Coffee, including decaf, linked to better mood, gut health, brain function

Coffee may be doing more than delivering a jolt. In a 62-person study, both regular and decaf coffee were linked to lower perceived stress, depression and impulsivity, while decaf also tracked with better learning and memory.

Researchers at APC Microbiome Ireland at University College Cork compared 31 coffee drinkers with 31 non-coffee drinkers to test the microbiota-gut-brain axis and whether coffee’s effects depended on caffeine. The coffee drinkers regularly consumed 3 to 5 cups a day, a range the European Food Safety Authority describes as safe and moderate for most people. Before coffee was reintroduced, participants abstained for two weeks. They completed psychological testing, kept caffeine and food diaries, and provided stool and urine samples.

Coffee then came back in a blinded design, with some participants receiving caffeinated coffee and others decaffeinated coffee. The results, published in Nature Communications, point to an effect that reaches beyond caffeine alone. Both forms of coffee were associated with lower stress, depression and impulsivity scores. Decaf was linked to improved learning and memory, suggesting that compounds other than caffeine, including polyphenols, may help drive at least some of the brain-related changes.

The gut findings were just as notable. Coffee drinkers showed increased relative abundance of Cryptobacterium and Eggerthella species, along with reduced levels of indole-3-propionic acid, indole-3-carboxyaldehyde and gamma-aminobutyric acid. An integrated model identified nine key metabolites tied to microbial species and cognitive measures, giving researchers a more detailed picture of how coffee may influence mood and brain function through the gut.

The study is an important step, but it is still an early one. It involved a small sample, followed people only through a short withdrawal and reintroduction period, and did not prove that coffee improves long-term health outcomes or that the same effects will appear in every group. University College Cork said the project was its first comprehensive look at coffee’s positive effects on the gut-brain axis. The work was sponsored by the Institute for Scientific Information on Coffee, and it adds to a broader body of evidence suggesting regular coffee, including decaf, may affect the body in ways caffeine alone cannot explain.