Mediterranean diet for patients with non-alcoholic fatty liver disease, a systematic review and meta-analysis of observational and clinical investigations

Aim Mediterranean diet (MD) is a healthful dietary pattern with benefits for prevention of metabolic diseases including non-alcoholic fatty liver disease (NAFLD). In the current meta-analysis, we assessed the association between MD and liver steatosis and cardiometabolic risk factors in patients with NAFLD. Methods PubMed, Scopus, and Embase were searched to find observational and clinical studies on the issue. No restriction on date and language was made. Outcomes included body mass index (BMI), waist circumference, blood pressure, triglycerides (TG), cholesterol fractions, glucose, insulin, insulin resistance, and liver transaminases. Results Seven observational reports and 6 trials met our inclusion criteria and entered in the meta-analysis. In observational studies, there was an inverse association between MD and NAFLD (effect size (ES) = 0.95; 95% CI: 0.90, 1.00; P = 0.05). In trials, subgroup analysis based on the method of liver examination showed effectiveness of MD on steatosis examined by magnetic resonance spectroscopy (P < 0.002; n = 2) but not by ultrasound (P = 0.08; n = 2). MD also showed a significant decreasing effect on BMI (ES = -1.23 kg/m(2); 95% CI: -2.38, -0.09), plasma triglycerides (ES = -33.01 mg/dL; 95% CI: -52.84, -13.18), and HOMA-IR (ES = -0.94; 95% CI: -1.29, -0.58) but no significant effect was observed in waist circumference, cholesterol fractions, glucose and insulin, and liver transferases. Conclusion Overall, available data from observational and clinical studies indicated a trend for the relationship between MD and hepatic steatosis. Improvement in the most important risk factors of NAFLD, i.e. BMI, serum triglycerides, and insulin resistance, may be involved in such relationship.