Research finds coffee consumption improves mood and alters gut microbiome — Evidence Review
Published in Nature Communications, by researchers from APC Microbiome Ireland, University College Cork, Institute for Scientific Information on Coffee
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Table of Contents
Coffee consumption—both caffeinated and decaffeinated—can positively alter gut microbiota and improve mood and cognition, according to a new study from APC Microbiome Ireland. Most related studies generally support these findings, although results regarding cognitive benefits and the specific roles of caffeine and other coffee compounds are mixed; see the original research in Nature Communications.
- Multiple studies confirm that coffee and its components can modulate the gut microbiome, with several reporting increases in beneficial bacteria such as Bifidobacterium spp. and changes linked to coffee polyphenols and caffeine 11 13 14 15.
- Research supports coffee’s positive influence on mood and alertness, though results are less consistent for memory and executive function, with some studies finding that benefits are primarily due to caffeine, while others suggest non-caffeine coffee compounds may also play a role 2 3 5 6 7.
- Some findings suggest decaffeinated coffee does not improve cognition in older adults 4, contrasting with the new study’s evidence that decaf may enhance learning and memory, highlighting the need for further investigation into coffee’s non-caffeine bioactive compounds 7 13 15.
Study Overview and Key Findings
Coffee is a widely consumed beverage, and its health effects—particularly regarding digestion, mood, and cognitive function—are of significant public interest. While the positive impact of coffee on mental alertness and digestion has been recognized anecdotally and in some observational studies, the biological mechanisms underlying these effects have remained unclear. This new study from APC Microbiome Ireland is notable for its detailed examination of the gut-brain axis and its use of both caffeinated and decaffeinated coffee to parse out the roles of different coffee components.
Below is a summary of the study’s key metadata:
| Property | Value |
|---|---|
| Study Year | 2026 |
| Organization | APC Microbiome Ireland, University College Cork, Institute for Scientific Information on Coffee |
| Journal Name | Nature Communications |
| Authors | Serena Boscaini, Thomaz F. S. Bastiaanssen, Gerard M. Moloney, Federica Bergamo, Laila Zeraik, Caroline O’Leary, Aimone Ferri, Maha Irfan, Maaike van der Rhee, Thaïs I. F. Lindemann, Elizabeth Schneider, Arthi Chinna Meyyappan, Kirsten Berding Harold, Caitríona M. Long-Smith, Carina Carbia, Kenneth J. O’Riordan, José Fernando Rinaldi de Alvarenga, Nicole Tosi, Daniele Del Rio, Alice Rosi, Letizia Bresciani, Pedro Mena, Gerard Clarke, John F. Cryan |
| Population | Coffee drinkers and non-coffee drinkers |
| Sample Size | n=62 |
| Methods | Non-randomized Controlled Trial (Non-RCT) |
| Outcome | Gut microbiome changes, mood, stress, cognition |
| Results | Coffee drinkers showed improved mood and gut microbiome changes. |
Literature Review: Related Studies
To situate the new findings within the broader research landscape, we searched the Consensus database, which aggregates findings from over 200 million scientific papers. The following search queries were used to identify relevant studies:
Summary Table of Key Topics and Findings
| Topic | Key Findings |
|---|---|
| How does coffee (and caffeine) affect mood and cognitive performance? | - Caffeine improves alertness, vigilance, and attention, with less consistent effects on memory and executive function 2 5 6. - Both caffeinated and decaffeinated coffee can improve mood; evidence for memory enhancement is mixed, with some studies showing benefits primarily due to caffeine 3 4 7. |
| What effects does coffee have on the gut microbiome? | - Coffee consumption can increase populations of beneficial bacteria such as Bifidobacterium spp. and modulate gut microbiota composition 11 13 14 15. - Coffee polyphenols, including chlorogenic acids, selectively increase growth of specific gut bacteria, potentially benefiting host health 13 15. |
| Are there distinct effects of caffeinated vs. decaffeinated coffee? | - Caffeinated coffee is more consistently linked to improved cognitive performance, while decaffeinated coffee may have more modest or no effects, especially in older adults 4 5 7. - Some studies suggest non-caffeine compounds in coffee may have psychoactive effects, but findings are inconsistent and require further study 7 13. |
| What is the relationship between coffee, inflammation, and mental health? | - Coffee constituents, especially caffeine and certain polyphenols, may reduce inflammation and lower the risk of depression by modulating neuroinflammatory pathways 10. - Moderate caffeine intake is associated with less depressive symptoms, fewer cognitive failures, and lower suicide risk, although high doses may increase anxiety 8 10. |
How does coffee (and caffeine) affect mood and cognitive performance?
The majority of research supports coffee’s positive impact on alertness and mood, largely attributed to caffeine. Cognitive improvements, particularly in memory and learning, are less consistent across studies. While some evidence indicates benefits for long-term memory consolidation after caffeine intake 1, other studies report minimal or no effect on intentional learning or memory tasks 3 5. The new study’s finding that both caffeinated and decaffeinated coffee can improve mood aligns with several previous studies, but its observation of decaf-specific memory benefits diverges from larger epidemiological analyses in older adults 4.
- Caffeine reliably improves alertness, vigilance, and reaction time; effects on memory and executive function are less robust 2 5 6.
- Both habitual consumers and non-consumers of caffeine experience cognitive and mood improvements, but habitual users benefit more in mood, and non-users in performance 6.
- Acute and habitual coffee consumption is generally associated with reduced boredom and improved subjective mood, though high doses can increase anxiety 3 5 8.
- Decaffeinated coffee may also have psychoactive effects, but evidence is inconsistent and requires additional research 7.
What effects does coffee have on the gut microbiome?
Growing evidence suggests coffee consumption can modulate the gut microbiota by increasing populations of beneficial bacteria and altering microbial metabolic activity. The new study’s finding that both caffeinated and decaffeinated coffee shape the gut microbiome and increase levels of certain bacteria is consistent with earlier research showing increases in Bifidobacterium spp. and modulation of other bacterial groups 11 13 14 15. Coffee-derived polyphenols appear to play a significant role in this process, supporting the new study’s focus on non-caffeine compounds.
- Regular coffee intake increases beneficial gut bacteria, notably Bifidobacterium spp., in both human and animal models 11 13 14 15.
- Coffee polyphenols, such as chlorogenic acids, are selectively metabolized by gut bacteria and may promote growth of specific populations 13 15.
- Changes in gut microbiota composition after coffee consumption may contribute to improved gut health and metabolic profiles 11 12 13 15.
- Coffee’s impact on the gut microbiome is observed with both caffeinated and decaffeinated varieties, though the magnitude and specific changes may differ 15.
Are there distinct effects of caffeinated vs. decaffeinated coffee?
Research comparing caffeinated and decaffeinated coffee suggests that caffeine is the primary driver of cognitive benefits, though some studies report psychoactive effects of coffee components beyond caffeine 7. The new study’s finding that decaffeinated coffee improved learning and memory, while caffeinated coffee reduced anxiety and improved alertness, contrasts with previous large-scale studies in older adults that found no cognitive benefit from decaf 4. This suggests potential age or methodological differences and underscores the complexity of coffee’s bioactive compounds.
- Caffeinated coffee consistently improves cognitive measures such as attention, vigilance, and processing speed 2 5 6.
- Decaffeinated coffee is generally less effective for cognitive enhancement, with some studies showing no significant association with cognitive performance in older adults 4.
- Some research highlights potential psychoactive or cognitive benefits of non-caffeine components in coffee, but these effects are variable and need further study 7 13.
- The complex interaction between caffeine, polyphenols, and other coffee constituents may produce distinct effects depending on individual and study characteristics 5 7 13.
What is the relationship between coffee, inflammation, and mental health?
Several reviews and clinical studies indicate that coffee, particularly its caffeine and polyphenol content, may exert anti-inflammatory effects and reduce risk for depression and other mental health conditions 10. The new study’s observation that coffee consumption (regardless of caffeine content) improved mood and reduced markers of stress and depression is consistent with broader findings that moderate coffee intake is associated with better mood and mental health outcomes 8 10. However, higher caffeine doses can increase anxiety in sensitive individuals, highlighting the importance of moderation.
- Coffee consumption, especially caffeinated, is associated with lower risk of depression and improved mental well-being in multiple epidemiological studies 8 10.
- Bioactive constituents in coffee, such as caffeine and chlorogenic acid, modulate neuroinflammatory pathways linked to depression 10.
- Moderate caffeine intake (<6 cups/day) is associated with less depressive symptoms, but high doses may trigger anxiety, especially in sensitive populations 8 10.
- The role of decaffeinated coffee and non-caffeine coffee compounds in mental health remains less clear and requires further research 4 10.
Future Research Questions
Despite advances, several questions remain regarding the mechanisms by which coffee and its components influence the gut-brain axis, cognitive function, and mental health. Future research is needed to clarify the roles of specific coffee compounds, individual variability in response, long-term effects, and the interplay between the gut microbiome and neurological outcomes.
| Research Question | Relevance |
|---|---|
| How do non-caffeine coffee compounds (such as polyphenols) directly affect cognition and mood? | This question addresses the distinct roles of coffee’s non-caffeine bioactive components, which may explain the cognitive and mood effects observed with decaffeinated coffee in the new study. Current research is mixed, with some studies suggesting benefits 7 13, but more evidence is needed to determine mechanisms and efficacy, especially in different age groups 4. |
| What are the long-term effects of regular decaffeinated coffee consumption on the gut microbiome and cognitive health? | There is a knowledge gap regarding the sustained impact of decaffeinated coffee on gut microbiota and cognition, especially as most long-term studies focus on caffeinated coffee 4 15. Understanding these effects is crucial for populations sensitive to caffeine or avoiding it for health reasons. |
| How do individual differences (e.g. age, genetics, baseline microbiome) influence the gut-brain and mental health effects of coffee? | Response to coffee and caffeine varies between individuals, potentially due to genetic factors, baseline gut microbiota, and age 6 8. Investigating these moderators could inform personalized dietary recommendations and help explain conflicting findings in the literature 4 5 6 7. |
| What are the mechanistic pathways by which coffee-induced gut microbiome changes influence neurological outcomes? | While associations between coffee intake, microbiome changes, and cognitive/mood outcomes are observed 11 13 14 15, the underlying biological mechanisms remain largely unelucidated. Elucidating these pathways would advance understanding of the gut-brain axis and inform interventions for mental and digestive health 13 15. |
| Can coffee or its compounds be used as interventions for clinical mental health or neurodegenerative conditions? | Given evidence for coffee’s mood-enhancing and anti-inflammatory properties 8 10, there is interest in its potential as an adjunct or preventive intervention for depression, cognitive decline, or neurodegenerative diseases. However, robust clinical trials are needed to establish efficacy and safety in these populations 10. |