Beyond Caffeine: How Coffee Enhances Gut Health and Brain Function

New research from APC Microbiome Ireland at University College Cork reveals that both caffeinated and decaffeinated coffee actively reshape the gut microbiome in ways that influence mood, stress and cognitive function. The study, published in Nature Communications on April 21, 2026, is the first to comprehensively explore the mechanisms behind coffee’s effects on the gut-brain axis—the bidirectional communication between the gut microbiome and the brain.

The research involved 62 healthy adults aged 30 to 50, including both habitual coffee drinkers (consuming 3 to 5 cups daily) and non-coffee drinkers. Participants underwent psychological assessments, provided stool and urine samples, and were monitored during periods of coffee abstinence and reintroduction—with some receiving caffeinated coffee and others decaffeinated.

Key findings include:

• Mood and Stress: Both caffeinated and decaffeinated coffee were associated with reduced perceived stress, depression, and impulsivity. Coffee drinkers reported improved mood, regardless of caffeine content.
• Cognitive Function: Decaffeinated coffee improved learning and memory, while caffeinated coffee enhanced vigilance, attention, and reduced anxiety. These effects suggest that different compounds in coffee—caffeine and polyphenols—play distinct roles in brain function.
• Gut Microbiome: Coffee consumption altered the gut microbiome, increasing beneficial bacteria such as Eggerthella sp and Cryptobacterium curtum, which are linked to improved digestion and elimination of harmful bacteria. The study also found increased levels of Firmicutes, a bacterial group associated with positive emotions in females.
• Metabolite Changes: Coffee abstinence and reintroduction led to reversible changes in gut metabolites, including indole-3-propionic acid and neurotransmitters like γ-aminobutyric acid (GABA). These changes were linked to cognitive and emotional outcomes.

Professor John Cryan, Principal Investigator at APC Microbiome Ireland, emphasized the significance of these findings:

“The relationship between digestive and mental health is increasingly understood, but the mechanisms behind coffee’s effects on this gut-brain axis have remained unclear. Our findings reveal the microbiome and neurological responses to coffee, as well as their potential long-term benefits for a healthier microbiome.”

Professor John Cryan, APC Microbiome Ireland

The study also highlights that coffee’s benefits extend beyond caffeine. While caffeine was linked to reduced anxiety and improved focus, decaffeinated coffee showed unique cognitive benefits, suggesting that other compounds—such as polyphenols—play a crucial role in enhancing learning and memory.

This research builds on previous studies linking coffee consumption to reduced risks of type 2 diabetes, cardiovascular disease, Parkinson’s disease, depression, and cognitive decline. The findings suggest that coffee’s impact on the gut microbiome may be a key mechanism behind these broader health benefits.

However, the study also notes that individual responses to coffee may vary, and further research is needed to fully understand the long-term effects and potential personalized approaches to coffee consumption for optimal gut and brain health.

For now, the research underscores coffee’s potential as a dietary tool for supporting both digestive and mental well-being, offering a deeper understanding of how this everyday beverage influences our bodies and minds.