New research explores the mechanisms behind coffee’s effects on the gut-brain axis for the first time, linking the popular drink to positive effects on learning, memory, mood and stress.
The study, published in Nature Communications, examined 31 coffee drinkers and 31 non-coffee drinkers through a series of psychological tests, caffeine and food diaries, and stool and urine samples to understand changes in their microbiome and perceived mood or stress. (“Coffee drinkers” defined as those who regularly consume 3-5 cups a day.)
Participants first abstained from coffee for two weeks, with regular psychological assessments, as well as stool and urine samples throughout. This period of abstinence corresponded with significant changes in metabolite profiles in the gut microbiome, compared with non-coffee drinkers.
Coffee was reintroduced to regular drinkers on a blinded basis, with half of participants consuming decaffeinated coffee and the other half regular caffeinated coffee. Both groups reported lower perceived stress, depression and impulsivity scores, suggesting that drinking coffee significantly improved mood, regardless of caffeine content.
The researchers found that some bacteria were increased in coffee drinkers compared with non-coffee drinkers. The former is thought to contribute to gastric and intestinal acid secretion, while the latter is thought to be involved in bile acid synthesis—both of which may play a role in eliminating unhealthy gut bacteria and stomach infections. Increased firmicutes’ bacteria were also observed, which has previously been associated with positive emotions.
A notable improvement in learning and memory was found only in those who consumed decaffeinated coffee, suggesting that components other than caffeine—such as polyphenols—are responsible for these cognitive benefits. However, in this study the researchers found that only caffeinated coffee was associated with reduced feelings of anxiety, as well as improved attention. Caffeine was also linked to reduced risk of inflammation.
Data from APC Microbiome/University College Cork