New research indicates that coffee consumption may impact the trillions of microbes in the gut, which could be associated with mood, stress, and cognition. Conducted by researchers at University College Cork in Ireland, the study published in Nature Communications involved 62 healthy adults aged 30 to 50, divided into two groups: 31 regular coffee drinkers consuming three to five cups daily and 31 non-coffee drinkers.
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The researchers monitored various factors, including mood, cognition, stress, immune function, gut bacteria, and metabolites in stool and urine. Initial findings showed that regular coffee drinkers had significantly different gut microbiomes and displayed greater impulsivity and emotional reactivity, while non-coffee drinkers performed better on memory tests.
Participants who regularly consumed coffee abstained for two weeks and then were randomly assigned to drink either caffeinated or decaffeinated coffee for an additional three weeks. Upon reintroducing coffee, both groups reported reduced perceived stress, depressive symptoms, and impulsivity compared to the end of the abstinence. Those consuming caffeinated coffee reported lower anxiety and psychological distress and improved performance on sustained attention and mental processing tests.
The study also indicated that decaffeinated coffee produced differing effects, suggesting that compounds beyond caffeine influence the brain and body. Changes in the gut microbiome and concentrations of various metabolites were noted when coffee was removed and then reintroduced. Some microbial alterations occurred in both coffee groups, indicating that caffeine alone may not account for all observed effects.
The researchers identified changes in specific bacterial species, including Cryptobacterium curtum and several Eggerthella species, and established links among certain gut microbes, coffee-related metabolites, and cognition. John Cryan, Ph.D., corresponding author of the study, emphasized that these findings provide insight into the complex interplay between coffee, gut microbes, and the brain, and suggest possible long-term benefits for gut health.
Cryan noted, "Coffee is more than just caffeine — it's a complex dietary factor that interacts with our gut microbes, our metabolism, and even our emotional wellbeing." While the study's small scale means the results do not confirm direct causation, they offer new perspectives on how coffee might support health beyond its caffeine content.