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Coffee may influence much more than alertness. New research suggests that both caffeinated and decaffeinated coffee can alter the gut microbiome and are associated with changes in stress, mood, cognition, and behavior, offering new insight into the connection between the digestive system and the brain.
Researchers at APC Microbiome Ireland at University College Cork studied the microbiota-gut-brain axis, a two-way communication network involving gut microbes, metabolites, hormones, immune activity, and the nervous system. The study, published in Nature Communications, examined 31 regular coffee drinkers and 31 people who did not normally drink coffee. The findings were reported by University College Cork.
The regular coffee drinkers stopped consuming coffee for two weeks before being randomly given either caffeinated or decaffeinated coffee for another 21 days. Researchers collected stool and urine samples throughout the study and assessed participants’ mood, stress, behavior, physical health, and cognitive performance.
The researchers found that coffee consumption was associated with specific changes in gut bacteria, including Cryptobacterium curtum and several Eggerthella strains. These changes occurred after both caffeinated and decaffeinated coffee was reintroduced, suggesting that caffeine was not responsible for all of coffee’s effects on the microbiome.
Coffee abstinence also produced noticeable changes in the participants’ metabolite profiles. When coffee was reintroduced, many metabolites associated with coffee and its polyphenols increased again. Polyphenols are plant compounds that can interact with gut microbes and influence metabolism.
The effects on the brain and behavior differed depending on the type of coffee. Both caffeinated and decaffeinated coffee were associated with lower perceived stress, depression scores, and impulsivity. Caffeinated coffee was also associated with reduced anxiety and improved attention, while decaffeinated coffee was linked to improvements in memory, sleep quality, and physical activity.
However, the researchers caution that the study was relatively small and does not prove that coffee directly causes improvements in mental or cognitive health. Some of the observed changes could also reflect other factors, including behavioral changes during the study.
Professor John Cryan, the study’s corresponding author, said the findings show that coffee is more than a source of caffeine and can interact with gut microbes, metabolism, and emotional well-being.
The results suggest that coffee’s biological effects may come from a combination of caffeine and other compounds, including polyphenols. Larger studies will be needed to determine whether the microbiome changes observed here translate into meaningful long-term health effects.
