The effect of melatonin supplementation on liver indices in patients with non-alcoholic fatty liver disease: A systematic review and meta-analysis of randomized clinical trials

Several randomized clinical trials (RCTs) evaluated the effect of melatonin supplementation on liver enzymes in patients with non-alcoholic fatty liver disease (NAFLD) and reported conflicting results. To meet these discrepancies, a meta-analysis was conducted to evaluate the effect of melatonin on liver indices in patients with NAFLD. To collect the required data, a thorough search was conducted through Web of science, Pubmed, Cochrane database, Embase, Google Scholar, ProQuest, and Scopus databases. The aim was to find clinical trials over the effect of melatonin supplementation on liver indices up to 16 May 2019. As a result, five eligible articles were selected and analysed in this meta-analysis using a fixed-effects model. Heterogeneity test was performed by 1 2 statistics and Cochrane Q test. The results showed that melatonin had a significant effect on aspartate aminoteransferase (AST) (WMD = 2.29, [95 %CI: 1.14, 3.43] IU/L, p = <0.001), alkaline phosphatase (ALP) (WMD = -8.40, [95 %CI - 11.33, -5.48] IU/L, p < 0.001), and gamma-glutamyltransferase (GGT) (WMD = - 33.37, [95 %CI: - 37.24, - 29.49] IU/L, p = < 0.001). Melatonin had no significant effect on alanine aminotransferase (ALT) regarding the overall effect size. Based on this meta-analysis, melatonin supplementation can improve liver indices. However, more RCTs are required with larger sample sizes and better control of confounding variables such as weight, body mass index, and gender to determine the effect of melatonin on patients with non-alcoholic fatty acid disease.