Study Reveals Coffee Alters Gut Microbiome and Mood with Benefits from Both Caffeinated and Decaf

A study published this week in Nature Communications explores how regular coffee consumption influences the gut-brain axis, revealing changes in microbiome composition, reduced inflammation, and effects on mood and behavior. Wired reported that scientists at APC Microbiome Ireland compared 31 healthy adults who regularly consume coffee with 31 non-coffee drinkers, detecting alterations in bacteria such as Eggerthella species and Cryptobacterium curtum among drinkers.

These bacteria contribute to gastric and intestinal acid secretion, bile acid synthesis, and the elimination of harmful intestinal bacteria to prevent infections.

John Cryan, a coauthor of the study and principal investigator at APC Microbiome Ireland, a research center at the University of Cork, stated in a press release, 'Coffee is more than just caffeine; it’s a complex dietary factor that interacts with our gut microbes, our metabolism, and even our emotional well-being.

The study analyzed effects when coffee consumers suspended intake for two weeks, noting decreases in impulsiveness and emotional reactivity, along with initial symptoms like fatigue or headache. Regular coffee drinkers showed higher levels of impulsiveness and emotional reactivity compared to non-coffee drinkers.

Researchers then examined resumption of intake for two weeks with either caffeinated or decaffeinated coffee. Both types reduced perceived stress and certain indicators of depression. Caffeinated coffee was associated with improvements in anxiety and some aspects of attention, while decaffeinated coffee showed benefits in memory, sleep quality, and physical activity.

Decaffeinated coffee also induced rapid changes in microbial composition after reintroduction. According to the European Food Safety Authority, a regular coffee drinker consumes between three and five cups a day. Wired reported that coffee consumers presented lower levels of inflammatory markers and higher levels of anti-inflammatory molecules.

During the abstinence period, some markers of inflammation increased. No considerable differences were observed in physiological stress, as measured by the hormone cortisol, between consumers and non-consumers. He added, 'Coffee could modify the activity of microbes as a whole and the metabolites they use.

The study highlights coffee's complex interactions beyond caffeine, with effects on gut microbes and emotional well-being. The research design distinguished caffeine's role from other coffee compounds, such as polyphenols. In regular drinkers, changes in Eggerthella species and Cryptobacterium curtum abundances were detected, favoring microorganisms that support digestive health.

APC Microbiome Ireland explained that these bacteria help prevent infections by eliminating harmful intestinal bacteria. Behavioral findings included higher impulsiveness and emotional reactivity in regular drinkers, which decreased during two weeks of abstinence. Initial abstinence brought symptoms like fatigue or headache in the first days.

Reintroduction of coffee yielded varied benefits: both caffeinated and decaffeinated forms lowered perceived stress and depression indicators.

The study found coffee consumption modifies intestinal microbiome composition, with decaffeinated versions prompting quick microbial shifts. Immune system responses showed coffee drinkers with reduced inflammatory markers and elevated anti-inflammatory molecules.

Physiological stress via cortisol showed no major differences between groups. This story originally appeared on WIRED en Español and has been translated from Spanish.