Polyphenols improve non-alcoholic fatty liver disease via gut microbiota: A comprehensive review

Polyphenols, natural micronutrients derived from plants, are valued for their anti-inflammatory and antioxidant properties. The escalating global prevalence of non-alcoholic fatty liver disease (NAFLD) underscores its status as a chronic progressive liver condition. Furthermore, the dysregulation of gut microbiota (GM) is implicated in the onset and progression of NAFLD through the actions of metabolites such as bile acids (BAs), lipopolysaccharide (LPS), choline, and short-chain fatty acids (SCFAs). Additionally, GM may influence the integrity of the intestinal barrier. This review aims to evaluate the potential effects of polyphenols on GM and intestinal barrier function, and their subsequent impact on NAFLD. We searched through a wide range of databases, such as Web of Science, PubMed, EMBASE, and Scopus to gather information for our non-systematic review of English literature. GM functions and composition can be regulated by polyphenols such as chlorogenic acid, curcumin, green tea catechins, naringenin, quercetin, resveratrol, and sulforaphane. Regulating GM composition improves NAFLD by alleviating inflammation, liver fat accumulation, and liver enzymes. Furthermore, it improves serum lipid profile and gut barrier integrity. All of these components affect NAFLD through the metabolites of GM, including SCFAs, choline, LPS, and BAs. Current evidence indicates that chlorogenic acid, resveratrol, quercetin, and curcumin can modulate GM, improving intestinal barrier integrity and positively impacting NAFLD. More studies are necessary to evaluate the safety and efficacy of naringenin, sulforaphane, and catechin.