.

Subgroup analyses come with a high chance of false positive results, because performing a large number of comparison or correlation tests increases the chances of finding significant results.

If you find significant results in these analyses, make sure to appropriately report them as exploratory (rather than confirmatory) results to avoid overstating their importance.

While these analyses can be reported in less detail in the main text, you can provide the full analyses in supplementary materials.

Prevent plagiarism. Run a free check.

To effectively present numbers, use a mix of text, tables , and figures where appropriate:

• To present three or fewer numbers, try a sentence ,
• To present between 4 and 20 numbers, try a table ,
• To present more than 20 numbers, try a figure .

Since these are general guidelines, use your own judgment and feedback from others for effective presentation of numbers.

Tables and figures should be numbered and have titles, along with relevant notes. Make sure to present data only once throughout the paper and refer to any tables and figures in the text.

Formatting statistics and numbers

It’s important to follow capitalization , italicization, and abbreviation rules when referring to statistics in your paper. There are specific format guidelines for reporting statistics in APA , as well as general rules about writing numbers .

If you are unsure of how to present specific symbols, look up the detailed APA guidelines or other papers in your field.

It’s important to provide a complete picture of your data analyses and outcomes in a concise way. For that reason, raw data and any interpretations of your results are not included in the results section.

It’s rarely appropriate to include raw data in your results section. Instead, you should always save the raw data securely and make them available and accessible to any other researchers who request them.

Making scientific research available to others is a key part of academic integrity and open science.

Interpretation or discussion of results

This belongs in your discussion section. Your results section is where you objectively report all relevant findings and leave them open for interpretation by readers.

While you should state whether the findings of statistical tests lend support to your hypotheses, refrain from forming conclusions to your research questions in the results section.

Explanation of how statistics tests work

For the sake of concise writing, you can safely assume that readers of your paper have professional knowledge of how statistical inferences work.

In an APA results section , you should generally report the following:

• Participant flow and recruitment period.
• Missing data and any adverse events.
• Descriptive statistics about your samples.
• Inferential statistics , including confidence intervals and effect sizes.
• Results of any subgroup or exploratory analyses, if applicable.

According to the APA guidelines, you should report enough detail on inferential statistics so that your readers understand your analyses.

• the test statistic value
• the degrees of freedom
• the exact p value (unless it is less than 0.001)
• the magnitude and direction of the effect

You should also present confidence intervals and estimates of effect sizes where relevant.

In APA style, statistics can be presented in the main text or as tables or figures . To decide how to present numbers, you can follow APA guidelines:

• To present three or fewer numbers, try a sentence,
• To present between 4 and 20 numbers, try a table,
• To present more than 20 numbers, try a figure.

Results are usually written in the past tense , because they are describing the outcome of completed actions.

The results chapter or section simply and objectively reports what you found, without speculating on why you found these results. The discussion interprets the meaning of the results, puts them in context, and explains why they matter.

In qualitative research , results and discussion are sometimes combined. But in quantitative research , it’s considered important to separate the objective results from your interpretation of them.

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How to Write the Discussion Section of a Research Paper

The discussion section of a research paper analyzes and interprets the findings, provides context, compares them with previous studies, identifies limitations, and suggests future research directions.

Updated on September 15, 2023

Structure your discussion section right, and you’ll be cited more often while doing a greater service to the scientific community. So, what actually goes into the discussion section? And how do you write it?

The discussion section of your research paper is where you let the reader know how your study is positioned in the literature, what to take away from your paper, and how your work helps them. It can also include your conclusions and suggestions for future studies.

First, we’ll define all the parts of your discussion paper, and then look into how to write a strong, effective discussion section for your paper or manuscript.

Discussion section: what is it, what it does

The discussion section comes later in your paper, following the introduction, methods, and results. The discussion sets up your study’s conclusions. Its main goals are to present, interpret, and provide a context for your results.

What is it?

The discussion section provides an analysis and interpretation of the findings, compares them with previous studies, identifies limitations, and suggests future directions for research.

This section combines information from the preceding parts of your paper into a coherent story. By this point, the reader already knows why you did your study (introduction), how you did it (methods), and what happened (results). In the discussion, you’ll help the reader connect the ideas from these sections.

Why is it necessary?

The discussion provides context and interpretations for the results. It also answers the questions posed in the introduction. While the results section describes your findings, the discussion explains what they say. This is also where you can describe the impact or implications of your research.

Adds context for your results

Most research studies aim to answer a question, replicate a finding, or address limitations in the literature. These goals are first described in the introduction. However, in the discussion section, the author can refer back to them to explain how the study's objective was achieved. 

Shows what your results actually mean and real-world implications

The discussion can also describe the effect of your findings on research or practice. How are your results significant for readers, other researchers, or policymakers?

What to include in your discussion (in the correct order)

A complete and effective discussion section should at least touch on the points described below.

Summary of key findings

The discussion should begin with a brief factual summary of the results. Concisely overview the main results you obtained.

Begin with key findings with supporting evidence

Your results section described a list of findings, but what message do they send when you look at them all together?

Your findings were detailed in the results section, so there’s no need to repeat them here, but do provide at least a few highlights. This will help refresh the reader’s memory and help them focus on the big picture.

Read the first paragraph of the discussion section in this article (PDF) for an example of how to start this part of your paper. Notice how the authors break down their results and follow each description sentence with an explanation of why each finding is relevant. 

State clearly and concisely

Following a clear and direct writing style is especially important in the discussion section. After all, this is where you will make some of the most impactful points in your paper. While the results section often contains technical vocabulary, such as statistical terms, the discussion section lets you describe your findings more clearly. 

Interpretation of results

Once you’ve given your reader an overview of your results, you need to interpret those results. In other words, what do your results mean? Discuss the findings’ implications and significance in relation to your research question or hypothesis.

Analyze and interpret your findings

Look into your findings and explore what’s behind them or what may have caused them. If your introduction cited theories or studies that could explain your findings, use these sources as a basis to discuss your results.

For example, look at the second paragraph in the discussion section of this article on waggling honey bees. Here, the authors explore their results based on information from the literature.

Unexpected or contradictory results

Sometimes, your findings are not what you expect. Here’s where you describe this and try to find a reason for it. Could it be because of the method you used? Does it have something to do with the variables analyzed? Comparing your methods with those of other similar studies can help with this task.

Context and comparison with previous work

Refer to related studies to place your research in a larger context and the literature. Compare and contrast your findings with existing literature, highlighting similarities, differences, and/or contradictions.

How your work compares or contrasts with previous work

Studies with similar findings to yours can be cited to show the strength of your findings. Information from these studies can also be used to help explain your results. Differences between your findings and others in the literature can also be discussed here. 

How to divide this section into subsections

If you have more than one objective in your study or many key findings, you can dedicate a separate section to each of these. Here’s an example of this approach. You can see that the discussion section is divided into topics and even has a separate heading for each of them. 

Limitations

Many journals require you to include the limitations of your study in the discussion. Even if they don’t, there are good reasons to mention these in your paper.

Why limitations don’t have a negative connotation

A study’s limitations are points to be improved upon in future research. While some of these may be flaws in your method, many may be due to factors you couldn’t predict.

Examples include time constraints or small sample sizes. Pointing this out will help future researchers avoid or address these issues. This part of the discussion can also include any attempts you have made to reduce the impact of these limitations, as in this study .

How limitations add to a researcher's credibility

Pointing out the limitations of your study demonstrates transparency. It also shows that you know your methods well and can conduct a critical assessment of them.  

Implications and significance

The final paragraph of the discussion section should contain the take-home messages for your study. It can also cite the “strong points” of your study, to contrast with the limitations section.

Restate your hypothesis

Remind the reader what your hypothesis was before you conducted the study. 

How was it proven or disproven?

Identify your main findings and describe how they relate to your hypothesis.

How your results contribute to the literature

Were you able to answer your research question? Or address a gap in the literature?

Future implications of your research

Describe the impact that your results may have on the topic of study. Your results may show, for instance, that there are still limitations in the literature for future studies to address. There may be a need for studies that extend your findings in a specific way. You also may need additional research to corroborate your findings. 

Sample discussion section

This fictitious example covers all the aspects discussed above. Your actual discussion section will probably be much longer, but you can read this to get an idea of everything your discussion should cover.

Our results showed that the presence of cats in a household is associated with higher levels of perceived happiness by its human occupants. These findings support our hypothesis and demonstrate the association between pet ownership and well-being. 

The present findings align with those of Bao and Schreer (2016) and Hardie et al. (2023), who observed greater life satisfaction in pet owners relative to non-owners. Although the present study did not directly evaluate life satisfaction, this factor may explain the association between happiness and cat ownership observed in our sample.

Our findings must be interpreted in light of some limitations, such as the focus on cat ownership only rather than pets as a whole. This may limit the generalizability of our results.

Nevertheless, this study had several strengths. These include its strict exclusion criteria and use of a standardized assessment instrument to investigate the relationships between pets and owners. These attributes bolster the accuracy of our results and reduce the influence of confounding factors, increasing the strength of our conclusions. Future studies may examine the factors that mediate the association between pet ownership and happiness to better comprehend this phenomenon.

This brief discussion begins with a quick summary of the results and hypothesis. The next paragraph cites previous research and compares its findings to those of this study. Information from previous studies is also used to help interpret the findings. After discussing the results of the study, some limitations are pointed out. The paper also explains why these limitations may influence the interpretation of results. Then, final conclusions are drawn based on the study, and directions for future research are suggested.

How to make your discussion flow naturally

If you find writing in scientific English challenging, the discussion and conclusions are often the hardest parts of the paper to write. That’s because you’re not just listing up studies, methods, and outcomes. You’re actually expressing your thoughts and interpretations in words.

• How formal should it be?
• What words should you use, or not use?
• How do you meet strict word limits, or make it longer and more informative?

Always give it your best, but sometimes a helping hand can, well, help. Getting a professional edit can help clarify your work’s importance while improving the English used to explain it. When readers know the value of your work, they’ll cite it. We’ll assign your study to an expert editor knowledgeable in your area of research. Their work will clarify your discussion, helping it to tell your story. Find out more about AJE Editing.

Adam Goulston, PsyD, MS, MBA, MISD, ELS

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Academic Phrases for Writing Results & Discussion Sections of a Research Paper

Overview |   Abstract   | Introduction | Literature Review | Materials & Methods | Results & Discussion | Conclusion & Future Work | Acknowledgements & Appendix

The results and discussion sections are one of the challenging sections to write. It is important to plan this section carefully as it may contain a large amount of scientific data that needs to be presented in a clear and concise fashion. The purpose of a Results section is to present the key results of your research. Results and discussions can either be combined into one section or organized as separate sections depending on the requirements of the journal to which you are submitting your research paper. Use subsections and subheadings to improve readability and clarity. Number all tables and figures with descriptive titles. Present your results as figures and tables and point the reader to relevant items while discussing the results. This section should highlight significant or interesting findings along with P values for statistical tests. Be sure to include negative results and highlight potential limitations of the paper. You will be criticised by the reviewers if you don’t discuss the shortcomings of your research. This often makes up for a great discussion section, so do not be afraid to highlight them.

The results and discussion section of your research paper should include the following:

• Comparison with prior studies
• Limitations of your work
• Casual arguments
• Speculations
• Deductive arguments

1. Findings

From the short review above, key findings emerge: __ We describe the results of __, which show __ This suggests that __ We showed that __ Our findings on __ at least hint that __ This is an important finding in the understanding of the __ The present study confirmed the findings about __ Another promising finding was that __ Our results demonstrated that __ This result highlights that little is known about the __ A further novel finding is that __ Together, the present findings confirm __ The implications of these findings are discussed in __ The results demonstrate two things.  First, __. Second,  __ The results of the experiment found clear support for the __ This analysis found evidence for __ Planned comparisons revealed that __ Our results casts a new light on __ This section summarises the findings and contributions made. It performs well, giving good results. This gives clearly better results than __ The results confirm that this a good choice for __ From the results, it is clear that __ In this section, we will illustrate some experimental results. This delivers significantly better results due to __ The result now provides evidence to __ It leads to good results, even if the improvement is negligible. This yields increasingly good results on data. The result of this analysis is then compared with the  __ The applicability of these new results are then tested on __ This is important to correctly interpret the results. The results are substantially better than __ The results lead to similar conclusion where __ Superior results are seen for __ From these results it is clear that __ Extensive results carried out show that this method improves __ We obtain good results with this simple method. However, even better results are achieved when using our algorithm. It is worth discussing these interesting facts revealed by the results of  __ Overall, our method was the one that obtained the most robust results. Slightly superior results are achieved with our algorithm. The result is equal to or better than a result that is currently accepted.

2. Comparison with prior studies

The results demonstrated in this chapter match state of the art methods. Here we compare the results of the proposed method with those of the traditional methods. These results go beyond previous reports, showing that __ In line with previous studies __ This result ties well with previous studies wherein __ Contrary to the findings of __ we did not find __ They have demonstrated that __ Others have shown that __ improves __ By comparing the results from __, we hope to determine __ However, in line with the ideas of __, it can be concluded that __ When comparing our results to those of older studies, it must be pointed out that __ We have verified that using __ produces similar results Overall these findings are in accordance with findings reported by __ Even though we did not replicate the previously reported __, our results suggest that __ A similar conclusion was reached by __ However, when comparing our results to those of older studies, it must be pointed out __ This is consistent with what has been found in previous __ A similar pattern of results was obtained in __ The findings are directly in line with previous findings These basic findings are consistent with research showing that __ Other results were broadly in line with __

3. Limitations of your work

Because of the lack of __ we decided to not investigate __ One concern about the findings of __ was that __ Because of this potential limitation, we treat __ The limitations of the present studies naturally include __ Regarding the limitations of __, it could be argued that __ Another limitation of this __ This limitation is apparent in many __ Another limitation in __ involves the issue of __ The main limitation is the lack of __ One limitation is found in this case. One limitation of these methods however is that they __ It presents some limitations such as __ Although widely accepted, it suffers from some limitations due to __ An apparent limitation of the method is __ There are several limitations to this approach. One limitation of our implementation is that it is __ A major source of limitation is due to  __ The approach utilised suffers from the limitation that __ The limitations are becoming clear __ It suffers from the same limitations associated with a __

4. Casual arguments

A popular explanation of __ is that __ It is by now generally accepted that __ A popular explanation is that __ As it is not generally agreed that __ These are very small and difficult to observe. It is important to highlight the fact that __ It is notable that __ An important question associated with __ is __ This did not impair the __ This is important because there is __ This implies that __ is associated with __ This is indicative for lack of __ This will not be biased by __ There were also some important differences in __ It is interesting to note that, __ It is unlikely that __ This may alter or improve aspects of __ In contrast, this makes it possible to __ This is particularly important when investigating __ This has been used to successfully account for __ This introduces a possible confound in __ This was included to verify that __

5. Speculations

However, we acknowledge that there are considerable discussions among researchers as to __ We speculate that this might be due to __ There are reasons to doubt this explanation of __ It remains unclear to which degree __ are attributed to __ However, __ does seem to improve __ This does seem to depend on __ It is important to note, that the present evidence relies on __ The results show that __ does not seem to impact the __ However, the extent to which it is possible to __ is unknown Alternatively, it could simply mean that __ It is difficult to explain such results within the context of __ It is unclear whether this is a suitable for __ This appears to be a case of __ From this standpoint, __ can be considered as __ To date, __remain unknown Under certain assumptions, this can be construed as __ Because of this potential limitation, we treat __ In addition, several questions remain unanswered. At this stage of understanding, we believe__ Therefore, it remains unclear whether __ This may explain why __

6. Deductive arguments

A difference between these __ can only be attributable to __ Nonetheless, we believe that it is well justified to __ This may raise concerns about __ which can be addressed by __ As discussed, this is due to the fact that __ Results demonstrate that this is not necessarily true. These findings support the notion that __ is not influenced by __ This may be the reason why we did not find __ In order to test whether this is equivalent across __, we __ Therefore, __ can be considered to be equivalent for __

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Writing a scientific paper.

• Writing a lab report
• INTRODUCTION

Writing a "good" results section

Figures and Captions in Lab Reports

"Results Checklist" from: How to Write a Good Scientific Paper. Chris A. Mack. SPIE. 2018.

Additional tips for results sections.

• LITERATURE CITED
• Bibliography of guides to scientific writing and presenting
• Peer Review
• Presentations
• Lab Report Writing Guides on the Web

This is the core of the paper. Don't start the results sections with methods you left out of the Materials and Methods section. You need to give an overall description of the experiments and present the data you found.

• Factual statements supported by evidence. Short and sweet without excess words
• Present representative data rather than endlessly repetitive data
• Discuss variables only if they had an effect (positive or negative)
• Use meaningful statistics
• Avoid redundancy. If it is in the tables or captions you may not need to repeat it

A short article by Dr. Brett Couch and Dr. Deena Wassenberg, Biology Program, University of Minnesota

• Present the results of the paper, in logical order, using tables and graphs as necessary.
• Explain the results and show how they help to answer the research questions posed in the Introduction. Evidence does not explain itself; the results must be presented and then explained. 
• Avoid: presenting results that are never discussed;  presenting results in chronological order rather than logical order; ignoring results that do not support the conclusions; 
• Number tables and figures separately beginning with 1 (i.e. Table 1, Table 2, Figure 1, etc.).
• Do not attempt to evaluate the results in this section. Report only what you found; hold all discussion of the significance of the results for the Discussion section.
• It is not necessary to describe every step of your statistical analyses. Scientists understand all about null hypotheses, rejection rules, and so forth and do not need to be reminded of them. Just say something like, "Honeybees did not use the flowers in proportion to their availability (X2 = 7.9, p<0.05, d.f.= 4, chi-square test)." Likewise, cite tables and figures without describing in detail how the data were manipulated. Explanations of this sort should appear in a legend or caption written on the same page as the figure or table.
• You must refer in the text to each figure or table you include in your paper.
• Tables generally should report summary-level data, such as means ± standard deviations, rather than all your raw data.  A long list of all your individual observations will mean much less than a few concise, easy-to-read tables or figures that bring out the main findings of your study.  
• Only use a figure (graph) when the data lend themselves to a good visual representation.  Avoid using figures that show too many variables or trends at once, because they can be hard to understand.

From:  https://writingcenter.gmu.edu/guides/imrad-results-discussion

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How to Write a Discussion Section for a Research Paper

We’ve talked about several useful writing tips that authors should consider while drafting or editing their research papers. In particular, we’ve focused on  figures and legends , as well as the Introduction ,  Methods , and  Results . Now that we’ve addressed the more technical portions of your journal manuscript, let’s turn to the analytical segments of your research article. In this article, we’ll provide tips on how to write a strong Discussion section that best portrays the significance of your research contributions.

What is the Discussion section of a research paper?

In a nutshell,  your Discussion fulfills the promise you made to readers in your Introduction . At the beginning of your paper, you tell us why we should care about your research. You then guide us through a series of intricate images and graphs that capture all the relevant data you collected during your research. We may be dazzled and impressed at first, but none of that matters if you deliver an anti-climactic conclusion in the Discussion section!

Are you feeling pressured? Don’t worry. To be honest, you will edit the Discussion section of your manuscript numerous times. After all, in as little as one to two paragraphs ( Nature ‘s suggestion  based on their 3,000-word main body text limit), you have to explain how your research moves us from point A (issues you raise in the Introduction) to point B (our new understanding of these matters). You must also recommend how we might get to point C (i.e., identify what you think is the next direction for research in this field). That’s a lot to say in two paragraphs!

So, how do you do that? Let’s take a closer look.

What should I include in the Discussion section?

As we stated above, the goal of your Discussion section is to  answer the questions you raise in your Introduction by using the results you collected during your research . The content you include in the Discussions segment should include the following information:

• Remind us why we should be interested in this research project.
• Describe the nature of the knowledge gap you were trying to fill using the results of your study.
• Don’t repeat your Introduction. Instead, focus on why  this  particular study was needed to fill the gap you noticed and why that gap needed filling in the first place.
• Mainly, you want to remind us of how your research will increase our knowledge base and inspire others to conduct further research.
• Clearly tell us what that piece of missing knowledge was.
• Answer each of the questions you asked in your Introduction and explain how your results support those conclusions.
• Make sure to factor in all results relevant to the questions (even if those results were not statistically significant).
• Focus on the significance of the most noteworthy results.
• If conflicting inferences can be drawn from your results, evaluate the merits of all of them.
• Don’t rehash what you said earlier in the Results section. Rather, discuss your findings in the context of answering your hypothesis. Instead of making statements like “[The first result] was this…,” say, “[The first result] suggests [conclusion].”
• Do your conclusions line up with existing literature?
• Discuss whether your findings agree with current knowledge and expectations.
• Keep in mind good persuasive argument skills, such as explaining the strengths of your arguments and highlighting the weaknesses of contrary opinions.
• If you discovered something unexpected, offer reasons. If your conclusions aren’t aligned with current literature, explain.
• Address any limitations of your study and how relevant they are to interpreting your results and validating your findings.
• Make sure to acknowledge any weaknesses in your conclusions and suggest room for further research concerning that aspect of your analysis.
• Make sure your suggestions aren’t ones that should have been conducted during your research! Doing so might raise questions about your initial research design and protocols.
• Similarly, maintain a critical but unapologetic tone. You want to instill confidence in your readers that you have thoroughly examined your results and have objectively assessed them in a way that would benefit the scientific community’s desire to expand our knowledge base.
• Recommend next steps.
• Your suggestions should inspire other researchers to conduct follow-up studies to build upon the knowledge you have shared with them.
• Keep the list short (no more than two).

How to Write the Discussion Section

The above list of what to include in the Discussion section gives an overall idea of what you need to focus on throughout the section. Below are some tips and general suggestions about the technical aspects of writing and organization that you might find useful as you draft or revise the contents we’ve outlined above.

Technical writing elements

• Embrace active voice because it eliminates the awkward phrasing and wordiness that accompanies passive voice.
• Use the present tense, which should also be employed in the Introduction.
• Sprinkle with first person pronouns if needed, but generally, avoid it. We want to focus on your findings.
• Maintain an objective and analytical tone.

Discussion section organization

• Keep the same flow across the Results, Methods, and Discussion sections.
• We develop a rhythm as we read and parallel structures facilitate our comprehension. When you organize information the same way in each of these related parts of your journal manuscript, we can quickly see how a certain result was interpreted and quickly verify the particular methods used to produce that result.
• Notice how using parallel structure will eliminate extra narration in the Discussion part since we can anticipate the flow of your ideas based on what we read in the Results segment. Reducing wordiness is important when you only have a few paragraphs to devote to the Discussion section!
• Within each subpart of a Discussion, the information should flow as follows: (A) conclusion first, (B) relevant results and how they relate to that conclusion and (C) relevant literature.
• End with a concise summary explaining the big-picture impact of your study on our understanding of the subject matter. At the beginning of your Discussion section, you stated why  this  particular study was needed to fill the gap you noticed and why that gap needed filling in the first place. Now, it is time to end with “how your research filled that gap.”

Discussion Part 1: Summarizing Key Findings

Begin the Discussion section by restating your  statement of the problem  and briefly summarizing the major results. Do not simply repeat your findings. Rather, try to create a concise statement of the main results that directly answer the central research question that you stated in the Introduction section . This content should not be longer than one paragraph in length.

Many researchers struggle with understanding the precise differences between a Discussion section and a Results section . The most important thing to remember here is that your Discussion section should subjectively evaluate the findings presented in the Results section, and in relatively the same order. Keep these sections distinct by making sure that you do not repeat the findings without providing an interpretation.

Phrase examples: Summarizing the results

• The findings indicate that …
• These results suggest a correlation between A and B …
• The data present here suggest that …
• An interpretation of the findings reveals a connection between…

Discussion Part 2: Interpreting the Findings

What do the results mean? It may seem obvious to you, but simply looking at the figures in the Results section will not necessarily convey to readers the importance of the findings in answering your research questions.

The exact structure of interpretations depends on the type of research being conducted. Here are some common approaches to interpreting data:

• Identifying correlations and relationships in the findings
• Explaining whether the results confirm or undermine your research hypothesis
• Giving the findings context within the history of similar research studies
• Discussing unexpected results and analyzing their significance to your study or general research
• Offering alternative explanations and arguing for your position

Organize the Discussion section around key arguments, themes, hypotheses, or research questions or problems. Again, make sure to follow the same order as you did in the Results section.

Discussion Part 3: Discussing the Implications

In addition to providing your own interpretations, show how your results fit into the wider scholarly literature you surveyed in the  literature review section. This section is called the implications of the study . Show where and how these results fit into existing knowledge, what additional insights they contribute, and any possible consequences that might arise from this knowledge, both in the specific research topic and in the wider scientific domain.

Questions to ask yourself when dealing with potential implications:

• Do your findings fall in line with existing theories, or do they challenge these theories or findings? What new information do they contribute to the literature, if any? How exactly do these findings impact or conflict with existing theories or models?
• What are the practical implications on actual subjects or demographics?
• What are the methodological implications for similar studies conducted either in the past or future?

Your purpose in giving the implications is to spell out exactly what your study has contributed and why researchers and other readers should be interested.

Phrase examples: Discussing the implications of the research

• These results confirm the existing evidence in X studies…
• The results are not in line with the foregoing theory that…
• This experiment provides new insights into the connection between…
• These findings present a more nuanced understanding of…
• While previous studies have focused on X, these results demonstrate that Y.

Step 4: Acknowledging the limitations

All research has study limitations of one sort or another. Acknowledging limitations in methodology or approach helps strengthen your credibility as a researcher. Study limitations are not simply a list of mistakes made in the study. Rather, limitations help provide a more detailed picture of what can or cannot be concluded from your findings. In essence, they help temper and qualify the study implications you listed previously.

Study limitations can relate to research design, specific methodological or material choices, or unexpected issues that emerged while you conducted the research. Mention only those limitations directly relate to your research questions, and explain what impact these limitations had on how your study was conducted and the validity of any interpretations.

Possible types of study limitations:

• Insufficient sample size for statistical measurements
• Lack of previous research studies on the topic
• Methods/instruments/techniques used to collect the data
• Limited access to data
• Time constraints in properly preparing and executing the study

After discussing the study limitations, you can also stress that your results are still valid. Give some specific reasons why the limitations do not necessarily handicap your study or narrow its scope.

Phrase examples: Limitations sentence beginners

• “There may be some possible limitations in this study.”
• “The findings of this study have to be seen in light of some limitations.”
•  “The first limitation is the…The second limitation concerns the…”
•  “The empirical results reported herein should be considered in the light of some limitations.”
• “This research, however, is subject to several limitations.”
• “The primary limitation to the generalization of these results is…”
• “Nonetheless, these results must be interpreted with caution and a number of limitations should be borne in mind.”

Discussion Part 5: Giving Recommendations for Further Research

Based on your interpretation and discussion of the findings, your recommendations can include practical changes to the study or specific further research to be conducted to clarify the research questions. Recommendations are often listed in a separate Conclusion section , but often this is just the final paragraph of the Discussion section.

Suggestions for further research often stem directly from the limitations outlined. Rather than simply stating that “further research should be conducted,” provide concrete specifics for how future can help answer questions that your research could not.

Phrase examples: Recommendation sentence beginners

• Further research is needed to establish …
• There is abundant space for further progress in analyzing…
• A further study with more focus on X should be done to investigate…
• Further studies of X that account for these variables must be undertaken.

Consider Receiving Professional Language Editing

As you edit or draft your research manuscript, we hope that you implement these guidelines to produce a more effective Discussion section. And after completing your draft, don’t forget to submit your work to a professional proofreading and English editing service like Wordvice, including our manuscript editing service for  paper editing , cover letter editing , SOP editing , and personal statement proofreading services. Language editors not only proofread and correct errors in grammar, punctuation, mechanics, and formatting but also improve terms and revise phrases so they read more naturally. Wordvice is an industry leader in providing high-quality revision for all types of academic documents.

For additional information about how to write a strong research paper, make sure to check out our full  research writing series !

Wordvice Writing Resources

• How to Write a Research Paper Introduction 
• Which Verb Tenses to Use in a Research Paper
• How to Write an Abstract for a Research Paper
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• Useful Phrases for Academic Writing
• Common Transition Terms in Academic Papers
• Active and Passive Voice in Research Papers
• 100+ Verbs That Will Make Your Research Writing Amazing
• Tips for Paraphrasing in Research Papers

Additional Academic Resources

•   Guide for Authors.  (Elsevier)
•  How to Write the Results Section of a Research Paper.  (Bates College)
•   Structure of a Research Paper.  (University of Minnesota Biomedical Library)
•   How to Choose a Target Journal  (Springer)
•   How to Write Figures and Tables  (UNC Writing Center)

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How to Write a Discussion Section: Writing Guide

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The discussion section of a research paper is where the author analyzes and explains the importance of the study's results. It presents the conclusions drawn from the study, compares them to previous research, and addresses any potential limitations or weaknesses. The discussion section should also suggest areas for future research.

Everything is not that complicated if you know where to find the required information. We’ll tell you everything there is to know about writing your discussion. Our easy guide covers all important bits, including research questions and your research results. Do you know how all enumerated events are connected? Well, you will after reading this guide we’ve prepared for you!

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Discussion Section of a Research Paper: Frequently Asked Questions

1. how long should the discussion section of a research paper be.

Our discussion section of a research paper should not be longer than other sections. So try to keep it short but as informative as possible. It usually contains around 6-7 paragraphs in length. It is enough to briefly summarize all the important data and not to drag it.

2. What's the difference between the discussion and the results?

The difference between discussion and results is very simple and easy to understand. The results only report your main findings. You stated what you have found and how you have done that. In contrast, one’s discussion mentions your findings and explains how they relate to other literature, research questions, and one’s hypothesis. Therefore, it is not only a report but an efficient as well as proper explanation.

3. What's the difference between a discussion and a conclusion?

The difference between discussion and conclusion is also quite easy. Conclusion is a brief summary of all the findings and results. Still, our favorite discussion section interprets and explains your main results. It is an important but more lengthy and wordy part. Besides, it uses extra literature for references.

4. What is the purpose of the discussion section?

The primary purpose of a discussion section is to interpret and describe all your interesting findings. Therefore, you should state what you have learned, whether your hypothesis was correct and how your results can be explained using other sources. If this section is clear to readers, our congratulations as you have succeeded.

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The discussion section of a research paper can be viewed as something similar to the conclusion of your paper. But not literal, of course. It’s an ultimate section where you can talk about the findings of your study. Think about these questions when writing:

So, answer your questions, provide proof, and don’t forget about your promises from the introduction. 

How to write the discussion section of a research paper is something everyone googles eventually. It's just life. But why not make everything easier? In brief, this section we’re talking about must include all following parts:

Indeed, all those parts may confuse anyone. So by looking at our guide, you'll save yourself some hassle.  P.S. All our steps are easy and explained in detail! But if you are looking for the most efficient solution, consider using professional help. Leave your “ write my research paper for me ” order at StudyCrumb and get a customized study tailored to your requirements.

First and foremost, how to start the discussion section of a research paper? Here’s what you should definitely consider before settling down to start writing:

Writing the discussion section of a research paper also involves mentioning your questions. Remember that in your introduction, you have promised your readers to answer certain questions. Well, now it’s a perfect time to finally give the awaited answer. You need to explain all possible correlations between your findings, research questions, and literature proposed. You already had hypotheses. So were they correct, or maybe you want to propose certain corrections? Section’s main goal is to avoid open ends. It’s not a story or a fairytale with an intriguing ending. If you have several questions, you must answer them. As simple as that.

Writing a discussion section of a research paper also requires any writer to explain their results. You will undoubtedly include an impactful literature review. However, your readers should not just try and struggle with understanding what are some specific relationships behind previous studies and your results.  Your results should sound something like: “This guy in their paper discovered that apples are green. Nevertheless, I have proven via experimentation and research that apples are actually red.” Please, don’t take these results directly. It’s just an initial hypothesis. But what you should definitely remember is any practical implications of your study. Why does it matter and how can anyone use it? That’s the most crucial question.

Discussion section of a research paper isn’t limitless. What does that mean? Essentially, it means that you also have to discuss any limitations of your study. Maybe you had some methodological inconsistencies. Possibly, there are no particular theories or not enough information for you to be entirely confident in one’s conclusions.  You might say that an available source of literature you have studied does not focus on one’s issue. That’s why one’s main limitation is theoretical. However, keep in mind that your limitations must possess a certain degree of relevancy. You can just say that you haven’t found enough books. Your information must be truthful to research.

Your last step when you write a discussion section in a paper is its conclusion, like in any other academic work. Writer’s conclusion must be as strong as their starting point of the overall work. Check out our brief list of things to know about the conclusion in research paper :

All the best example discussion sections of a research paper will be written according to our brief guide. Don’t forget that you need to state your findings and underline the importance of your work. An undoubtedly big part of one’s discussion will definitely be answering and explaining the research questions. In other words, you’ll already have all the knowledge you have so carefully gathered. Our last step for you is to recollect and wrap up your paper. But we’re sure you’ll succeed!

Today we have covered how to write a discussion section. That was quite a brief journey, wasn’t it? Just to remind you to focus on these things:

But, wait, this guide is not the only thing we can do. Looking for how to write an abstract for a research paper  for example? We have such a blog and much more on our platform.

• Did you answer all of the promised research questions?
• Did you mention why your work matters?
• What are your findings, and why should anyone even care?
• Does your study have a literature review?
• Answers for research questions
• Literature review
• Results of the work
• Limitations of one’s study
• Overall conclusion
• All essays or papers must begin strong. All readers will not wait for any writer to get to the point. We advise summarizing the paper's main findings.
• Moreover, you should relate both discussion and literature review to what you have discovered. Mentioning that would be a plus too.
• Make sure that an introduction or start per se is clear and concise. Word count might be needed for school. But any paper should be understandable and not too diluted.
• It must present its scientific relevance and importance of your work.
• It should include different implications of your research.
• It should not, however, discuss anything new or things that you have not mentioned before.
• Leave no open questions and carefully complete the work without them.
• Importance of your study.
• Summary of the information you have gathered.
• Main findings and conclusions.
• Answers to all research questions without an open end.
• Correlation between literature review and your results.

What Is in the Discussion Section of a Research Paper

How to write a discussion section in 5 steps, step 1. start strong: discussion section of a research paper, step 2. answer the questions in your discussion section of a research paper, step 3. relate your results in a discussion section, step 4. describe the limitations in your discussion section, step 5. conclude your discussion section with recommendations, discussion section of a research paper example, how to write a discussion section: final thoughts.

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General Research Paper Guidelines: Discussion

Discussion section.

The overall purpose of a research paper’s discussion section is to evaluate and interpret results, while explaining both the implications and limitations of your findings. Per APA (2020) guidelines, this section requires you to “examine, interpret, and qualify the results and draw inferences and conclusions from them” (p. 89). Discussion sections also require you to detail any new insights, think through areas for future research, highlight the work that still needs to be done to further your topic, and provide a clear conclusion to your research paper. In a good discussion section, you should do the following:

• Clearly connect the discussion of your results to your introduction, including your central argument, thesis, or problem statement.
• Provide readers with a critical thinking through of your results, answering the “so what?” question about each of your findings. In other words, why is this finding important?
• Detail how your research findings might address critical gaps or problems in your field
• Compare your results to similar studies’ findings
• Provide the possibility of alternative interpretations, as your goal as a researcher is to “discover” and “examine” and not to “prove” or “disprove.” Instead of trying to fit your results into your hypothesis, critically engage with alternative interpretations to your results.

For more specific details on your Discussion section, be sure to review Sections 3.8 (pp. 89-90) and 3.16 (pp. 103-104) of your 7 th edition APA manual

*Box content adapted from:

University of Southern California (n.d.). Organizing your social sciences research paper: 8 the discussion . https://libguides.usc.edu/writingguide/discussion

Limitations

Limitations of generalizability or utility of findings, often over which the researcher has no control, should be detailed in your Discussion section. Including limitations for your reader allows you to demonstrate you have thought critically about your given topic, understood relevant literature addressing your topic, and chosen the methodology most appropriate for your research. It also allows you an opportunity to suggest avenues for future research on your topic. An effective limitations section will include the following:

• Detail (a) sources of potential bias, (b) possible imprecision of measures, (c) other limitations or weaknesses of the study, including any methodological or researcher limitations.
• Sample size: In quantitative research, if a sample size is too small, it is more difficult to generalize results.
• Lack of available/reliable data : In some cases, data might not be available or reliable, which will ultimately affect the overall scope of your research. Use this as an opportunity to explain areas for future study.
• Lack of prior research on your study topic: In some cases, you might find that there is very little or no similar research on your study topic, which hinders the credibility and scope of your own research. If this is the case, use this limitation as an opportunity to call for future research. However, make sure you have done a thorough search of the available literature before making this claim.
• Flaws in measurement of data: Hindsight is 20/20, and you might realize after you have completed your research that the data tool you used actually limited the scope or results of your study in some way. Again, acknowledge the weakness and use it as an opportunity to highlight areas for future study.
• Limits of self-reported data: In your research, you are assuming that any participants will be honest and forthcoming with responses or information they provide to you. Simply acknowledging this assumption as a possible limitation is important in your research.
• Access: Most research requires that you have access to people, documents, organizations, etc.. However, for various reasons, access is sometimes limited or denied altogether. If this is the case, you will want to acknowledge access as a limitation to your research.
• Time: Choosing a research focus that is narrow enough in scope to finish in a given time period is important. If such limitations of time prevent you from certain forms of research, access, or study designs, acknowledging this time restraint is important. Acknowledging such limitations is important, as they can point other researchers to areas that require future study.
• Potential Bias: All researchers have some biases, so when reading and revising your draft, pay special attention to the possibilities for bias in your own work. Such bias could be in the form you organized people, places, participants, or events. They might also exist in the method you selected or the interpretation of your results. Acknowledging such bias is an important part of the research process.
• Language Fluency: On occasion, researchers or research participants might have language fluency issues, which could potentially hinder results or how effectively you interpret results. If this is an issue in your research, make sure to acknowledge it in your limitations section.

University of Southern California (n.d.). Organizing your social sciences research paper: Limitations of the study . https://libguides.usc.edu/writingguide/limitations

In many research papers, the conclusion, like the limitations section, is folded into the larger discussion section. If you are unsure whether to include the conclusion as part of your discussion or as a separate section, be sure to defer to the assignment instructions or ask your instructor.

The conclusion is important, as it is specifically designed to highlight your research’s larger importance outside of the specific results of your study. Your conclusion section allows you to reiterate the main findings of your study, highlight their importance, and point out areas for future research. Based on the scope of your paper, your conclusion could be anywhere from one to three paragraphs long. An effective conclusion section should include the following:

• Describe the possibilities for continued research on your topic, including what might be improved, adapted, or added to ensure useful and informed future research.
• Provide a detailed account of the importance of your findings
• Reiterate why your problem is important, detail how your interpretation of results impacts the subfield of study, and what larger issues both within and outside of your field might be affected from such results

University of Southern California (n.d.). Organizing your social sciences research paper: 9. the conclusion . https://libguides.usc.edu/writingguide/conclusion

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• How to Write a Discussion Section | Tips & Examples

How to Write a Discussion Section | Tips & Examples

Published on 21 August 2022 by Shona McCombes . Revised on 25 October 2022.

The discussion section is where you delve into the meaning, importance, and relevance of your results .

It should focus on explaining and evaluating what you found, showing how it relates to your literature review , and making an argument in support of your overall conclusion . It should not be a second results section .

There are different ways to write this section, but you can focus your writing around these key elements:

• Summary: A brief recap of your key results
• Interpretations: What do your results mean?
• Implications: Why do your results matter?
• Limitations: What can’t your results tell us?
• Recommendations: Avenues for further studies or analyses

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Table of contents

What not to include in your discussion section, step 1: summarise your key findings, step 2: give your interpretations, step 3: discuss the implications, step 4: acknowledge the limitations, step 5: share your recommendations, discussion section example.

There are a few common mistakes to avoid when writing the discussion section of your paper.

• Don’t introduce new results: You should only discuss the data that you have already reported in your results section .
• Don’t make inflated claims: Avoid overinterpretation and speculation that isn’t directly supported by your data.
• Don’t undermine your research: The discussion of limitations should aim to strengthen your credibility, not emphasise weaknesses or failures.

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Start this section by reiterating your research problem  and concisely summarising your major findings. Don’t just repeat all the data you have already reported – aim for a clear statement of the overall result that directly answers your main  research question . This should be no more than one paragraph.

Many students struggle with the differences between a discussion section and a results section . The crux of the matter is that your results sections should present your results, and your discussion section should subjectively evaluate them. Try not to blend elements of these two sections, in order to keep your paper sharp.

• The results indicate that …
• The study demonstrates a correlation between …
• This analysis supports the theory that …
• The data suggest  that …

The meaning of your results may seem obvious to you, but it’s important to spell out their significance for your reader, showing exactly how they answer your research question.

The form of your interpretations will depend on the type of research, but some typical approaches to interpreting the data include:

• Identifying correlations , patterns, and relationships among the data
• Discussing whether the results met your expectations or supported your hypotheses
• Contextualising your findings within previous research and theory
• Explaining unexpected results and evaluating their significance
• Considering possible alternative explanations and making an argument for your position

You can organise your discussion around key themes, hypotheses, or research questions, following the same structure as your results section. Alternatively, you can also begin by highlighting the most significant or unexpected results.

• In line with the hypothesis …
• Contrary to the hypothesised association …
• The results contradict the claims of Smith (2007) that …
• The results might suggest that x . However, based on the findings of similar studies, a more plausible explanation is x .

As well as giving your own interpretations, make sure to relate your results back to the scholarly work that you surveyed in the literature review . The discussion should show how your findings fit with existing knowledge, what new insights they contribute, and what consequences they have for theory or practice.

Ask yourself these questions:

• Do your results support or challenge existing theories? If they support existing theories, what new information do they contribute? If they challenge existing theories, why do you think that is?
• Are there any practical implications?

Your overall aim is to show the reader exactly what your research has contributed, and why they should care.

• These results build on existing evidence of …
• The results do not fit with the theory that …
• The experiment provides a new insight into the relationship between …
• These results should be taken into account when considering how to …
• The data contribute a clearer understanding of …
• While previous research has focused on  x , these results demonstrate that y .

Even the best research has its limitations. Acknowledging these is important to demonstrate your credibility. Limitations aren’t about listing your errors, but about providing an accurate picture of what can and cannot be concluded from your study.

Limitations might be due to your overall research design, specific methodological choices , or unanticipated obstacles that emerged during your research process.

Here are a few common possibilities:

• If your sample size was small or limited to a specific group of people, explain how generalisability is limited.
• If you encountered problems when gathering or analysing data, explain how these influenced the results.
• If there are potential confounding variables that you were unable to control, acknowledge the effect these may have had.

After noting the limitations, you can reiterate why the results are nonetheless valid for the purpose of answering your research question.

• The generalisability of the results is limited by …
• The reliability of these data is impacted by …
• Due to the lack of data on x , the results cannot confirm …
• The methodological choices were constrained by …
• It is beyond the scope of this study to …

Based on the discussion of your results, you can make recommendations for practical implementation or further research. Sometimes, the recommendations are saved for the conclusion .

Suggestions for further research can lead directly from the limitations. Don’t just state that more studies should be done – give concrete ideas for how future work can build on areas that your own research was unable to address.

• Further research is needed to establish …
• Future studies should take into account …
• Avenues for future research include …

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Peer-reviewed

Research Article

Pharmacological and behavioral investigation of putative self-medicative plants in Budongo chimpanzee diets

Contributed equally to this work with: Elodie Freymann, Fabien Schultz

Roles Conceptualization, Data curation, Formal analysis, Funding acquisition, Investigation, Methodology, Project administration, Resources, Visualization, Writing – original draft, Writing – review & editing

* E-mail: [email protected] (EF); [email protected] (FS)

Affiliation Primate Models for Behavioural Evolution Lab, Institute of Human Sciences, Department of Anthropology and Museum Ethnography, University of Oxford, Oxford, United Kingdom

Roles Supervision, Writing – review & editing

Affiliations Primate Models for Behavioural Evolution Lab, Institute of Human Sciences, Department of Anthropology and Museum Ethnography, University of Oxford, Oxford, United Kingdom, Gorongosa National Park, Sofala, Mozambique, Interdisciplinary Centre for Archaeology and the Evolution of Human Behaviour, University of Algarve, Faro, Portugal

Roles Funding acquisition, Supervision, Writing – review & editing

Affiliations Ethnopharmacology & Zoopharmacognosy Research Group, Department of Agriculture and Food Sciences, Neubrandenburg University of Applied Sciences, Neubrandenburg, Germany, ZELT–Center for Nutrition and Food Technology gGmbH

Roles Formal analysis, Writing – original draft, Writing – review & editing

Affiliation Ethnopharmacology & Zoopharmacognosy Research Group, Department of Agriculture and Food Sciences, Neubrandenburg University of Applied Sciences, Neubrandenburg, Germany

Roles Resources, Supervision, Writing – review & editing

Affiliations Wild Minds Lab, School of Psychology and Neuroscience, University of St Andrews, St Andrews, United Kingdom, Budongo Conservation Field Station, Masindi, Uganda

Affiliation Wildlife Research Center, Inuyama Campus, Kyoto University, Inuyama, Japan

Roles Investigation

Affiliation Budongo Conservation Field Station, Masindi, Uganda

Roles Formal analysis

Affiliations Budongo Conservation Field Station, Masindi, Uganda, Czech University of Life Sciences Prague, Prague, Czech Republic

Roles Resources, Writing – review & editing

Affiliations Budongo Conservation Field Station, Masindi, Uganda, Department of Comparative Cognition, Institute of Biology, University of Neuchâtel, Neuchâtel, Switzerland

Roles Conceptualization, Data curation, Formal analysis, Funding acquisition, Investigation, Methodology, Project administration, Resources, Writing – original draft, Writing – review & editing

Affiliations Ethnopharmacology & Zoopharmacognosy Research Group, Department of Agriculture and Food Sciences, Neubrandenburg University of Applied Sciences, Neubrandenburg, Germany, Pharmacognosy and Phytotherapy, School of Pharmacy, University College of London, London, United Kingdom

• Elodie Freymann, 
• Susana Carvalho, 
• Leif A. Garbe, 
• Dinda Dwi Ghazhelia, 
• Catherine Hobaiter, 
• Michael A. Huffman, 
• Geresomu Muhumuza, 
• Lena Schulz, 
• Daniel Sempebwa, 

• Published: June 20, 2024
• https://doi.org/10.1371/journal.pone.0305219
• Reader Comments

Wild chimpanzees consume a variety of plants to meet their dietary needs and maintain wellbeing. While some plants have obvious value, others are nutritionally poor and/or contain bioactive toxins which make ingestion costly. In some cases, these nutrient-poor resources are speculated to be medicinal, thought to help individuals combat illness. In this study, we observed two habituated chimpanzee communities living in the Budongo Forest, Uganda, and collected 17 botanical samples associated with putative self-medication behaviors (e.g., bark feeding, dead wood eating, and pith-stripping) or events (e.g., when consumer had elevated parasite load, abnormal urinalysis, or injury). In total, we selected plant parts from 13 species (nine trees and four herbaceous plants). Three extracts of different polarities were produced from each sample using n -hexane, ethyl acetate, and methanol/water (9/1, v/v ) and introduced to antibacterial and anti-inflammatory in vitro models. Extracts were evaluated for growth inhibition against a panel of multidrug-resistant clinical isolates of bacteria, including ESKAPE strains and cyclooxygenase-2 (COX-2) inhibition activity. Pharmacological results suggest that Budongo chimpanzees consume several species with potent medicinal properties. In the antibacterial library screen, 45 out of 53 extracts (88%) exhibited ≥40% inhibition at a concentration of 256 μg/mL. Of these active extracts, 41 (91%) showed activity at ≤256μg/mL in subsequent dose-response antibacterial experiments. The strongest antibacterial activity was achieved by the n- hexane extract of Alstonia boonei dead wood against Staphylococcus aureus (IC50: 16 μg/mL; MIC: 32 μg/mL) and Enterococcus faecium (IC50: 16 μg/mL; MIC: >256 μg/mL) and by the methanol-water extract of Khaya anthotheca bark and resin against E . faecium (IC50: 16 μg/mL; MIC: 32 μg/mL) and pathogenic Escherichia coli (IC50: 16 μg/mL; MIC: 256 μg/mL). We observed ingestion of both these species by highly parasitized individuals. K . anthotheca bark and resin were also targeted by individuals with indicators of infection and injuries. All plant species negatively affected growth of E . coli . In the anti-inflammatory COX-2 inhibition library screen, 17 out of 51 tested extracts (33%) showed ≥50% COX-2 inhibition at a concentration of 5 μg/mL. Several extracts also exhibited anti-inflammatory effects in COX-2 dose-response experiments. The K . anthotheca bark and resin methanol-water extract showed the most potent effects (IC50: 0.55 μg/mL), followed by the fern Christella parasitica methanol-water extract (IC50: 0.81 μg/mL). This fern species was consumed by an injured individual, a feeding behavior documented only once before in this population. These results, integrated with associated observations from eight months of behavioral data, provide further evidence for the presence of self-medicative resources in wild chimpanzee diets. This study addresses the challenge of distinguishing preventative medicinal food consumption from therapeutic self-medication by integrating pharmacological, observational, and health monitoring data—an essential interdisciplinary approach for advancing the field of zoopharmacognosy.

Citation: Freymann E, Carvalho S, Garbe LA, Dwi Ghazhelia D, Hobaiter C, Huffman MA, et al. (2024) Pharmacological and behavioral investigation of putative self-medicative plants in Budongo chimpanzee diets. PLoS ONE 19(6): e0305219. https://doi.org/10.1371/journal.pone.0305219

Editor: Armel Jackson Seukep, University of Buea, CAMEROON

Received: January 9, 2024; Accepted: May 25, 2024; Published: June 20, 2024

Copyright: © 2024 Freymann et al. This is an open access article distributed under the terms of the Creative Commons Attribution License , which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Data Availability: All relevant data are within the manuscript and its Supporting Information files.

Funding: Funding for this project was granted by the the Clarendon Fund at the University of Oxford (to EF), the British Institute of Eastern Africa (to EF), Keble College at the University of Oxford (to EF), Boise Trust Fund (to EF), German Federal Ministry of Education and Research (13FH026IX5, PI: L-AG and Co-I: FS) (to LAG, FS) and Neubrandenburg University of Applied Sciences (grant # 13310510) (to LAG, FS).

Competing interests: The authors have declared that no competing interests exist.

Introduction

‘Medicinal foods’ refer to resources in the diet that have potential curative value due to the presence of plant secondary metabolites (PSMs) [ 1 , 2 ]. PSMs are compounds that usually occur only in special, differentiated cells [ 3 ] and which help plants defend against predators, pathogens, and competitors [ 4 – 7 ]. PSMs can have a range of functions, including the inhibition of microbial, fungal, and competitor growth [ 8 ]. While some PSMs can be toxic at high doses, these compounds can also promote the health of human and non-human consumers [ 8 – 10 ]. Research suggests 15–25% of primate and other mammalian diets consist of medicinal foods [ 9 , 11 ]. These resources likely play a critical role in animal health-maintenance by passively preventing or reducing the impact of parasitic infections or other pathogens [ 9 – 14 ].

While most animals likely consume foods with medicinal properties as part of their normal diets, fewer species have been shown to engage in therapeutic self-medication. Huffman [ 15 ] defines this type of self-medicative behavior as the active extraction and ingestion, by an ill individual, of medicinal resources with little nutritional value. Instead of an individual passively benefiting from a plant’s medicinal properties through normal feeding, this form of self-medication requires basic awareness of the resource’s healing properties. One of the best-studied animals to engage in this form of self-medication is our closest living relative: the chimpanzee.

Wild chimpanzees ( Pan troglodytes ), across at least sixteen field sites [ 15 ] have demonstrated therapeutic self-medication using two well-established self-medicative behaviors: leaf swallowing [ 16 , 17 ] and bitter-pith chewing [ 18 ]. Leaf swallowing, first reported by Wrangham [ 19 , 20 ] and described by Wrangham & Nishida [ 21 ], involves the careful selection and ingestion of whole, hispid leaves. This behavior was later demonstrated to expel internal parasites (i.e. Oesophagostomum sp. and Bertiella studeri ) from the gut [ 16 , 17 , 22 , 23 ]. The functional mechanism responsible for this anthelminthic effect is considered to be primarily “mechanical” [ 9 ] as, rather than a chemical compound, the leaf’s indigestibility, brought about by the trichomes on its surface—stimulates gut motility in the swallower [ 17 , 23 , 24 ].

The second established behavior is bitter-pith chewing, which involves the stripping of outer bark and leaves from the soft new stem growth of the shrub, Vernonia amygdalina , exposing the inner pith. Individuals chew the pith and ingest only the bitter juices while spitting out the fibers [ 18 , 25 ]. Bitter-pith chewing is considered ‘phytochemical’ self-medication [ 9 ], as its anthelminthic effect appears to be the result of bioactive PSMs [ 26 – 29 ]. This behavior’s medicinal effect was associated with a significant drop in the infection intensity of Oesophagostomum stephanostomum nematodes [ 25 ], suggesting that the bitter compounds directly affect the adult worms. This hypothesis was supported by in vivo studies conducted by Jisaka et al. [ 30 ], demonstrating that extracts from the pith permanently paralyzed adult Schistosome parasites. V . amygdalina is also used to aid gastrointestinal discomfort and other signs of parasitosis in humans and livestock, symptoms also displayed by chimpanzees ingesting the plant’s bitter pith [ 9 , 18 , 25 , 31 ]. The bitter piths of other plant species are reported to be chewed by chimpanzees across field sites but detailed studies on their medicinal properties have yet to be conducted [ 9 ].

Beyond these two established behaviors, not much is known about the phytochemical self-medicative repertoires of wild chimpanzees, although some behaviors associated with the ingestion of specific plant parts or processing techniques have been recommended for further investigation [ 9 , 15 , 32 ]. One of these behaviors is bark feeding, which involves the ingestion of living stem bark and/or cambium [ 33 ], and which has been observed in at least eleven established field sites [ 33 – 43 ]. Bark feeding has been suggested as a medicinal behavior in chimpanzees and other primates, used to aid in the chemical control of intestinal nematode infection and to relieve gastrointestinal upset [ 9 ]. Bark is characteristically highly fibrous, heavily lignified, sometimes toxic, relatively indigestible, and nutrient-poor [ 44 ]. However, the contribution of bark in chimpanzee diets and toward general health is still poorly understood [though see: 45 ]. In this study, the bark of eight species ingested by Budongo chimpanzees ( Scutia myrtina , Cynometra alexandri , Alstonia boonei , Ficus exasperata , Ficus variifolia , Syzygium guineense , Desplatsia dewevrei , Khaya anthotheca) was screened for antibiotic and anti-inflammatory properties, to better understand the function of bark feeding behaviors and the role this behavior may play in the health maintenance of chimpanzees. For the species K . anthotheca , we tested a mixture of bark and congealed resin, which Budongo chimpanzees were observed to particularly target throughout the study period.

Another putative self-medicative behavior is dead wood eating [ 9 , 35 ], which involves the consumption of decomposing cambium from dead trees. To date, the majority of studies examining this behavior in apes have focused on exploring potential mineral and nutritional benefits, rather than investigating pharmacological properties [ 46 – 49 ]. Many of these studies suggest that dead wood is exploited by chimpanzees as a source of sodium in environments where this mineral is otherwise scarce [ 48 , 49 ]. Our study evaluates the pharmacology of two species of dead wood ( A . boonei and Cleistopholis patens) consumed by the Sonso community of chimpanzees to determine whether this behavior may have multiple functions or health benefits.

The ingestion of pith material from other species has also been suggested as putatively self-medicative [ 34 , 50 , 51 ]. However, unlike V . amygdalina bitter-pith, some of these plant piths appear bland or tasteless. While Wrangham et al. have previously suggested that pith is likely a high-fiber fallback food [ 52 ], De la Fuente et al. review several pith species targeted by chimpanzees with proposed medicinal properties [ 32 ]. In our study, two species of non-bitter piths ( Marantachloa leucantha and Acanthus polystachyus) , were collected for pharmacological assessment. M . leucantha was observed on several occasions being stripped, masticated, and spat out after the juice was extracted from the pith, whereas A . polystachyus was observed being stripped, masticated, and swallowed. Both of these species are also ingested by chimpanzees in Kibale National Park, Uganda [ 52 ].

Establishing phytochemical self-medicative behaviors in wild animals is difficult and time consuming, as the burden of proof is high, self-medicative events can be rare relative to other behaviors, and methods often require multidisciplinary expertise and collaboration [ 9 ]. Past studies have utilized ethnopharmacological methods to determine specific medicinal properties of foods consumed by primates [ 11 ], greatly advancing our understanding of the relationship between primate diets and health. However, a key challenge for establishing novel self-medicative behaviors is differentiating between medicinal food consumption and therapeutic self-medication. While pharmacological data interpreted on its own is crucial for establishing the presence of medicinal resources in chimpanzee diets, the integration of observational and health monitoring data is needed to parse therapeutic self-medicative behaviors from normal feeding behaviors with inadvertent health benefits. Furthermore, the importance of collecting in situ samples from the locations where putative self-medicative behaviors are observed is paramount, as ecological, climatic, and anthropogenic variables can cause variation in the bioactivity of plants across habitats [ 53 ].

In total, we investigated the bioactivity of 51 plant extracts produced from 17 part-specific samples (across 13 species), collected in the Budongo Forest. Each extract was tested for inhibition of bacterial growth as well as anti-inflammatory COX-2 inhibition activity. Due to limitations in scope, funding, and the unavailability of anthelminthic assays for wild animal parasites, none were not conducted in this study, restricting specific identification of parasiticidal behaviors. Assay results are reported and contextualized in this study with direct behavioral evidence and health monitoring data.

Materials and method

Study site and subjects.

Behavioral data, health monitoring metrics, and botanical samples were collected from the Budongo Central Forest Reserve in Uganda (1°35′– 1°55′ N, 31°18′–31°42′ E). An overview of methodological workflow can be found in S2 Fig . The Budongo Conservation Field Station (BCFS) site, founded in 1990, is composed of continuous, semi-deciduous forest and contains two habituated Eastern chimpanzee ( Pan troglodytes schweinfurthii ) communities [ 54 ]. The Sonso community has been studied continuously since 1992, and the ages, social relationships, demographics, and diet of its members are well documented [ 55 , 56 ]. The Sonso population was ~68 individuals at the time of data collection, and the home range covered an area of ~5.33 km 2 [ 57 ]. Waibira, a larger group of at least 105 individuals, was more recently habituated, with consistent data collection beginning in 2011. The Waibira maximum home range area was ~10.28 km 2 [ 57 ].

Behavioral data collection

All samples were collected in the Budongo Forest within the Sonso home range, based on behavioral observations from the study period and supporting evidence from the site’s long-term data of their use. Behavioral and health data were collected from two neighboring chimpanzee communities, each for one four-month field season (Sonso: June-October 2021, Waibira: June-October 2022). Data collected between June-September 2021 informed subsequent plant sample collection for pharmacological analysis, which occurred in early September 2021. Behavioral data collected after sample collection provided additional behavioral context for ingestion of these species. Behavioral data were collected between 07:00 and 16:30 in Sonso and between 06:30 and 17:00 in Waibira using day-long focal animal follows sensu Altman et al. [ 58 ]. This data was recorded using Animal Observer (AO) on iPad and ad libitum feeding events were recorded for any unusual feeding behaviors, including but not limited to bark ingestion, dead wood eating, pith stripping, and geophagy. All feeding events were filmed on a Sony Handycam CX250. We prioritized focal follows on individuals with wounds, high or diverse parasite loads identified through on-going monitoring, or known ailments. However, consecutive day follows of priority individuals were not always possible—or were avoided when they might contribute to increased stress in particularly vulnerable individuals. Throughout the study, using this protocol, 27 Sonso individuals (♂:11; ♀:16) and 24 Waibira individuals (♂:14; ♀:10) were observed. Authors collecting behavioral data were blind to pharmacological results during both study periods.

Health monitoring

Individual health data were recorded in both communities, including opportunistic macroscopic and microscopic fecal analysis and urinalysis testing. While anthelminthic assays were not run in this study, parasite load was opportunistically assessed to provide additional health context for each observation. As the presence of certain helminths may impair a host’s immunological response to bacterial, viral, and protozoal pathogens [ 59 ], parasite load can provide a proxy measurement for overall health. Similarly, a reduced immune system and increased stress caused by co-infections could render a host more susceptible to virulent endoparasites [ 60 , 61 ]. When helminths and/or proglottids were found in samples, they were collected and preserved in ethanol for later identification. To quantify parasite loads, fecal samples were analyzed using the McMaster Method [ 9 , 25 , 62 ]. Urinalysis samples were taken opportunistically using multi-reagent Urine Dipstick Test 9-RC for Urotron RL9 to assess the health and physiological status of group members following methods established by Kaur & Huffman [ 63 ]. Urinalysis metrics considered in this study included: leukocytes (LEU) associated with pyuria caused by UTI, balanitis, urethritis, tuberculosis, bladder tumors, viral infections, nephrolithiasis, foreign bodies, exercise, glomerulonephritis, and corticosteroid and cyclophosphamide use; blood (BLO) associated with peroxidase activity of erythrocytes, and UTIs; and ketones (KET) associated with pregnancy, carbohydrate-free diets, starvation, and diabetes [ 64 ]. Test results were interpreted in situ using a colorimetric scale. We considered a result ‘abnormal’ if the colorimetric scale indicated a positive result when the expected result was negative or if the result was outside the specified test parameters according to the manufacturer.

Plant sample selection for bioactivity testing

Plants were selected for pharmacological testing after three months of data collection in the Sonso community. We selected 10 samples (from 9 species) based on direct observations during this period. These observations included individuals targeting plant parts associated with putative self-medicative behaviors (i.e., bark feeding, dead wood eating, pith-stripping) or sick/wounded individuals seeking out unusually consumed resources. We then selected an additional five species, the ingestion of which had not been directly observed, for testing based on their historical inclusion in Sonso chimpanzees’ bark feeding repertoire. GM, who has worked at the field station for over thirty-years, has previously observed bark feeding on each of these selected species. These historic observations enabled collection of bark samples from specific trees known to have been previously stripped. In two cases, leaf samples were collected from tree species that were also selected for bark samples ( S . guineense and F . exasperata) . While neither Sonso nor Waibira chimpanzees have been observed ingesting the leaves of S . guineense , a sample was collected to enable comparison of bioactivity across plant parts. F . exasperata leaves are consumed in both communities; however, we found no behavioral evidence for use in unusual contexts. In some cases, direct observation of an event involving one of the collected species occurred after botanical collection was complete. These post hoc behavioral observations are reported in this paper, although they did not impact sample selection.

Collection of sample material

Plants were collected from the Sonso community home range following best practice procedures [ 65 ], using sustainable harvesting methods [ 66 ]. See S1 File for more information. Voucher accession numbers are reported in Table 3 . Digital images of voucher specimens can be found in S3 Fig . The currently recognized scientific names of each species were confirmed on https://mpns.science.kew.org/ . Plant family assignments were done in accordance with The Angiosperm Phylogeny Group IV guidance [ 67 ].

Ethnobotanical literature review

We conducted a post-hoc ethnomedicinal review of all species collected for this study using Google Scholar, PROTA, and Kokwaro’s ethnomedicinal pharmacopeia [ 68 ]. To search databases, we used scientific names and synonyms for each plant as keywords [ 65 ].

Plant processing and extractions

At Neubrandenburg University of Applied Sciences, samples were ground using a food processor. Extractions were produced using two solvents and a solvent mixture ( n -hexane, ethyl acetate, and methanol/water ( v/v 9/1)), allowing for the selective isolation of components with varying solubilities and polarities. Methanol-water, the solvent with the highest polarity, generally extracts primary plant metabolites (e.g., polar compounds such as proteins, amino acids, and carbohydrates). Nonpolar solvents like n- hexane extract nonpolar compounds like lipids, making n-hexane a preferred solvent for oil or wax extraction. Extractions with each solvent were achieved through double maceration of new material (non-successively). Extraction suspensions were placed on a shaker at 80 rpm at room temperature for minimum 72h, followed by vacuum filtration. Processes were repeated with the leached material. Filtrates were then combined and dried using a vacuum evaporator, labeled, and stored at -20°C until needed for assays.

Sample solution preparation

To create sample solutions, each crude extract was dissolved in DMSO (Carl Roth) at a concentration of 10 mg/mL. To ensure a homogenous solution, samples were mixed with a vortex mixer and, if necessary, treated with sonication at room temperature or up to 55°C for samples with low solubility. Each extract solution was then tested for inhibition of bacterial growth as well as anti-inflammatory COX-2 inhibition activity. Solutions were stored at -20°C when not in use.

Antibacterial susceptibility tests

A. bacterial strains..

For antibacterial assays, eleven multidrug-resistant clinical isolate strains from nine species were used. This process increased the study’s applicability for early-stage drug discovery, specifically relevant to the threat of antimicrobial resistance (AMR). Seven of these strains (from six species) are classified as ESKAPE pathogens, including Enterococcus faecium (DSM 13590), Staphylococcus aureus (DSM 1104; DSM 18827), Klebsiella pneumoniae (DSM 16609), Acinetobacter baumannii (DSM 102929), Pseudomonas aeruginosa (DSM 1117), and Enterobacter cloacae (DSM 30054), meaning they are highly virulent and resistant to antibiotics [ 69 ]. A strain of the foodborne pathogen Escherichia coli (DSM 498) with AMR as well as a non-resistant E . coli strain (DSM 1576) were also included in the study. Although not an ESKAPE pathogen, E . coli is widely known for causing bacterial diarrhea and AMR strains are a major cause of urinary tract infections [ 70 , 71 ]. Strains of Stenotrophomonas maltophilia (DSM 50170) and Salmonella enterica subsp. enterica (DSM 11320) were also tested. More information on specific clinical isolates/strains, their individual resistance profiles, and antibiotics used can be found in the S5 & S6 Tables in S2 File . Clinical and Laboratory Standards Institute (CLSI) guidelines for broth microdilution testing (M100-S23) were followed [ 72 ].

b. Growth inhibition screening and dose-response study.

The broth dilution in vitro methods for bacterial susceptibility assessment have previously been described by Schultz et al. [ 69 ]. The standardized bacterial working cultures were pipetted into sterile 96-well microtiter plates (Greiner Bio-One International, CELLSTAR 655185). Extracts and antibiotic (64–1 μg/mL), vehicle and sterility controls, were then added into respective wells. Initial optical density measurement (600 nm) was performed, accounting for absorbance of extracts. Plates were incubated at 37°C for 18 h, except for A . baumannii which was incubated for 22h in accordance with strain characteristics ( S5 Table in S2 File ) . After incubation, a final optical density reading (600 nm) was conducted. Percent inhibition values were calculated and the IC 50 and MIC values were determined [ 69 , 73 ]. The IC 50 value is defined as the lowest concentration at which an extract showed ≥ 50% inhibition, and the MIC is the lowest concentration at which an extract displayed ≥ 90% inhibition. A total of 51 samples underwent single-dose pre-screening for growth inhibition (in triplicate) at the concentration of 256 μg/mL on eleven pathogens. Samples showing ≥40% growth inhibition were further tested in a dose-response study with two-fold serial dilution at descending concentrations from 256 to 4 μg/mL. The dose-response experiments were done as biological replicates on separate days in triplicate (technical replicates) to validate reproducibility. Positive controls (antibiotics) and negative controls (vehicle control and sterile media control) were always included. Further details on bacteria standardization can be found in S1 File . Information on plate setup for bacterial library screens and dose-response assays can be found in S4 Fig .

COX-2 inhibition assay

Anti-inflammatory assays were assessed using an in vitro COX inhibitor screening assay kit (Cayman Item No: 701080), with modifications previously described in Schultz et al. [ 74 ]. All extracts were first screened in duplicate for inhibition against human recombinant COX-2 at an initial concentration of 50 μg/mL. For extracts exhibiting at least 50% inhibition, the concentration was then lowered to 10 μg/mL, 5 μg/mL, and 2.5 μg/mL. The most active extracts were taken to dose-response experiments for determination of IC 50 values ( Table 5 ). The assay was done in two steps: 1) the COX reaction step in which the prostaglandin H 2 (PG) was produced (which was further reduced to the more stable prostaglandin F 2α by addition of stannous chloride), and 2) an acetyl choline esterase competitive ELISA step to quantify the produced prostaglandin and calculate a potential enzyme inhibition caused by the extracts. The pure compound and selective COX-2 inhibitor DuP-769 was included as a positive control. DMSO was included as the vehicle control for determining 100% enzyme activity. Information on ELISA plate setup for anti-inflammation assays can be found in S5 Fig .

Ethics statements

Behavioral data used in this study were collected with the approval of the Uganda Wildlife Authority (permit #: COD/96/05) and the Uganda National Council for Science and Technology (permit #: NS257ES). Exportation of samples for pharmacological testing were conducted under UNCST permit #: NS104ES. Behavioral data collection adhered to International Primatological Society’s Code of Best Practice for Field Primatology [ 75 ]. No exported samples were listed under CITES. Plant samples were exported in collaboration with Makerere University (permit #: UQIS00005033/93/PC), issued by the Ugandan government, and transported to Neubrandenburg University of Applied Sciences in accordance with the Nagoya Protocol. A CUREC was approved by the University of Oxford (Ref No.: SAME_C1A_22_080). The authors report no conflict of interest.

Behavioral observations

Several unusual feeding events and putative self-medicative behaviors were recorded over 116 total field days. Table 1 reports all species collected for pharmacological testing and provides behavioral justifications for collection. Images from some of these events can be found in S1 Fig .

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https://doi.org/10.1371/journal.pone.0305219.t001

Individuals with injuries were directly observed ingesting K . anthotheca bark and resin, W . elongata young leaves, C . alexandri bark, and C . parasitica ferns. Individuals exhibiting respiratory symptoms were observed ingesting C . alexandri bark and K . anthotheca bark and resin. Individuals with abnormal urinalysis results (e.g., positive for leukocytes, elevated ketones, and presence of blood) were observed feeding on C . patens dead wood, K . anthotheca bark and resin, and M . leucantha pith. Individuals with recent cases of diarrhea were observed consuming A . boonei and C . patens dead wood, K . anthotheca bark and resin, and W . elongata leaves. Parasitological analyses further suggest individuals with varying degrees of endoparasite infections consumed S . myrtina and C . alexanderi bark, A . boonei and C . patens dead wood, K . anthotheca bark and resin, W . elongata leaves, as well as A . polystachyus and M . leucantha pith. On a day when two individuals were observed leaf swallowing, a scientifically established self-medicative behavior, one was observed consuming K . anthotheca bark and resin, while the other was observed stripping A . polystachyus pith prior to the event. Ingestion of F . variifolia , D . dewevrei , and S . guineense bark were never directly observed during the study period. Examples of bark feeding, dead wood eating, and pith-stripping marks are shown in Fig 1 .

[ a ]: Evidence of F. exasperata bark feeding [ b ] Evidence of C. patens dead wood eating [ c ] Evidence M. leucantha pith-stripping and wadging.

https://doi.org/10.1371/journal.pone.0305219.g001

Ethnobotanical review

Based on our analysis of ethnomedicinal literature spanning various African regions from 1976 to 2022, 11 out of the 13 species tested also had documented ethnomedicinal uses ( Table 2 ).

https://doi.org/10.1371/journal.pone.0305219.t002

Production of extracts and sample information

Taxonomic information and extraction details for the 13 plant species studied, including the plant family, local name (when available), plant part used, solvent for extraction, yield of extraction, extract identification numbers (extract IDs), herbarium accession numbers, and collection location are summarized in Table 3 . Overall, the highest extraction yields were obtained with methanol-water (9/1) as a solvent. The yields from methanol-water extractions for C . parasitica , F . exasperata leaves, and S . guineense stem bark were higher than the other extractions from these samples. The plant samples which had higher yield values with n -hexane, such as the leaves of W . elongata and bark extract of A . boonei , likely have a higher content of lipids (i.e., fatty molecules).

https://doi.org/10.1371/journal.pone.0305219.t003

Library screening against multidrug-resistant human and food bacterial pathogens

Initial screening of extracts involved checking for growth inhibition against each bacterium at a concentration of 256 μg/mL. In total, 45 of the 51 plant extracts (88%) showed activity ≥40% inhibition against at least one of the 11 strains and were thus considered active and brought to dose-response experiments to determine their IC 50 value and MIC. Results from the library screening are reported in S1 Table in S2 File . As all tested plant species in the library screen had at least one extract that was active ( in vitro ) against at least one bacterial strain, no entire species was eliminated for further experimentation. However, as no extracts (at any concentration) inhibited the growth of K . pneumoniae , no further tests were conducted on this bacterium. The extract active against the most bacterial strains (n = 11) was the methanol-water extract of S . guineense stem bark (mwE098a, active against eight strains), followed by the methanol-water S . guineense leaves (mwE098b), the ethyl acetate P . patens dead wood, and the n -hexane A . boonei dead wood (hE092b) extracts, which were each active against seven, seven, and six strains, respectively. The only extract that demonstrated significant inhibition against P . aeruginosa at the highest test concentration was the methanol-water extract from S . guineense bark (mwE098a). This was also the only extract to display significant inhibition at 256 μg/mL against E . cloacae . Of all bacteria in this study, the two strains of E . coli (DSM 498 and DSM 15076) were the most susceptible, with at least one extract from all plant species inhibiting their growth. The E . coli strain with nine known antibiotic resistances (DSM 15076) surprisingly showed growth inhibition in 80% of tested extracts.

Dose-response antibacterial experiments

In dose-response assays, 41 out of the 45 tested extracts (91%) showed activity at ≤256μg/mL, though not all extracts reached MIC values (see Table 4 ). The results, along with standard deviations, are reported in S2 Table in S2 File , while S3 Table in S2 File provides a summary of the number of strains each extract was active against. The strongest in vitro growth inhibition was reported for the methanol-water extract of K . anthotheca bark and resin (mwE088) against Gram-positive E . faecium and the n- hexane extract of A . boonei dead wood (hE092b) against Gram-positive S . aureus (DSM 1104). Both extracts had low IC 50 values of 16 μg/mL (showing strong inhibition), with MIC values of 32 μg/mL against respective strains. E . faecium showed the most general susceptibility to K . anthotheca , with all extracts of this species achieving MIC values (mwE088: 32 μg/mL, eE088: 64 μg/mL, hE088: 128 μg/mL). The ethyl acetate extract of A . boonei dead wood (eE092b) also strongly inhibited the growth of E . faecium (IC 50 : 16 μg/mL; MIC: 64 μg/mL), as did the n- hexane extract of A . boonei dead wood, producing an IC 50 value of 16 μg/mL but failing to reach a MIC value. S . aureus (DSM 1104) was also highly susceptible to the ethyl acetate extracts of A . boonei dead wood (IC 50 : 32 μg/mL; MIC: 128 μg/mL).

https://doi.org/10.1371/journal.pone.0305219.t004

Only one extract, the methanol-water extract of S . guineense bark (mwE098a), was active against the gram-negative P . aeruginosa . This extract exhibited moderate growth inhibition (IC 50 : 64 μg/mL) with no MIC value reached. Despite E . coli (DSM 498) being highly susceptible on the library screen, only two extracts, the methanol-water extract of A . boonei dead wood (mwE092b; IC 50 : 256 μg/mL) and the methanol-water extract of S . guineense leaves (mwE098b; IC 50 : 128 μg/mL), reached IC 50 values at the concentration range tested, with no MICs reached. Interestingly, the strain of E . coli with nine known resistances (DSM 1576) was more susceptible, with 89% (N = 40) of extracts achieving IC 50 values ≤ 256 μg/mL. The most active extract against this strain was the methanol-water extract of K . anthotheca (mwE088; IC 50 : 16 μg/mL; MIC: 256 μg/mL). S . guineense exhibited the highest overall inhibition of S . maltophilia , with all extracts except hE098a displaying IC 50 values of ≤ 256 μg/mL against the bacterium. At the concentration range tested, no extracts yielded MIC values for S . aureus (DSM 18827), A . baumannii , E . cloacae , P . aeruginosa or E . coli (DSM 498).

Anti-inflammatory COX-2 inhibition library screen

Results from the in vitro COX-2 inhibition library screen at descending concentrations are reported in S4 Table in S2 File . At the initial concentration of 50 μg/mL, 43 out of 51 extracts (84%) exhibited an enzyme inhibition of at least 50%, displaying anti-inflammatory activity. This included at least one extract of every plant species. In the next stage of screening, at 10 μg/mL, 18 samples were eliminated. During the final step, at 5 μg/mL, five more were eliminated. The remaining 17 extracts from 10 plant species which displayed inhibition ≥50% at 5 μg/mL, were then introduced to dose-response experiments. The ethyl acetate S . myrtina bark extract (eE089b) was taken to the COX-2 dose-response despite not showing inhibition past 50 μg/mL, as it almost reached the selection limit during analysis and had a relatively high standard deviation. No extracts from W . elongata , C . patens or D . dewevrei showed COX-2 inhibition at 5 μg/mL and thus were excluded from further testing.

COX-2 inhibition dose-response experiments

The most active COX-2 inhibitors were extracts from K . anthotheca (mwE088; hE088; eE088), C . parasitica (mwE087; hE087), F . exasperata (hE093a; eE093a), S . myrtina (hE089a; eE089b), F . variifolia (eE097; hE097), A . polystachyus (hE099; eE099), M . leucantha (hE094), S . guineense (hE098a), A . boonei (hE092b), and C . alexandri (hE096). Results are reported in Table 5 . The strongest COX-2 inhibitor was the K . anthotheca methanol-water bark and resin extract (mwE088) (IC 50 of 0.55 μg/mL), followed by the C . parasitica methanol-water fern extract (mwE087) (IC 50 of 0.81 μg/mL). In contrast, all extracts of the species W . elongata , C . patens , and D . dewevrei failed to show ≥50% inhibition, mostly at the second screening concentration (10 μg/mL). W . elongata extracts notably showed low activity in both antibacterial and COX-2 inhibition assays.

https://doi.org/10.1371/journal.pone.0305219.t005

Plant species with strong pharmacological activity

This study provides the first pharmacological and behavioral evidence of its kind, based on in situ sampling, for the medicinal benefits of bark feeding, dead wood eating, and non-bitter pith stripping behaviors in Budongo chimpanzees. In the following sub-sections, we describe and discuss specific results from five of the tested plant species in further detail. For scope, we selected the two species with the strongest antibacterial properties ( K . anthotheca and A . boonei ) to profile, both of which were the only species to reach 40% inhibition at 16 μg/mL. We also selected C . parasitica to discuss as this species, along with K . anthotheca , exhibited the strongest anti-inflammatory properties. We then discuss results from our S . guineense samples, as this species was effective against the most bacterial strains in our antibacterial assays. Lastly, we selected S . myrtina , as we have behavioral evidence and health data that anecdotally support the use of this species for therapeutic self-medication by Budongo chimpanzees.

Alstonia boonei . Numerous in vitro and in vivo studies, reviewed by Adotey [ 76 ], have reported pharmacological activity in A . boonei bark. However, none of these studies investigated dead wood samples of A . boonei . Consistent with these findings, we found high levels of antibacterial and anti-inflammatory activity in the extracts of this species. Interestingly, extracts from A . boonei dead wood generally exhibited higher activity than living bark. This difference could be due either to a change in active ingredient composition, or possible fungal growth following the tree’s death. While the A . boonei dead wood n -hexane extract (hE092b) exhibited strong growth inhibition against S . aureus (DSM 1104; DSM 18827) and E . faecium at low concentrations in the dose-response assays, the n -hexane bark extract (hE092a) showed no activity <256 μg/mL. Similarly, the ethyl acetate extract of dead wood (eE092b) also strongly inhibited S . aureus (DSM 1104) (IC 50 : 16 μg/mL; MIC: 128 μg/mL) and E . faecium (IC 50 : 16 μg/mL; MIC: 64 μg/mL), while the ethyl acetate bark extract of this species did not even exhibit enough inhibition in the antibacterial library screen to be taken to dose-response assays. However, the methanol-water extract of A . boonei bark (mwE092a) did show activity against E . coli (DSM 498) (IC 50 : 128 μg/mL), as did the methanol-water dead wood extract (mwE092a) (IC 50 : 128 μg/mL), with no MIC values reached in either case. Overall, extracts from A . boonei displayed more potent activity in Gram-positive bacteria, although this effect is more apparent in dead wood than stem bark. In the COX-2 inhibition assays, the n -hexane extract of A . boonei dead wood also showed strong anti-inflammatory inhibition, while the n -hexane extract of the bark only exhibited weak inhibition (at the highest test concentration of 50 μg/mL).

A . boonei is a known medicinal plant across East Africa, commonly used for a variety of reproductive, bacterial, and gastro-intestinal issues, as well as for snake bites, asthma, and dizziness [ 68 , 76 , 77 ]. The bark and latex are intensely bitter, a reliable signal of the presence of bioactive secondary compounds and toxicity [ 94 – 96 ]. Budongo chimpanzees in both communities have been reported to consume both bark and dead wood of A . boonei , often travelling long distances to access these trees and only consuming small amounts of bark per feeding bout [ 45 ]. In an observation reported in this study (see Table 1 : A . boonei , Case 1 ), three males ingested A . boonei dead wood while outside the community’s core area for 1-minute. Two days before the event, one of the individuals had been observed with diarrhea, while also shedding visible tapeworm proglottids ( Bertiella sp.). This sample also contained unidentified protozoa, and Taenia sp. eggs. Pebsworth et al. [ 34 ] also reported an event in which four adult males, all with diverse parasite loads, traveled to a large A . boonei tree and ingested bark.

In the long-term site data, A . boonei bark ingestion was only documented 17 times between 2008–2021 [ 45 ], although this behavior was not systematically reported. In addition, the direct observation of only one A . boonei dead wood eating event, and no A . boonei bark ingesting events over the two four-month periods of observation in this study, suggest that consumption of this species is relatively rare across both communities. While specific pathogenic catalysts for selection of this species remain unknown, based on pharmacological, ethnobotanical, and behavioral data, we propose that A . boonei may be a therapeutic self-medicative resource for Budongo chimpanzees. The relatively strong inhibitory activity of this species against S . aureus , a bacteria associated with causing contamination on the skin leading to chronic wounds [ 97 ], as well as its anti-inflammatory properties, suggests that A . boonei ingestion may have beneficial effects in wound care contexts.

Khaya anthotheca . Previous studies have demonstrated that K . anthotheca bark contains biologically active compounds like gedunins, mexicanolide, phragmalin, and andirobins [ 98 ]. One limonoid identified in the species, anthothecol, has anti-cancer properties [ 99 ]. A study by Obbo et al. [ 100 ] on K . anthotheca bark collected in the Budongo Forest, found strong antiprotozoal activity against Plasmodium falciparum (IC 50 0.96 μg/mL) and Trypanosoma brucei rhodesiense (IC 50 5.72 μg/mL). A related species, K . senegalensis , has been shown to cause cell lysis in some gram-negative bacteria, including Salmonella Typhimurium , Escherichia coli , Shigella sp. and Salmonella sp., by targeting cytoplasmic membranes [ 101 ].

In our antibacterial library screen, of all extracts tested, only the methanol-water extract inhibited growth of A . baumannii (although no IC 50 values were reached in dose-response). The methanol-water extract also inhibited the growth of E . coli (DSM 498) in the library screen, as did the ethyl acetate (eE088) extract, though again no IC 50 values were reached. In our antibacterial dose-response assays, all extracts of K . anthotheca stem bark and resin exhibited strong inhibition against the Gram-positive E . faecium . The most active extract against this strain, which was also the strongest antibacterial result reported in this study, was methanol-water (mwE088) (IC 50 : 16 μg/mL; MIC: 32 μg/mL). All extracts of this species were also found to inhibit E . coli (DSM 1576) in the dose-response experiments, with the methanol-water extract once again also showing the strongest inhibition (IC 50 : 16 μg/mL; MIC: 256 μg/mL). This extract also inhibited the growth of S . maltophilia (IC 50 : 64 μg/mL) in the library screen. Only weak inhibition was found against the food pathogen S . enterica ( n -hexane extract, IC 50 : 256 μg/mL).

K . anthotheca exhibited potent anti-inflammatory activity. Of all extracts tested, the methanol-water K . anthotheca extract (mwE088) displayed the strongest COX-2 inhibition activity (IC 50 : 0.55 μg/mL). Past phytochemical studies on methanol and ethanol-water stem bark extracts from the related species, K . senegalensis , revealed many phenolic compounds, including flavonoids and tannins e.g., [ 101 , 102 ]. Flavonoids act on the inflammatory response, and may block molecules like COXs, cytokines, nuclear factor-кB and matrix metalloproteinases [ 103 ]. Some tannins have also been proven to have strong free radical-scavenging and antioxidant activities [ 104 ]. These compounds are antagonists of particular hormone receptors or inhibitors of particular enzymes such as COX enzymes [ 103 ]. If Khaya species are phytochemically similar, this could help explain K . anthotheca ’s strong COX-2 inhibitory activity.

Across Africa, K . anthotheca is traditionally used for ailments including allergies, fever, headaches, jaundice, bacterial infections, and as a disinfectant for bleeding wounds [ 105 – 107 ]. Our behavioral observations suggest that this species is also a common resource for Sonso chimpanzees, with a total of 65 feeding events recorded throughout the first field season. Of these events, several involved individuals with imbalanced health states (see Table 1 : K . anthotheca ) . On at least three independent occasions, K . anthotheca bark and resin were consumed by wounded individuals. Two adult females on different days tested positive for leukocytes on urinalysis tests within hours of ingesting K . anthotheca , suggesting the presence of infection. One of these individuals was also experiencing severe diarrhea the day prior, the other was found to have trace levels of blood in her urine. A juvenile female with a persistent cough was also observed consuming K . anthotheca bark. On several occasions individuals with high parasite loads or diverse species infection were observed targeting this resource while shedding tapeworm proglottids ( Bertiella sp.). An elderly female was also observed eating bark and resin a few hours prior to leaf-swallowing, a well-established self-medicative behavior known to rid the gut of endoparasites [ 9 , 23 ]. The frequency of K . anthotheca ingestion in the Sonso diet during this period, suggests that individuals have consistent exposure to the antibacterial and anti-inflammatory compounds present in this species. Whether this is a case of passive prevention through intake of a medicinal food, or therapeutic self-medication for a common and wide-spread condition will need further investigation. If used therapeutically, our results suggest this species could be used for treating wounds, bacterial or infections, and/or reducing internal parasite loads.

Christella parasitica.

Extracts of C . parasitica produced notably high anti-inflammatory activity in COX-2 testing, with the methanol-water extract (mwE087) achieving an IC 50 value of 0.81 μg/mL. This same extract, however, exhibited the lowest general activity in the antibacterial library screen. The only antibacterial activity from this species was on E . coli (DSM 498) by the ethyl acetate and n- hexane extracts (eE087; hE087), and on E . coli (DSM 1576) by the n-hexane extract (hE087). The n -hexane extract reached an IC 50 of 128 μg/mL in dose-response assays with no MIC value. Prior to this study, there had been limited pharmacological testing on C . parasitica (though see [ 108 ]), so comparison across studies is not possible.

When we considered the associated behavioral observation involving C . parasitica , we found a notable relevance to our pharmacological results (see Table 1 : C . parasitica , Case 1 ). This observation involved a wounded Sonso adult male (PS) travelling outside of his core area with a large group. It was unclear if this was an inter-community patrol. PS had been observed earlier in the day with a severe hand injury which impacted his mobility, though no open wound was observed. PS separated himself from the group and moved a few meters to a patch of ferns where he began consuming the leaflets. The bout lasted approximately 3-minutes. No other group members were observed feeding on this species, and this was only the second case of fern ingestion reported in Budongo in over 30-years of observations (unpublished site data). Health states of individuals from the past event were unfortunately not recorded. Whether or not C . parasitica ’s highly anti-inflammatory properties were the principal motivator for the selection of this species remains unknown, however, regardless of intention, this plant may have benefitted PS by reducing pain and swelling in his injured hand.

Syzygium guineense.

S . guineense bark and leaves have both previously been found to exhibit a range of pharmacological activity, reviewed by Uddin et al. [ 109 ]. The antioxidant, analgesic, and anti-inflammatory activities of this plant have been attributed to flavonoids, tannins, saponins, carbohydrates, alkaloids, and cardiac glycosides in the extracts [ 109 – 112 ]. In our assays, S . guineense bark exhibited high antibacterial growth inhibition effects in vitro . The methanol-water bark extract (mwE098a) showed some level of inhibition against all bacteria tested in the dose-response assays, except for E . faecium and S . enterica . This was also the only extract, out of all tested, to inhibit growth of P . aeruginosa (IC 50 : 64 μg/mL; MIC: >256 μg/mL) a pathogen known to cause infections in the blood, lungs, and other body parts after surgeries [ 113 ], and was one of two extracts to reach a MIC value against S . maltophilia (IC 50 : 32μg/mL; MIC: 256 μg/mL). The other extract to reach a MIC value was the ethyl acetate S . guineense bark extract (eE098a; IC 50 : 64 μg/mL; MIC: 256 μg/mL). All bark and leaf extracts showed strong inhibition against E . coli (DSM 1576) in the dose-response assays, with the strongest results coming from the methanol-water extracts (mwE098a and mwE098b). All bark and leaf extracts of this species, except for the n -hexane bark extract (hE098a), inhibited E . cloacae , and were the only extracts in the study to do so. E . cloacae , while part of normal intestinal flora, can cause UTI’s and respiratory infections in humans [ 114 ]. S . guineense extracts were also the only extracts to inhibit A . baumannii at a concentration <256 μg/mL, with the methanol-water bark extract showing the strongest inhibition. A . baumannii can cause infections in wounds, blood, urinary tracts, and lungs [ 115 ]. The efficacy of methanolic extracts from this species suggests that the active compounds are polar molecules. In the anti-inflammatory COX-2 inhibition dose-response assays, only the n -hexane bark extract displayed strong inhibitory effects (IC 50 : 2.42 μg/mL), while the other extracts failed to exhibit significant activity during the pre-screening or ≥ 50% inhibition at 10 μg/mL. The COX-2 inhibition assays showed no inflammatory inhibition amongst leaf extracts at tested concentrations.

S . guineense can be found throughout Sub-Saharan Africa and is a common traditional medicine, for malaria [ 116 ]. The bark is also used for stomach aches, diarrhea, internal parasites, and infertility [ 68 , 109 ]. Ingestion of S . guineense bark is rare in Budongo, with no direct observations in either community throughout the study period, and only six total cases between 2008–2021 documented in the site’s long-term data. No observations of leaf ingestion of this species have ever been reported. The infrequent ingestion of S . guineense bark implies a more targeted use, making it unlikely to be a medicinal food. Instead, our pharmacological findings make this resource a strong candidate as a putative, therapeutic self-medicative resource. Unfortunately, as there is currently no health data associated with individuals who have recently consumed S . guineense bark, we do not yet know which properties chimpanzees may be targeting. However, based on pharmacological results, we recommend further investigation into this species as a curative agent for respiratory-related infections.

Scutia myrtina.

Kritheka et al. [ 117 ] in their study on the bioactivity of S . myrtina , found in vivo evidence that this species possesses dose-dependent anti-inflammatory, antimicrobial, and antifungal properties. Across our antibacterial assays, the bark sample of this species collected from the stem inhibited E . faecium (eE089a) and E . coli DSM 1576 (eE089a; mwE089a) in dose-response tests at concentrations ≤256 μg/mL. The refuse sample, collected from the ground below the plant’s stem, inhibited A . baumannii (hE089b), E . faecium (eE089b), and E . coli DSM 1576 (mwE089b; eE089b; hE089b) in dose-response tests below the specified concentration. Interestingly, the refuse sample inhibited more bacteria species overall than the fresh bark. The most potent antibacterial growth inhibition effects came from the ethyl acetate bark sample against E . faecium (eE089a; IC 50 : 64 μg/mL), though no MIC value was reached. In the COX-2 inhibition assays, the n- hexane bark extract had the fifth strongest inhibitory effect in vitro (hE089a; IC 50 : 1.19 μg/mL) out of all samples, while the ethyl acetate refuse bark sample was less potent, though still moderately active (E089b; IC 50 : 7.49 μg/mL).

As far as the authors know, this is the first published report presenting both behavioral and pharmacological evidence for S . myrtina bark as a putative medicinal resource amongst free-ranging chimpanzees (though see [ 118 ] for evidence based on food-combinations). Our behavioral observations indicate that an individual with a diverse and intense parasite infection deliberately sought out the bark of this species. The Budongo chimpanzees may, therefore, utilize S . myrtina as an anthelminthic. Across traditional accounts from multiple regions, S . myrtina is commonly used by people as an anthelminthic to treat intestinal worms [ 68 ], while aerial parts are also used to treat various bacterial infections. As we were not able to conduct urinalysis on the consumer during or after this event, we cannot determine whether the individual also harbored a bacterial infection at the time of ingestion. However, this possibility cannot be ruled out. Based on these findings, we propose S . myrtina be added to the list of putative chimpanzee self-medication behaviors as a treatment for internal parasites, and we encourage further exploration into the other specific chimpanzee health conditions that this species may help ameliorate.

Assessment of putative self-medicative behaviors

We synthesized pharmacological and behavioral evidence to assess therapeutic use of species associated with bark feeding, dead wood eating, and pith stripping behaviors. A summary of the antibacterial and anti-inflammatory results for each species is reported in S3 Table in S2 File . Overall, stem bark and dead wood samples were notable for their activity. Bark samples from every species showed >40% antibacterial inhibition against at least one bacterial strain. This activity was also true of the dead wood samples. When plant parts of the same species were tested ( S . guineense and F . exasperata ), barks generally exhibited more potent antibacterial and COX-2 inhibition activity than the leaves, likely to do with the higher concentration of plant secondary metabolites in bark. Our findings offer strong support that bark and dead wood eating of certain species could constitute novel self-medicative behaviors in wild chimpanzees. We also encourage more investigation into the bioactivity of non-bitter pith stripping, as the pith of A . polystachius showed strong antibacterial activity against E . faecium (hE099; IC 50 : 32 μg/mL; MIC: 128 μg/mL), and the piths of both A . polystachius and M . leucantha demonstrated significant anti-inflammatory properties at low concentrations. Future primatological research should prioritize the establishment of multi-disciplinary long-term projects that look systematically at health states of individuals who engage in bark, dead wood, and pith ingestion behaviors. We also encourage further pharmacological testing on other species used for these behaviors in Budongo and across primate field sites.

Drug discovery

Multidisciplinary studies on this topic have potential to lead to the discovery of new medicines which may benefit our own species [ 119 – 122 ]. Historically, PSMs have played a major role in the development of modern human medicine, and even today, a large portion of medicines are derived either directly or indirectly from plants and other natural materials [ 123 – 127 ]. Antimicrobial resistance is rising to dangerously high levels according to the World Health Organization [ 128 ] requiring the rapid creation of new antibacterial treatments. Infections caused by multi-drug resistant bacteria kill hundreds of thousands of people annually. Our findings of strong antibacterial growth inhibition across numerous plant species growing in Budongo have promising implications for our ability to discover novel compounds in existing forest habitats. Extracts should also be tested against additional bacteria and for anti-virulence effects, e.g., inhibition and disruption of biofilm formation, quorum sensing and toxin production, pursuing development of new therapeutic strategies that apply less evolutionary pressure, likely resulting in emergence of less antibiotic resistances in the future. Phytochemical characterization using advanced techniques, such as LC-ToF-MS and NMR, as well as potentially AI-assisted untargeted metabolomics approaches, are now needed to identify substances present in the most active extracts. This may eventually lead to the isolation and structure elucidation of yet unknown active ingredients and make way for determining their pharmacological selectivity and toxicity, while also taking potential synergistic effects into account.

Simultaneously, we are currently faced with a pressing need for more effective treatments to combat symptoms of acute inflammation and mediate long-term consequences of chronic inflammatory diseases [ 129 ]. The prostaglandin-producing cyclooxygenase-2 (COX-2) mediates and regulates pain, fever, wound inflammation, and many other medical disorders, as it plays a crucial role in the host organism’s defense against pathogens and injury. COX-2 inhibition has the same mechanism of action as non-steroidal anti-inflammatory drugs (NSAIDs). While inflammation is a normal part of the body’s defense against injury or infection, it can be damaging when occurring in healthy tissues or over a protracted period. Chronic inflammation can lead to cardiovascular diseases (CVD) and cancer, the two leading global causes of death [ 130 ]. Past studies have shown that the IC 50 values of Aspirin and ibuprofen (pure compounds and common NSAIDs) are 210 μg/mL and 46 μg/mL respectively for COX-2, and 5 μg/mL and 1 μg/mL respectively for COX-1 [ 131 , 132 ]. The in vitro COX-2/COX-1 selectivity ratio for Aspirin and ibuprofen is 42 and 46 respectively. Surprisingly, the 17 most active extracts in our COX-2 assays display lower IC 50 values than these popular NSAIDs, meaning our extracts have more potent inhibitory effects on the inhibition of COX-2 than the most common anti-fever and anti-pain drugs on the market. While COX-1 assays were beyond the scope of this study, future research should investigate COX-1 inhibition activity of these 17 extracts to calculate COX-2/COX-1 selectivity ratios. Doing so will allow for preliminary assessment of potential side effects, selectivity, and efficacy before future in vivo experiments can commence.

Future directions

Future research on this topic would benefit from the inclusion of control samples (plants or plant parts not consumed by chimpanzees); however, in this study, assay costs were a prohibiting factor. Additional information regarding the nutritional and mineral content of the species mentioned in this study is needed to better understand the motivations for ingestion. However, bioactivity and nutritional/mineral content are by no means mutually exclusive. It is, therefore, highly likely that these resources provide multiple benefits to consumers.

Future studies should also consider ecological variables. For example, different individual plants of the same species should be tested across habitat types to determine whether bioactivity varies based on location, age, life history, or time of harvest. Situating samples in their ecological context will provide a better understanding of whether chimpanzees select resources based on species alone, or other more nuanced criteria. Lastly, climatic studies in combination with pharmacological testing should examine how climate change may impact bioactivity of these plants, as shifting weather patterns have already been shown to alter nutritional content [ 133 ]. This information will be critical for establishing protected habitats that can sustain healthy, wild, primate populations.

Conclusions

As we learn more about the pharmacological properties of plants ingested by chimpanzees in the wild, we can expand our understanding of their health maintenance strategies. Our results provide pharmacological evidence, from in vitro assays of plant parts consumed by wild chimpanzees collected in situ , for the presence of potent bioactive secondary plant metabolites in Budongo chimpanzee diets for a variety of potential illnesses previously not considered. Whether these resources are consumed intentionally as a form of therapeutic self-medication or passively as medicinal foods, must be assessed on a case-by-case basis, taking behavioral observations into account.

For the field of zoopharmacognosy to progress, we encourage continued multidisciplinary collaboration between primatologists, ethnopharmacologists, parasitologists, ecologists, and botanists [ 9 ]. Beyond improving our broad understanding of chimpanzee health maintenance, multidisciplinary studies will benefit our own species, potentially leading to the discovery of novel human medicines to combat the looming problem of growing drug-resistance. For this to happen, however, it is imperative that we urgently prioritize the preservation of our wild forest pharmacies as well as our primate cousins who inhabit them.

Materials availability

Voucher specimens for each species were deposited at the Makerere University Herbarium in Kampala, Uganda for taxonomic identification and storage. A duplicate set was deposited at the University of Oxford Herbarium for permanent storage.

Supporting information

S1 fig. budongo chimpanzees consuming resources tested in this study..

a.) IN eating K . anthotheca bark and resin b.) MZ eating S . myrtina bark c.) KC stripping A . polystachyus pith d.) MB eating C . patens dead wood e.) OZ eating S . guineense bark (post-study period) g.) MZ eating F . exasperata bark.

https://doi.org/10.1371/journal.pone.0305219.s001

S2 Fig. Generalized multi-method workflow used in this study.

https://doi.org/10.1371/journal.pone.0305219.s002

S3 Fig. Voucher samples collected in duplicate.

a . ) C . alexandri (00243133G) b . ) A . polystachius (00243136J) c . ) W . elongata (00243129L) d . ) C . parasitica (00243122E) e . ) K . anthotheca (00243123F) f . ) F . variifolia (51195) g . ) M . leucantha (51203) h . ) A . boonei (51204) i . ) D . dewevrei (00243132F) j . ) S . guineense (00243135I) k . ) S . myrtina (00243128K) l . ) F . exasperata (00243130D).

https://doi.org/10.1371/journal.pone.0305219.s003

S4 Fig. Plate layouts for growth inhibition assays.

[Top] Library Screen: done in 96-wells-mikrotiterplate; AB: Antibiotic as positive control; DMSO: vehicle control / negative control; GC: growth control: containing working culture, to check whether the bacterium grew/active; [Bottom] Dose-Response: done in descending concentration of samples, DMSO, and antibiotic. MB: Media blank, consisted of CAMHB as negative/ sterile media control; DMSO as negative/ vehicle control; GC: growth control, consisted of working culture.

https://doi.org/10.1371/journal.pone.0305219.s004

S5 Fig. ELISA assay setup for anti-inflammatory assay.

https://doi.org/10.1371/journal.pone.0305219.s005

S1 File. Supplementary materials: Methods .

https://doi.org/10.1371/journal.pone.0305219.s006

S2 File. Supplementary tables.

https://doi.org/10.1371/journal.pone.0305219.s007

Acknowledgments

We are grateful to all the field staff working in Budongo who provided invaluable instruction and guidance, generously sharing both scientific insight and traditional knowledge. This study could not have been done without their contributions. Specifically, we would like to thank members of the Perspectives Collective: Chandia Bosco, Monday Mbotella Gideon, Adue Sam, Asua Jackson, Steven Mugisha, Atayo Gideon, and Kizza Vincent, and Walter Akankwasa, as well as site director David Eryenyu. We would also like to thank Godwin Anywar for his assistance with plant identification at the Makerere Herbarium, Stephen Harris at the University of Oxford’s Herbarium for his facilitation of voucher storage, and the Natural History Museum in London for their aid in parasite identification. We are grateful to Vernon Reynolds who founded the field site and to the Royal Zoological Society of Scotland for providing core support. We also gratefully acknowledge the Uganda Wildlife Authority and the Uganda National Council for Science and Technology for granting permission to conduct research in Uganda. Lastly, thank you to the staff and students at Neubrandenburg University of Applied Sciences who made this collaboration possible, and to research assistant, Finn Freymann, for his help with botanical extractions.

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The blood microbiome is probably not real.

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Up until recently, if bacteria were detected in your blood you would be in a world of trouble. Blood was long considered to be sterile, meaning free of viable microorganisms like bacteria. When disease-causing bacteria spread to the blood, they can cause a life-threatening septic shock.

But the use of DNA sequencing technology has allowed researchers to more easily detect something that had been reported as early as the late 1960s: bacteria can be found in the blood and not cause disease.

As we begin to map out and understand the complex microbial ecosystem that lives in our gut and elsewhere in the body, we contemplate an important question: is there such a thing as a blood microbiome?

Detecting a fingerprint in the blood

Our large intestine is not sterile; it is teeming with bacteria. But there are parts of the body that were long thought to be devoid of microorganisms. The brain. Bones. A variety of internal fluids, like our synovial fluid and peritoneal fluid. And, importantly, the blood.

Blood is made up of a liquid called plasma filled with red blood cells, whose main function is to carry oxygen to our cells. It also transports white blood cells, important to monitor for and fight off infections, as well as platelets, involved in clotting. 

In the 1960s, a team of Italian researchers published  multiple papers  describing “mycoplasm-like forms”—meaning shapes that look like a particular type of bacteria that often contaminate cells cultured in the lab—in the blood of healthy people. This finding was confirmed in 1977 by a different team, which reported that  four out of the 60 blood samples  they had drawn from healthy volunteers showed bacteria growing in them. These types of tests, however, were rudimentary compared to what we have access to now. In the 2000s, they were mostly supplanted by DNA testing.

While we can sequence the entire DNA of any bacteria found in the blood, the technique most often used is 16S rRNA gene sequencing. I have always admired physicists’ penchant for quirky names: gluons, neutrinos, and charm quarks. Molecular biologists, by comparison, tend to be more sober. Yes, we have genes like  Sonic hedgehog  and proteins called scramblases; usually, though, we have to contend with the dryness of “16S rRNA.” You see, RNA is a molecule with many uses. Messenger RNA (or mRNA) acts as a disposable copy of a gene, a template for the production of a specific protein. Transfer RNA (or tRNA) actually brings the building blocks of a protein to where they are being assembled. And ribosomal RNA (or rRNA) is the main component of the giant protein factories in our cells known as ribosomes. One of its subunits is made up of, among others, a particular string of RNA known as the 16S rRNA.

The cool thing about the gene that codes for this 16S rRNA molecule is that it is very old and it mutates at a slow rate. By reading its precise sequence, scientists can tell which species it belongs to. Most of the studies of the putative blood microbiome use this technique to tell which species of bacteria are present in the blood being tested. The limitation of this test, however, is that dead bacteria have DNA too. The fact that DNA from the 16S rRNA gene of a precise bacterial species was detected in someone’s blood does not mean these bacteria were alive. For there to be a microbiome in the blood, these microorganisms need to live.

Which brings us to another important point of discussion. In order for scientists to agree that a blood microbiome exists, they first need to decide on the definition of a microbiome, and this is still a point of contention. In 2020, while companies were more than happy to sell hyped-up services testing your gut microbiome and claiming to interpret what it meant for your health, actual experts in the field met to agree on just what the word meant. “We are lacking,” they  wrote , “a clear commonly agreed definition of the term ‘microbiome’.” For example, do viruses qualify? A microbiome implies life but viruses live on the edge, pun intended: they have the genetic blueprint for life yet they cannot reproduce on their own.

These experts proposed that the word “microbiome” should refer to the sum of two things: the microbiota, meaning the living microorganisms themselves, and their theatre of activity. It’s like saying that the Earth is not simply the life forms it houses, but also all of their individual components, and the traces they leave behind, and the environmental conditions in which they thrive or die. The microbiome is made up of bacteria and other microorganisms, yes, but also their proteins, lipids, sugars, and DNA and RNA molecules, as well as the signalling molecules and toxins that get exchanged within their theatre. (This is where viruses were sorted, by the way: not as part of the living microbiota but as belonging to the theatre of activity of the microbiome.)

The microbiome is a community, and this community has a distinct habitat.

So, what does the evidence say? Is our blood truly host to a thriving community of microorganisms or is something else going on?

Transient and sporadic

Initial studies of the alleged blood microbiome were  small . The amounts of bacteria that were being reported based on DNA sequencing were tiny. If this microbiome existed, it seemed sparse, more  “asteroid field in real life”  than “asteroid field in the movies.”

An issue looming over this early research is that of contamination. If bacteria are detected in a blood sample, were they really in the blood… or did they contaminate supplies along the way? When blood is drawn, the skin, which has its own microbiome, is punctured. The area is usually swabbed with alcohol to kill bacteria, and the supplies used should be sterile, but suffice to say that from the blood draw to the DNA extraction to the DNA amplification to the sequencing of this DNA, bacteria can be introduced into the system. In fact, it is such common knowledge that certain bacteria are found inside of the laboratory kits used by scientists that this ecosystem has its own name: the kitome. One way to rule out these contaminants is to simultaneously run negative controls alongside samples every step of the way, to make sure that these negative controls are indeed free of bacteria. But early papers rarely reported when controls were used.

Last year, results from what purports to be the largest study ever into the question of whether the blood microbiome exists were  published in  Nature Microbiology . A total of 9,770 healthy individuals were tested. The conclusion? Yes, some bacteria could be found in their blood, but the evidence contradicted the claim of an ecosystem. In 84% of the samples tested, no bacteria were detected. In most of the other samples, only one species was found. In an ecosystem, you would expect to see species appearing together repeatedly, but this was not the case here. And the species they found most often in their samples were known to contaminate these types of laboratory experiments.

So, what were the few bacteria found in the blood and not recognized as contaminants doing there in the first place if they were not part of a healthy microbiome? The authors lean toward an alternative explanation that had been floated for many years: these bacteria are transient. They end up in the blood from other parts of the body, either because of some minor leak or through their active transportation into the blood by agents such as dendritic cells. Like pedestrians wandering off onto the highway, these bacteria do not normally live in the blood but they can be seen there when we look at the right moment.

Putting the diagnostic cart before the horse

This blood microbiome story could end here and simply be an interesting example of scientific research homing in on a curious finding, testing a hypothesis, and ultimately refuting it (or at the very least providing strong evidence against it). But given the incentives of modern research and the social-media spotlight cast on the academic literature, there are two slightly worrying angles here that merit discussion.

Scientists are more and more incentivized to find practical applications for their research. It’s not enough, for example, to study bacteria that survive at incredibly high temperatures; we must be assured that the  DNA replication enzyme  these bacteria possess will one day be used in laboratories all over the world to conduct research, identify criminals, and test samples for the presence of a pandemic-causing coronavirus.

In researching this topic, I came across many papers claiming the existence of “blood microbiome signatures” for certain diseases that are not known to be infectious. We are thus not talking about infections leaking in the blood and causing sepsis. I saw reports of signatures for  cardiovascular disease ,  liver disease ,  heart attacks , even for  gastrointestinal disease  in dogs .  The idea is that these signatures could soon be turned into (profitable) diagnostic tests. The problem, of course, is that these studies are based on the hypothesis that a blood microbiome is real; that its equilibrium can be affected by disease; and that these changes can be reliably detected and interpreted.

But if the blood microbiome is imaginary, we are just chasing ghosts. This is not unlike the time that scientists were publishing signatures of microRNAs in the blood for every possible cancer. When I looked at the published literature in grad school, I realized that the multiple signatures reported for a single cancer  barely overlapped . They were just chance findings. Compare enough variables in a small sample set and you will find what appears to be an association.

My second concern is that the transitory leakage of bacteria into the blood, as evidenced by the recent  Nature Microbiology  paper, will be used as confirmation of a pseudoscientific entity: leaky gut syndrome. At the end of their paper, the researchers  hypothesize  that these bacteria end up in the blood because the integrity of certain barriers in the body are compromised during disease or during periods of stress. The “net” in our gut gets a bit porous, and some of our colon’s bacteria end up in circulation, though they are not causing disease as far as we can tell. A form of leaky gut is known to exist  in certain intestinal diseases , likely to be a consequence and not a cause. But leaky gut syndrome, favoured by non-evidence-based practitioners, does not appear to be real, yet many websites portray it as the one true cause of all diseases, a real epidemic. Nuanced scientific findings have a history of being stolen, distorted, and toyed with by fake doctors to give credence to their pet theories. Though I have yet to see examples of it, I suspect work done on this hypothesized blood microbiome will similarly get weaponized.

You have been warned.

Take-home message: - Our blood was long considered to be sterile, meaning free of viable microbes, unless a dangerous infection leaked into it, causing sepsis - Studies have provided evidence for the presence of bacteria in the blood of some healthy humans, leading to the hypothesis that, much like in our gut, our blood is host to a microbiome - The largest study ever done on the topic provided strong evidence against this hypothesis. It seems that when non-disease-causing bacteria find themselves in our blood, it is temporary and occasional

@CrackedScience

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Department and University Information

Office for science and society.

1. Introduction

2. materials and methods, 4. discussion, 5. conclusion and outlook, supporting information.

research papers \(\def\hfill{\hskip 5em}\def\hfil{\hskip 3em}\def\eqno#1{\hfil {#1}}\)

Factors affecting macromolecule orientations in thin films formed in cryo-EM

a National Centre for Biological Sciences, Tata Institute of Fundamental Research, GKVK Post, Bellary Road, Bengaluru 560 065, India * Correspondence e-mail: [email protected]

The formation of a vitrified thin film embedded with randomly oriented macromolecules is an essential prerequisite for cryogenic sample electron microscopy. Most commonly, this is achieved using the plunge-freeze method first described nearly 40 years ago. Although this is a robust method, the behaviour of different macromolecules shows great variation upon freezing and often needs to be optimized to obtain an isotropic, high-resolution reconstruction. For a macromolecule in such a film, the probability of encountering the air–water interface in the time between blotting and freezing and adopting preferred orientations is very high. 3D reconstruction using preferentially oriented particles often leads to anisotropic and uninterpretable maps. Currently, there are no general solutions to this prevalent issue, but several approaches largely focusing on sample preparation with the use of additives and novel grid modifications have been attempted. In this study, the effect of physical and chemical factors on the orientations of macromolecules was investigated through an analysis of selected well studied macromolecules, and important parameters that determine the behaviour of proteins on cryo-EM grids were revealed. These insights highlight the nature of the interactions that cause preferred orientations and can be utilized to systematically address orientation bias for any given macromolecule and to provide a framework to design small-molecule additives to enhance sample stability and behaviour.

Keywords: cryo-EM ; thin films ; preferred macromolecular orientation ; surfactants ; temperature .

EMDB references: CRP pentamer with CTAB, EMD-37864 ; CRP decamer with CTAB, EMD-37865 ; PaaZ with CTAB at 4°C, EMD-37866 ; catalase with SLS, EMD-37952 ; spike with CTAB, EMD-37953 ; catalase at 20°C, EMD-37954 ; catalase at 4°C, EMD-37955 ; catalase with CTAB, EMD-37956 ; β-galactosidase, no tag, EMD-39808 ; β-galactosidase, with tag, EMD-39809

PDB references: CRP pentamer with CTAB, 8wv4 ; CRP decamer with CTAB, 8wv5 ; PaaZ with CTAB at 4°C, 8wv6 ; catalase with SLS, 8wzh ; spike with CTAB, 8wzi ; catalase at 20°C, 8wzj ; catalase at 4°C, 8wzk ; catalase with CTAB, 8wzm

To achieve this goal, we tested some commonly used surfactants with different properties on a set of five proteins: C-reactive protein (CRP) pentamers, CRP decamers, catalase, PaaZ and spike. In addition, we explored the effect of the presence of the histidine tag for spike and β -galactosidase and of physical factors such as the temperature during the sample-application step for catalase and PaaZ. We also serendipitously observed an effect of the grid hole dimensions of the holey carbon grid on the orientation distribution of catalase and discuss this briefly. Through this analysis, we identified factors that affect and determine the behaviour of the macromolecule on grids before freezing and studied their effects with a focus on the preferred orientation problem. This account highlights the factors that contribute to orientation bias and provides valuable information that can assist in achieving the optimal freezing conditions for any given macromolecule.

2.1. Source of proteins

Human C-reactive protein (catalogue No. C4063) and human erythrocyte catalase (catalogue No. C3556) were obtained from Sigma–Aldrich. The protein samples were either concentrated using an Amicon 100 kDa concentrator or diluted in respective buffers for grid freezing. All detergent stocks were made in ultrapure water and dilutions were made and used on the day of the experiment.

The SARS-CoV-2 S plasmid was a kind gift from the Krammer laboratory at Icahn School of Medicine, Mount Sinai. The spike gene was amplified from the plasmid and subcloned in the BacMam vector with a C-terminal HRV 3C cleavage tag followed by a seven-histidine and twin Strep tag. Bacmid DNA and virus were prepared as described in the Invitrogen Bac-to-Bac manual. After two generations of amplification in Sf9 cells, the V2 virus was used for transfection of HEK293F cells at a density of 2 million per millilitre. Sodium butyrate (4 m M ) was added to enhance the production of protein 8 h post-infection. The medium supernatant containing the secreted spike protein was harvested on day 3 by centrifuging the cells at 150 g for 10 min. The medium was incubated with pre-equilibrated Ni–NTA (Qiagen) beads at room temperature for 1–2 h (1 ml of beads per 200 ml of medium). The Ni–NTA beads were washed with phosphate-buffered saline (PBS) containing 20 m M imidazole, followed by elution with 280 m M imidazole in PBS. The eluted protein was run on SDS–PAGE to assess its purity, further concentrated and injected onto a 24 ml Superdex 200 (Cytiva) size-exclusion column to exchange the buffer to 50 m M Tris pH 8, 200 m M NaCl, 1 m M DTT. To cleave the tag, the eluted fractions from Ni–NTA chromatography were diluted with 50 m M Tris pH 8, 200 m M NaCl, 1 m M DTT and incubated with HRV 3C protease overnight at 4°C, followed by reverse IMAC to obtain the spike protein without tag in the flowthrough. The flowthrough was concentrated using an Amicon 100 kDa concentrator, flash-frozen using liquid nitrogen and stored at −80°C until further use.

2.2. Grid preparation

6.3 µl of the protein was thawed on ice and 0.7 µl of 10× additive (surfactant) stock was added to obtain a final concentration of 1×. This sample was incubated on ice for 2–5 min and then centrifuged at 21 000 g for 20 min. Meanwhile, a Vitrobot Mark IV (Thermo Fisher Scientific) chamber was equilibrated at 20°C (unless stated otherwise) and 100% humidity. Quantifoil 1.2/1.3 or Quantifoil 0.6/1 grids were glow-discharged in a reduced-air environment with a PELCO easiGlow chamber using a standard setting of 25 mA current for 1 min. The grid was mounted on the Vitrobot Mark IV and 3 µl of sample was applied to the grid. A blotting time of 3–4 s, a wait time of 10 s and a blot force of 0 were used to obtain a thin film of the specimen. For data sets where grids were prepared at different temperatures, the protein was incubated on a thermal block at the required temperature for 3–7 min before applying it to the grid. The Vitrobot chamber was maintained at the required temperature and 100% humidity. The blot time, blot force and wait time were kept constant.

2.3. Grid screening and data collection

Summary of the parameters for data sets collected under different conditions Protein Condition Grid type (Quantifoil) Buffer composition Protein concentration (mg ml ) Detector Box size (pixels) Pixel size CRP pentamer and decamer No additive 1.2/1.3 20 m Tris pH 8, 280 m NaCl, 5 m CaCl , 0.03% NaN 2.1 Falcon 3 256 1.07 CTAB 1.2/1.3 2.6 Falcon 3 256 1.07 SLS 1.2/1.3 2.6 K2 320 1.08 Tween 20 1.2/1.3 3.6 K2 320 1.08 Tween 80 1.2/1.3 6.8 K2 320 1.08 A8-35 1.2/1.3 3.6 Falcon 3 320 1.07 Catalase No additive, 20°C 1.2/1.3 50 m Tris pH 8 0.625 Falcon 3 256 1.07 CTAB 1.2/1.3 3.4 K2 320 1.08 SLS 1.2/1.3 3.4 Falcon 3 256 1.07 Tween 20 1.2/1.3 3.4 K2 320 1.08 Tween 80 1.2/1.3 4.1 Falcon 3 320 1.07 A8-35 1.2/1.3 3.4 Falcon 3 320 1.07 4°C 1.2/1.3 0.625 Falcon 3 256 1.07 37°C 1.2/1.3 0.625 Falcon 3 320 1.38 4°C 0.6/1 0.625 Falcon 3 320 1.07 20°C 0.6/1 0.625 Falcon 3 256 1.07 PaaZ No additive, 4°C 0.6/1 25 m HEPES pH 7.4, 50 m NaCl 0.8 Falcon 3 320 1.07 No additive, 20°C 0.6/1 0.8 Falcon 3 256 1.07 No additive, 37°C 0.6/1 0.8 Falcon 3 — 1.38 CTAB, 4°C 0.6/1 0.8 Falcon 3 256 1.07 Spike With tag, no additive 0.6/1 50 m Tris pH 8, 200 m NaCl, 1 m DTT 1 Falcon 3 256 1.07 With tag, with CTAB 0.6/1 1.3 Falcon 3 320 1.07 Without tag, no additive 0.6/1 2 Falcon 3 256 1.07 Without tag, with CTAB 0.6/1 2 Falcon 3 256 1.07 β-Galactosidase With tag, no additive 0.6/1 100 m Tris pH 8, 200 m NaCl, 5 m CaCl 2.5 m MgCl , 2 m β-ME 5 Falcon 3 320 1.07 Without tag, no additive 0.6/1 5 Falcon 3 320 1.07 2.4. Data processing and model refinement 3.1. analysis of preferred views of selected macromolecules. Representative micrographs, with a few selected particles indicated with red circles, and 2D class averages of the test proteins used in this study. ( ) The C-reactive protein (CRP) pentamer adopts a preferred bottom view, which shows the pentameric arrangement of the monomers. ( ) The CRP decamer adopts a preferred side view, which shows the staggered arrangement of two CRP pentamers stacked on top of each other. The same micrograph is used in ( ) and ( ). ( ) Catalase adopts a preferred top view, as seen in the micrograph and 2D class averages. ( ) SARS-CoV-2 spike adopts a preferred bottom view showing the trimeric arrangement. ( ) PaaZ adopts a preferred side view, as seen in the 2D class averages, and the micrograph shows occasional clumping of hexamers on the grids. ( ) β-Galactosidase with an N-terminal polyhistidine tag adopts a preferred side view, as seen in the 2D class averages, and the micrograph shows aggregation on grids. For the above data sets, the catalase and PaaZ grids were prepared at 4°C and all other grids were prepared at 20°C. 3.2. Surfactants affect macromolecule orientation distributions in a charge-dependent manner Properties of the surfactants used in this study Additive Charge Ionic or non-ionic CMC Concentration used Aggregation number Molecular weight (Da) Alkyl-chain length Saturation in alkyl chain CTAB Positive Ionic 1 m (0.04%) 0.054 m (0.002%) 170 364 16 Saturated SLS Negative Ionic 14.6 m (0.42%) 1.37 m (0.04%) — 293 12 Saturated Tween 20 Neutral Non-ionic 0.06 m (0.007%) 0.04 m (0.005%) 80 1228 12 Saturated Tween 80 Neutral Non-ionic 0.012 m (0.002%) 0.038 m (0.005%) 58 1310 18 Unsaturated A8-35 Negative Ionic NA 0.01% NA ∼9000 NA NA Comparison of parameters for no-additive and surfactant-additive data sets Protein Condition No. of particles Resolution (Å) (half-map FSC 0.143) Efficiency of Fourier space coverage Sphericity CRP pentamer No additive 14601 18 0.78 NA CTAB 36353 3.3 0.80 0.98 SLS 31699 4.2 0.80 0.97 Tween 20 25674 3.3 0.80 0.86 Tween 80 32330 7.5 0.69 NA A8-35 26737 10 0.78 NA CRP decamer No additive 9419 20 0.52 NA CTAB 25992 3.5 0.85 0.98 SLS 59211 3.7 0.79 0.97 Tween 20 51784 4.0 0.78 0.92 Tween 80 36870 4.2 0.79 0.76 A8-35 104369 3.5 0.78 0.98 Catalase No additive 138000 2.7 0.72 0.96 CTAB 153336 2.8 0.76 0.97 SLS 33241 3.7 0.80 0.98 Tween 20 88395 2.9 0.78 0.98 Tween 80 92163 2.9 0.80 0.96 A8-35 122000 3.1 0.77 0.98 PaaZ No additive 51393 4.0 0.76 0.80 CTAB 89454 2.3 0.75 0.98 Orientation-distribution plots from (Scheres, 2012 ) of proteins upon the addition of surfactants with varying properties to the sample buffer before grid preparation. The reference structures of the respective proteins are generated by creating a surface representation in from models from PDB entries , , and . ( ) Changes in the CRP pentamer orientation distribution upon the addition of surfactants. The distributions are distinct from each other, except for Tween 20 and Tween 80, which have similar distributions. ( ) Changes in the CRP decamer orientation distribution upon addition; all surfactants lead to a similar even orientation distribution. ( ) Changes in the catalase orientation distribution upon the addition of surfactants, where the charged surfactants have distinct distributions (CTAB and SLS) and the neutral surfactants (Tween 20 and Tween 80) and A8-35 show similar distributions. ( ) Changes in PaaZ orientation distributions upon the addition of the cationic CTAB. The effects of SLS and Tween 20 on PaaZ were also tested, but visual inspection of the micrographs ( ) showed no improvement and no data were collected; therefore they are not included (marked by asterisks). The effects of Tween 80 and A8-35 on PaaZ were not tested. 3.3. The presence of a solvent-exposed polyhistidine tag affects protein orientations in thin films The effect of a polyhistidine affinity tag on the SARS-CoV-2 spike protein and β-galactosidase orientation distributions. The different parameters that are used to analyse the quality of the maps are shown next to the orientation plots. indicates the number of particles used for reconstruction, indicates the final resolution of the map, indicates the sphericity and indicates the efficiency of Fourier space coverage. ( ) The locations of the tags on the protein models are indicated by black stars. The models used as references are PDB entries and for the spike protein and β-galactosidase, respectively. ( ) The orientation-distribution plots of the spike protein change upon removal of the affinity tag, but the change is not sufficient to obtain an isotropic map. The addition of the cationic CTAB further alters the orientations of the spike protein without tag and leads to a more isotropic map. β-Galactosidase enzyme (bottom panel) orientations change upon removal of the affinity tag and lead to an isotropic high-resolution map without any additive. The unsharpened final combined maps are shown in grey in ( ). 3.4. The temperature of the incubation chamber during freezing affects protein orientations The effect of temperature during cryo-EM sample preparation of catalase and PaaZ. Micrographs, maps, orientation-distribution plots and the different parameters that are used to analyse the quality of the maps are shown. indicates the number of particles used for reconstruction, indicates the final resolution of the map, indicates the sphericity and indicates the efficiency of Fourier space coverage. ( ) Catalase orientation distributions change significantly when grids are blotted at different temperatures in the absence of any additive. ( ) PaaZ orientation distributions change slightly when grids are held and blotted at different temperatures in the absence of any additive. In the case of PaaZ, the condition with grids prepared at 4°C with CTAB as an additive is included for comparison as this combination led to a high-resolution isotropic map. It is evident from these observations that physical factors, such as the grid-preparation temperature, can affect protein behaviour and should be considered as an important screening condition when dealing with orientation bias along with surfactants. 3.5. High-resolution map of E. coli PaaZ in ice High-resolution cryo-EM map from PaaZ grids prepared at 4°C with CTAB additive. ( ) Comparison of the half-maps and map-versus-model FSCs of the PaaZ data set. ( ) The six coloured individually and in cartoon representation fitted into the cryo-EM map (transparent grey) of PaaZ. ( ) Electrostatic potential surface representation of the domain-swapped PaaZ dimer with waters modelled and shown as cyan spheres. ( ) ResLog plot of PaaZ with the experimental and theoretical numbers of particles required to reach a particular resolution. indicates the number of particles used for reconstruction, is the resolution and indicates the factor, as estimated by post-processing. 3 symmetry was applied for the reconstruction and the ResLog plot indicates the number of particles used, not the number of asymmetric units averaged. Supplementary Figures and Tables. DOI: https://doi.org/10.1107/S2059798324005229/rr5238sup1.pdf Acknowledgements We acknowledge the National Cryo-EM Facility, Bangalore for data collection, which is supported by the Department of Biotechnology (DBT/PR12422/MED/31/287/2014), and the computing facility in the Bangalore Life Science Cluster. We thank Professor Ramaswamy S and all of the laboratory members for critical reading of the manuscript. KRV is part of the EMBO Global Investigator Network. KRV acknowledges the discussion with Drs Pamela Williams and Judith Reeks, Astex, UK on β -galactosidase and the effect of tags. The authors declare no conflicts of interest. Funding information KRV acknowledges the support of the Department of Atomic Energy, Government of India under Project Identification No. RTI4006. SY acknowledges the graduate fellowship from TIFR/NCBS. This is an open-access article distributed under the terms of the Creative Commons Attribution (CC-BY) Licence , which permits unrestricted use, distribution, and reproduction in any medium, provided the original authors and source are cited. Follow Acta Cryst. D 360 IMAGES Results And Discussion In Research Example : Sharing of Research how to write thesis results and discussion Results And Discussion In Research Example : Sharing of Research Journal Article: Discussion : Broad Institute of MIT and Harvard 6 Writing the Discussion and Conclusion Sections Results and Discussion Explanation and Example VIDEO Dissertation discussion chapter HOW TO WRITE RESEARCH/THESIS RESULTS AND DISCUSSIONS, SUMMARY, CONCLUSION, & RECOMMENDATION Sample Research Paper Topics and Titles Overview of a Discussion Chapter CHAPTER 5 HOW TO WRITE RESULTS AND DISCUSSION- RESEARCH PAPER Differences Between Results and Discussion COMMENTS How to Write a Discussion Section Table of contents. What not to include in your discussion section. Step 1: Summarize your key findings. Step 2: Give your interpretations. Step 3: Discuss the implications. Step 4: Acknowledge the limitations. Step 5: Share your recommendations. Discussion section example. 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The results section should present the facts in an academic and unbiased manner, avoiding any attempt at analyzing or interpreting the data. Think of the results section as setting the stage for the ... PDF Discussion Section for Research Papers The discussion section is one of the final parts of a research paper, in which an author describes, analyzes, and interprets their findings. They explain the significance of those results and tie everything back to the research question(s). In this handout, you will find a description of what a discussion section does, explanations of how to ... Research Results Section Research results refer to the findings and conclusions derived from a systematic investigation or study conducted to answer a specific question or hypothesis. These results are typically presented in a written report or paper and can include various forms of data such as numerical data, qualitative data, statistics, charts, graphs, and visual aids. 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An example of research implications in discussion. 3.5. An example of limitations in discussion. Academic Phrases for Writing Results & Discussion Sections of a The results and discussion sections are one of the challenging sections to write. It is important to plan this section carefully as it may contain a large amount of scientific data that needs to be presented in a clear and concise fashion. The purpose of a Results section is to present the key results of your research. The Writing Center IMRaD Results Discussion. Results and Discussion Sections in Scientific Research Reports (IMRaD) After introducing the study and describing its methodology, an IMRaD* report presents and discusses the main findings of the study. In the results section, writers systematically report their findings, and in discussion, they interpret these findings. (PDF) How to Write an Effective Discussion The discussion section, a systematic critical appraisal of results, is a key part of a research paper, wherein the authors define, critically examine, describe and interpret their findings ... How to Write an Effective Discussion in a Research Paper; a Guide to Discussion is mainly the section in a research paper that makes the readers understand the exact meaning of the results achieved in a study by exploring the significant points of the research, its ... PDF Results and Discussion limitations of your sample, consider how your results might differ with different cultures or other demographic categories (age, gender, ethnicity). Future Directions Another important section of the discussion is speculation about what research questions remain and what research might help to answer those questions. You can sometimes Research Guides: Writing a Scientific Paper: DISCUSSION Papers that are submitted to a journal for publication are sent out to several scientists (peers) who look carefully at the paper to see if it is "good science". These reviewers then recommend to the editor of a journal whether or not a paper should be published. Most journals have publication guidelines. Ask for them and follow them exactly. Research Guides: Writing a Scientific Paper: RESULTS Chris A. Mack. SPIE. 2018. Present the results of the paper, in logical order, using tables and graphs as necessary. Explain the results and show how they help to answer the research questions posed in the Introduction. Evidence does not explain itself; the results must be presented and then explained. Avoid: presenting results that are never ... How to Write a Discussion Section for a Research Paper Begin the Discussion section by restating your statement of the problem and briefly summarizing the major results. Do not simply repeat your findings. Rather, try to create a concise statement of the main results that directly answer the central research question that you stated in the Introduction section. Discussion Section of a Research Paper: Guide & Example The discussion section of a research paper is where the author analyzes and explains the importance of the study's results. It presents the conclusions drawn from the study, compares them to previous research, and addresses any potential limitations or weaknesses. The discussion section should also suggest areas for future research. Discussion Discussion Section. The overall purpose of a research paper's discussion section is to evaluate and interpret results, while explaining both the implications and limitations of your findings. Per APA (2020) guidelines, this section requires you to "examine, interpret, and qualify the results and draw inferences and conclusions from them ... How to Write a Discussion Section What not to include in your discussion section. Step 1: Summarise your key findings. Step 2: Give your interpretations. Step 3: Discuss the implications. Step 4: Acknowledge the limitations. Step 5: Share your recommendations. Discussion section example. PDF Science Writing 101: Distinguishing between Results and Discussion Tips for Writing the Discussion Section. Start with the big picture - WHY is your study important? o Think of yourself as telling the story of how your findings answer the question you posed and why your findings matter, how your field's status quo or understanding is changed by your results. o Clearly signal that you are answering the ... Pharmacological and behavioral investigation of putative self Wild chimpanzees consume a variety of plants to meet their dietary needs and maintain wellbeing. While some plants have obvious value, others are nutritionally poor and/or contain bioactive toxins which make ingestion costly. In some cases, these nutrient-poor resources are speculated to be medicinal, thought to help individuals combat illness. In this study, we observed two habituated ... The Blood Microbiome Is Probably Not Real Last year, results from what purports to be the largest study ever into the question of whether the blood microbiome exists were published in Nature Microbiology. ... But given the incentives of modern research and the social-media spotlight cast on the academic literature, there are two slightly worrying angles here that merit discussion ... (IUCr) Factors affecting macromolecule orientations in thin films 2.3. Grid screening and data collection. Grids were screened on a Titan Krios microscope operating at 300 kV using standard low-dose settings, and automated data collection was set up either on a Falcon 3 or Gatan K2 detector in counting mode with the EPU software (Thermo Fisher Scientific). A magnification of 59 000× was only used for the catalase 37°C data set, with a pixel size of 1.38 Å ... assignment essay homework paper phd report resume review speech thesis