New research suggests that both regular and decaffeinated coffee can alter the gut microbiome and may influence mood, stress, memory, and attention through the gut brain connection. Scientists at APC Microbiome Ireland, a research center at University College Cork, investigated in detail how coffee may influence communication between the digestive system and the brain. The study published in Nature Communications and sponsored by the Institute for Scientific Information on Coffee (ISIC), found that both caffeinated and decaffeinated coffee were associated with changes in the gut microbiome as well as differences in mood and stress.
How Coffee May Affect the Gut-Brain Connection Scientists have long studied coffee for possible effects on digestion, mood, and overall health, but exactly how these effects arise has remained less clear. The new research focused on the microbiota-gut-brain axis, the two-way communication system linking microorganisms in the digestive tract with the brain. Signals can travel between the gut and brain through immune activity, hormones, nerves, and chemical compounds produced by microbes.
Researchers examined 31 regular coffee drinkers and 31 people who did not normally drink coffee. Participants completed psychological assessments and kept records of caffeine intake and diet. Researchers also collected stool and urine samples to track changes in gut microbes, metabolism, mood, and perceived stress.
For the study, 'Coffee drinkers' were set as those who regularly consume 3-5 cups of coffee a day, defined by the European Food Safety Authority (EFSA) as a safe and moderate amount for most people. The regular coffee drinkers first stopped consuming coffee for two weeks. During that period, participants repeatedly completed psychological assessments and provided stool and urine samples.
When coffee drinkers stopped drinking coffee, researchers observed substantial shifts in their gut metabolite profiles compared with people who did not normally consume coffee. Metabolites are small molecules produced or altered during metabolism, including compounds created by gut microbes as they process food and other substances. Coffee was then reintroduced without participants knowing whether they were receiving caffeinated or decaffeinated coffee.
Half received decaf, while the other half received caffeinated coffee. After coffee returned to their diets, both groups reported lower perceived stress, depression and impulsivity scores. The findings suggest that some of coffee's effects on mood may not depend entirely on caffeine.
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