Ethanol-Induced Dysbiosis and Systemic Impact: A Meta-Analytical Synthesis of Human and Animal Research

Background: Chronic ethanol consumption is a major global health concern traditionally associated with liver disease. Ethanol disrupts gut microbial communities, compromises intestinal barrier function, and contributes to hepatic, metabolic, and neurocognitive disorders. Methods: We conducted a systematic PubMed search and meta-analysis of 11 human and 19 animal studies evaluating ethanol-induced gut microbiota alterations. Studies were assessed for microbial diversity, taxonomic shifts, barrier integrity, and systemic effects. Effect sizes were calculated where possible, and interventional outcomes were examined. Results: Across species, ethanol exposure was consistently associated with reduced microbial diversity and depletion of beneficial commensals such as Faecalibacterium, Lactobacillus, Akkermansia, and Bifidobacterium, alongside an expansion of proinflammatory taxa (Proteobacteria, Enterococcus, Veillonella). Our analysis uniquely highlights discrepancies between human and animal studies, including opposite trends in specific genera (e.g., Akkermansia and Bifidobacterium) and the impact of confounders such as antibiotic exposure in human cohorts. We also demonstrate that microbiota-targeted interventions can partially restore diversity and improve clinical or behavioral outcomes. Conclusions: This meta-analysis highlights reproducible patterns of ethanol-induced gut dysbiosis across both human and animal studies.