Effect of Mediterranean diet on liver enzymes: a systematic review and meta-analysis of randomised controlled trials.

Elevated levels of liver enzymes are the main markers of liver dysfunction. Liver enzymes are the important indicators of non-alcoholic fatty liver disease (NAFLD) in the general population. Previous randomised clinical trials (RCT) investigated the effects of Mediterranean diet (MedDiet) as a plant-based diet on features of NAFLD like liver enzymes, but their results are contradictory. This study aimed to systematically review and meta-analyse RCT investigating the effect of MedDiet on liver enzymes. PubMed, Web of Science, Scopus and Google Scholar were searched until December 2020. A total of ten RCT (n 705 participants) evaluating the effect of MedDiet on liver enzymes including aspartate aminotransferase (AST), alanine transaminase (ALT) and γ-glutamyltransferase (GGT) were included. A random effects model was used to estimate the pooled effect size. To evaluate the heterogeneity among the included studies, the Cochran's Q-test and I-squared test were used. The MedDiet significantly reduced AST (weighted mean difference (WMD) = -0·38 IU/l; 95 % CI - 0·73, -0·03 IU/l; P = 0·03) and GGT (WMD = -0·16 IU/l; 95 % CI - 0·32, -0·006 IU/l; P = 0·04) but had no significant effect on ALT (WMD = -0·55 IU/l; 95 % CI - 1·25, 0·13 IU/l; P = 0·11). However, sensitivity analysis revealed that the overall effects of MedDiet on AST, GGT and ALT were significantly influenced by removing some studies. There was no publication bias based on Begg's and Egger's tests. Generally, MedDiet can improve liver enzymes. To better conclusion, further RCT investigating the effect of MedDiet on liver enzymes, especially in patients with NAFLD, are still required.