Coffee Reshapes Gut Bacteria and Mood, Study Finds — SkimNews
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- APC Microbiome Ireland at University College Cork published a Nature Communications study on coffee's effect on the gut-brain axis, comparing 31 regular coffee drinkers (3-5 cups/day) and 31 non-drinkers, with coffee drinkers first abstaining for two weeks before blinded reintroduction of caffeinated or decaf coffee.
- Both caffeinated and decaffeinated coffee groups reported lower perceived stress, depression, and impulsivity scores after reintroduction, suggesting coffee's mood effects do not depend entirely on caffeine.
- Decaffeinated coffee was uniquely linked to improved learning and memory, with researchers pointing to polyphenols and other non-caffeine compounds as the likely drivers of this cognitive effect.
- Caffeinated coffee was associated with reduced anxiety, improved vigilance and attention, and a reduced risk of inflammation.
- Coffee drinkers showed higher levels of gut bacteria including 'Eggertella sp.' (linked to stomach and intestinal acid secretion) and 'Cryptobacterium curtum' (linked to bile acid production), plus elevated Firmicutes bacteria previously tied to positive emotions in females.
- Professor John Cryan, corresponding author and Principal Investigator at APC Microbiome Ireland, said coffee is "more than just caffeine — it's a complex dietary factor that interacts with our gut microbes, our metabolism, and even our emotional well-being."
- The study was sponsored by the Institute for Scientific Information on Coffee (ISIC) and involved a small sample of 62 participants, with researchers noting the findings do not establish that coffee directly causes these mood, cognitive, or gut changes.
Why it matters: The study offers one of the first mechanistic looks at how the beverage reshapes gut microbes and metabolites to influence mood and brain function — most strikingly that decaf, not regular coffee, drove the memory gains, a nuance the 'coffee is good for you' framing often flattens. With gut-health products now a major consumer category, coffee is being repositioned as a potential dietary intervention, though the ISIC sponsorship and 62-person sample mean the findings are directional rather than definitive.
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