Efficacy of Probiotic Treatment in Alcoholic Liver Disease: A Systematic Review of Animal Studies

Alcohol-associated liver disease (ALD) is a major cause of chronic liver injury, in which disruption of the gut-liver axis plays a key pathogenic role. Probiotics have been proposed as a potential therapeutic strategy to mitigate alcohol-induced liver damage; however, the preclinical evidence has not been systematically synthesised. This systematic review aimed to evaluate and summarise the hepatoprotective effects of probiotic supplementation in experimental animal models of ALD.

The review protocol was pre-registered in PROSPERO (CRD420250653666) and followed PRISMA guidelines. A systematic search was conducted across PubMed, EMBASE and AGRICOLA databases using relevant keywords from inception to 30 April 2025. We included preclinical randomised controlled trials evaluating single-strain probiotic interventions against placebo or untreated controls in animal models of ALD. Risk of bias was assessed using SYRCLE's tool, and the certainty of evidence for critical outcomes was evaluated using the GRADE framework. A narrative synthesis was performed, as a quantitative meta-analysis was precluded by incomplete numerical outcome reporting.

From initial 628 records, 36 studies were included in the final synthesis. Probiotic supplementation consistently attenuated alcohol-induced liver injury, as evidenced by marked reductions in serum ALT and AST levels and improved liver histology. Mechanistically, probiotics restored gut barrier integrity, reduced systemic endotoxemia, and suppressed pro-inflammatory pathways. Furthermore, probiotic treatment effectively counteracted alcohol-induced gut dysbiosis by increasing microbial diversity and restoring taxonomic balance, notably by reversing the alcohol-induced expansion of Proteobacteria. Despite these consistent directional effects, the overall certainty of evidence for the critical outcomes was rated as very low.

Although the preclinical literature suggests hepatoprotective effects of probiotics in experimental ALD, these findings should be interpreted with caution due to the very low certainty of evidence. The observed benefits are limited by methodological shortcomings, indirectness inherent to animal models, and incomplete outcome reporting. This review provides a structured preclinical framework to inform the design of future translational studies and well-controlled clinical trials evaluating probiotics as potential adjunctive therapies in human ALD.