The role of probiotics in the treatment of non-alcoholic fatty liver disease (NAFLD): New insights based on meta-analysis and subgroup analysis

Despite numerous studies suggesting a link between probiotics and non-alcoholic fatty liver disease (NAFLD), the effects on clinical outcomes remain contentious. This meta-analysis evaluates probiotic effects on liver enzymes, glycaemic control, lipids, and inflammation in NAFLD patients. Comprehensive searches up to April 2024 in PubMed, Web of Science, Embase, and Cochrane Library were conducted without language restrictions. A random-effects model derived aggregated outcomes, with subgroup analyses for BMI, study location, and intervention duration. Incorporating 33 studies with 1940 participants from 15 countries, significant reductions were observed in ALT (SMD: −0.87, 95% CI: −1.22, −0.53), AST (SMD: −1.10, 95% CI: −1.48, −0.71), fasting blood glucose (SMD: −0.30, 95% CI: −0.49, −0.11), fasting insulin (SMD: −0.64, 95% CI: −1.20, −0.07), HbA1c (SMD: −0.45, 95% CI: −0.85, −0.06), insulin resistance (SMD: −0.35, 95% CI: −0.56, −0.14), total cholesterol (SMD: −0.39, 95% CI: −0.66, −0.11), triglycerides (SMD: −0.27, 95% CI: −0.43, −0.12), low-density lipoprotein cholesterol (SMD: −0.31, 95% CI: −0.52, −0.10), and TNF-α (SMD: −0.99, 95% CI: −1.67, −0.31) compared to controls. Subgroup analyses showed multi-strain or combined probiotics were more effective than single-strain. Efficacy on fasting insulin, total cholesterol, and TNF-α was significantly influenced by BMI and geographic region. Our findings suggest probiotics significantly improve liver enzyme levels, blood lipid profiles, blood glucose control, and inflammatory markers in NAFLD patients. Multi-strain probiotics or combined supplements particularly enhance insulin sensitivity and reduce total cholesterol and TNF-α levels, especially in individuals aged 55 years or younger and those with a baseline BMI below 30 kg/m².