APC Microbiome Ireland study links coffee to gut-brain axis modulation and mood regulation
Scientists find that regular consumption alters bacterial abundance and lowers inflammation, with decaffeinated varieties offering unique advantages for memory and sleep.
Researchers at APC Microbiome Ireland have published findings in Nature Communications indicating that regular coffee consumption significantly alters the human intestinal microbiome, reduces inflammation, and modulates mood through the gut-brain axis. The study, which distinguishes between the effects of caffeinated and decaffeinated varieties, suggests that many health benefits derive from bioactive compounds like polyphenols rather than caffeine alone.
The investigation compared 31 healthy adults who regularly consume coffee with 31 non-coffee drinkers. According to the European Food Safety Authority, a regular drinker is defined as someone consuming between three and five cups a day, a range considered safe and moderate. The team also analysed the effects of suspending intake for two weeks before resuming with either caffeinated or decaffeinated coffee to isolate specific variables.
One of the most relevant findings was that coffee consumption modifies the composition of the intestinal microbiome. In regular drinkers, changes were detected in the abundance of certain bacteria, such as Eggerthella species and Cryptobacterium curtum. These microorganisms are believed to contribute to gastric and intestinal acid secretion, bile acid synthesis, and the elimination of harmful intestinal bacteria, thereby preventing infections.
On the behavioural level, the study found that regular coffee drinkers showed higher levels of impulsiveness and emotional reactivity compared to those who do not partake. However, when coffee intake was suspended for two weeks, these traits decreased. Reintroduction of coffee produced different effects depending on the type, with both caffeinated and decaffeinated options reducing perceived stress and certain indicators of depression.
While caffeinated coffee was associated with improvements in anxiety and some aspects of attention, decaffeinated coffee showed benefits in memory, sleep quality, and physical activity. This indicates that many effects of coffee do not depend exclusively on caffeine but on other bioactive compounds, such as polyphenols, which interact with gut microbes and metabolism.
Another relevant aspect was the response of the immune system. Coffee consumers presented lower levels of inflammatory markers and higher levels of anti-inflammatory molecules compared to non-consumers. During the period of abstinence, some markers of inflammation increased, suggesting that coffee may have a protective effect in this area.
No considerable differences were observed between consumers and non-consumers when it came to physiological stress, as measured by the hormone cortisol. This suggests that, at least under normal conditions, coffee does not substantially alter the body's response to stress, although it may influence the subjective perception of stress. A particularly interesting finding was that some effects on the microbiome occur independently of caffeine, reinforcing the idea that coffee is a complex mixture of compounds with multiple biological effects.
