Fermented Foods and the Gut–Liver Axis: Modulation of MASLD Through Gut Microbiota

Background/Objectives: Metabolic Dysfunction-Associated Steatotic Liver Disease (MASLD) is a prevalent condition defined by hepatic fat accumulation, inflammation, and metabolic dysregulation. Current evidence demonstrates that gut microbiota and their metabolites are associated with MASLD pathogenesis. Fermented foods, rich in live microbes and bioactive compounds, actively modulate the gut–liver axis and influence disease progression. This narrative review provides a comprehensive summary of current evidence on the impact of fermented foods on gut microbiota, intestinal barrier function, and gut–liver interactions, and demonstrates their potential role in preventing or mitigating MASLD. Methods: A comprehensive literature search of preclinical and clinical studies was conducted. Specifically, the review focused on fermented-food interventions, modulation of gut microbiota, metabolite production, and effects on hepatic metabolism and inflammation. Results: This review found that fermented foods provide probiotics, prebiotics, short-chain fatty acid (SCFAs), and bioactive compounds that enhance microbial diversity, improve intestinal barrier integrity, reduce endotoxemia, and modulate bile acid and lipid metabolism. Evidence from animal and human studies indicates that fermented food consumption can attenuate hepatic steatosis, inflammation, and metabolic dysregulation, with variability depending on individual microbiome composition. Conclusions: Altogether, these findings suggest that fermented foods represent a promising adjunctive dietary strategy for MASLD by modulating the gut–liver axis and supporting metabolic and hepatic health. Personalized approaches and further long-term clinical trials are required to optimize interventions and establish evidence-based recommendations.