Background and aim Possible Hepato-protective effects of L-carnitine have been reported in previous studies. Present study was conducted to systematically review the efficacy of L-carnitine supplementation on liver enzymes.

Methods The following databases were searched up to December 2018: PubMed, Scopus, ISI Web of Science, and the Cochrane library. Only randomized controlled trials (RCTs) evaluating the effects of L-carnitine supplementation on liver enzymes including alanine aminotransferase (ALT), aspartate aminotransferase (AST) and gamma-glutamyl transferase (GGT) were included. Pooled effect size measured using random effect model (Dersimonian-Liard).

Results A total of 16 studies (including 1025 participants) were included in the present meta-analysis. Pooled analysis indicated that L-carnitine supplementation significantly decreased ALT (weighted mean difference (WMD): −10.729 IU/L, 95% CI: −13.787, −7.672, p <0.001; I2 = 95.9%), AST (WMD: −7.149 IU/L, 95% CI: −9.202, −5.096, p <0.001; I2 = 93.5%) and GGT (WMD: −7.395: IU/L, 95% CI: −9.171, −5.619, p <0.001; I2 = 80.1%). Subgroup analysis revealed that effect of L-carnitine supplementation on liver enzymes was not significant in normal weight and healthy subjects. Baseline BMI and health status were the potential source of heterogeneity.