Impact of alcohol on gut microbial metabolism and the gut-liver-brain axis.

The gut microbiome includes a large and diverse microbial community that plays a central role in host health, supported by an extensive genomic repertoire that is distinct from and complementary to mammalian enzymatic pathways. Alcohol consumption disrupts this ecosystem, inducing microbial dysbiosis and altering functional interactions between the host and its gut bacteria that can lead to systemic effects. In this review, we examine how alcohol affects gut bacteria, and how these changes impair essential bacterial functions, including short-chain fatty acid production, mucin metabolism, biofilm formation, and bile acid metabolism, that support intestinal, liver, and brain health. We further describe how certain gut bacteria tolerate or produce ethanol, and how these traits contribute to the systemic harms associated with alcohol-induced dysbiosis. Finally, we highlight therapeutic strategies aimed at targeting ethanol-tolerant or ethanol-producing bacteria as potential avenues for preventing or mitigating intestinal inflammation, liver injury, and other metabolic disorders.