Alcohol use alters the colonic mucosa–associated gut microbiota in humans

Alcohol misuse is a risk factor for many adverse health outcomes. Alcohol misuse has been associated with an imbalance of gut microbiota in preclinical models and alcoholic diseases. We hypothesized that daily alcohol use would change the community composition and structure of the human colonic gut microbiota. Thirty-four polyp-free individuals donated 97 snap-frozen colonic biopsies. Microbial DNA was sequenced for the 16S ribosomal RNA gene hypervariable region 4. The SILVA database was used for operational taxonomic unit classification. Alcohol use was assessed using a food frequency questionnaire. We compared the biodiversity and relative abundance of the taxa among never drinkers (ND, n = 9), former drinkers (FD, n = 10), current light drinkers (LD, <2 drinks daily, n = 9), and current heavy drinkers (HD, ≥2 drinks daily, n = 6). False discovery rate–adjusted P values (q values) < .05 indicated statistical significance. HD had the lowest α diversity (Shannon index q value < 0.001), and HD's microbial composition differed the most from the other groups (P value = .002). LD had the highest relative abundance of Akkermansia (q values < 0.001). HD had the lowest relative abundance of Subdoligranulum, Roseburia, and Lachnospiraceaeunc91005 but the highest relative abundance of Lachnospiraceaeunc8895 (all q values < 0.05). The multivariable negative binomial regression model supported these observations. ND and FD had a similar microbial profile. Heavy alcohol use was associated with impaired gut microbiota that may partially mediate its effect on health outcomes.