Across 12 studies spanning humans and non-human primates, alcohol exposure consistently disrupted several gut microbiota-derived metabolic pathways. Short-chain fatty acids — particularly butyrate — were repeatedly reduced, alongside alterations in tryptophan-derived metabolites, hippuric acid (a phenolic compound tied to colonic fermentation), bile acid profiles, and purine metabolism. Faecalibacterium prausnitzii and related butyrate-producing taxa showed reduced abundance across multiple cohorts. Critically, partial recovery of both microbial composition and metabolomic profiles was observed following abstinence.
This review consolidates a mechanistically coherent picture: alcohol systematically erodes the microbial machinery that produces anti-inflammatory short-chain fatty acids while simultaneously disturbing serotonin-pathway precursors via tryptophan metabolism — a dual hit with implications for gut barrier integrity, neuroinflammation, and mood dysregulation. The butyrate-Faecalibacterium connection is especially well-established in IBD research, making its appearance here translatable and credible. Hippuric acid changes are a subtler but intriguing signal, potentially reflecting shifts in polyphenol metabolism. The abstinence-recovery finding is practically important: it suggests these disruptions are not irreversible, supporting gut microbiome restoration as a legitimate target in alcohol use disorder treatment. Limitations are substantial — only 12 studies qualified, heterogeneity in alcohol exposure definitions was high, and causality cannot be established from observational designs. This is confirmatory and clarifying rather than paradigm-shifting, but the candidate biomarker framework it establishes meaningfully advances the translational agenda.