62 Adults and the 31 Regular Coffee Drinkers Compared in Gut Microbiome Study
A clinical study published on April 21, 2026, in Nature Communications examined 62 healthy adults to determine how regular coffee consumption affects the human gut microbiome, host physiology, and cognitive performance. Led by researcher Serena Boscaini, the investigation compared 31 habitual coffee consumers with 31 non-consumers, as Mondosanità reported. The participants who regularly drank coffee then suspended their intake for fourteen days before reintroducing the beverage for twenty-one days, splitting into two groups where 15 received decaffeinated coffee and 16 received caffeinated coffee.
Bacteria Shifts Observed in Caffeinated and Decaffeinated Trials
During the two-week coffee elimination phase, researchers observed that various differences in gut bacteria and fecal metabolites among habitual drinkers began to attenuate. When participants resumed drinking coffee, both the caffeinated and decaffeinated versions prompted measurable shifts in specific bacterial populations within the gastrointestinal tract. Further supporting the microbial connection, an earlier study published in November 2024 in Nature Microbiology analyzed microbiome data from more than 22,000 individuals and found that the bacterium Lawsonibacter asaccharolyticus was 4.5 to 8 times more abundant in coffee consumers than in non-consumers.
Cognitive Performance and Behavioral Differences Between Groups
The trial tracked behavioral metrics alongside biological samples, noting that both the caffeinated and decaffeinated groups reported decreased perceived stress, depressive symptoms, and impulsivity scores following reintroduction.
Daily Caffeine Limits and Dietary Guidelines for Consumers
For individuals who experience jitters or sleep disturbances from caffeinated beverages, decaffeinated coffee offers an alternative that still interacts directly with the gut microbiome through non-stimulant plant compounds such as polyphenols. The European Food Safety Authority (EFSA) states in its scientific opinion on caffeine safety that up to 400 milligrams of caffeine per day from all sources generally raises no safety concerns for healthy adults, while pregnant individuals are advised to limit intake to 200 milligrams daily.
Frequently Asked Questions About Coffee and Gut Health
Did the study prove that decaffeinated coffee improves human memory?
No, the study only observed an association between decaffeinated coffee reintroduction and better scores on specific memory and learning tests. Authors note that small sample sizes and potential test-learning effects mean researchers have not established direct causation.
Which specific bacterium thrives most in the gut of coffee drinkers?
Data from Nature Microbiology identified Lawsonibacter asaccharolyticus as being 4.5 to 8 times more abundant in habitual coffee consumers compared to non-consumers, a finding backed by laboratory culture experiments showing direct bacterial growth promotion.
What is the safe daily caffeine limit established by the EFSA?
The European Food Safety Authority sets a safe intake level of up to 400 milligrams of caffeine per day for healthy adults, and 200 milligrams per day for pregnant individuals, based on its comprehensive safety evaluation.
How long did participants stop drinking coffee during the clinical trial?
The 31 habitual coffee consumers in the Nature Communications study suspended their regular coffee intake for exactly fourteen days before reintroducing either caffeinated or decaffeinated versions for twenty-one days.
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