Is coffee actually good for you?
Some experts tout its health benefits, such as lowering the risk of type 2 diabetes and Alzheimer’s disease. At the same time, excessive caffeine consumption has been linked to various health conditions, such as anxiety, headaches, faster heart rate, and in some cases, lower bone density in women.
Although coffee is widely believed to improve digestion and mood, what is less clear is the mechanism for how this works in the body—namely, its effect on our gut-brain axis, which is the two-way communication system linking microorganisms in the digestive tract to the brain.
To this end, researchers from the University College Cork’s APC Microbiome Ireland studied 31 regular coffee drinkers (who consumed three to five cups of coffee a day) and 31 non-coffee drinkers. They recorded their caffeine intake, diet, and changes to their gut microbes using stool and urine samples.
Then, study participants were prohibited from drinking coffee for two weeks. That’s when researchers found something surprising in the guts of the coffee drinkers: Their metabolites had changed.
After that two-week period, coffee was reintroduced, with half the study receiving regular caffeinated coffee, and the other half decaf. The researchers found both groups, regardless of whether they consumed decaf or caffeinated coffee, exhibited lower stress, depression, and even impulsivity—which means coffee’s benefits extend beyond merely caffeine.
The researchers published their results in the journal Nature Communications. They also found coffee consumption led to measurable changes in the diversity of bacteria and metabolites in the gut: The study’s coffee drinkers exhibited an increase in Cryptobacterium curtum, Eggerthella sp., and Firmicutes bacteria.
The study included 63 healthy Irish adults between the ages of 30 and 50, and took place between September 2021 and January 2023.