Effects of carnitine supplementation on liver aminotransferase enzymes: A systematic review and meta-analysis of randomized controlled clinical trials.

Abstract

This meta-analysis of the randomized controlled trials was performed to assess effects of carnitine supplementation on serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) levels. A comprehensive literature search of PubMed, Cochrane's library, Web of Science, Scopus, and Embase was performed up to May 2018. From a total of 2012 articles identified initially, only 17 articles were included in the final meta-analysis to evaluate the effects of carnitine supplementation on serum levels of ALT and AST enzymes. Random effects model meta-analysis showed that carnitine supplementation led to reduction in serum ALT (weighted mean difference [WMD] - 10.25IU/L; 95% CI = - 15.73, - 4.77; p < 0.001) and AST levels (WMD - 7.85IU/L; 95% CI = - 11.85, - 3.86; p < 0.001). The results of subgroup analysis showed that carnitine could reduce serum AST levels at dosages equal to 2000mg/day (p = 0.014) or more than 2000mg/day (p < 0.001). However, carnitine supplementation at dosages of ≤ 1000mg/day (p = 0.035) or equal to 2000mg/day (p = 0.013) resulted in significant reduction in ALT level, while doses more than 2000mg/day did not change ALT significantly. Carnitine exerts its reducing effect on serum ALT and AST levels only when these aminotransferases are raised or when the duration of supplementation lasts at least 3months. Results of the current meta-analysis showed that carnitine supplementation can decrease serum AST and ALT levels significantly, especially when supplementation lasts 3months or more in patients with elevated serum aminotransferase levels.