The effect of l-carnitine supplementation on lipid profile and glycaemic control in adults with cardiovascular risk factors: A systematic review and meta-analysis of randomized controlled clinical trials

Summary Background & aims Several randomized clinical trials (RCTs) have investigated the effect of l -carnitine supplementation on lipid profile and glycaemic control in adults with cardiovascular risk factors; however, the results were conflicting. Therefore, a meta-analysis was performed to assess the effect of l -carnitine on lipid profile and glycaemic control in adults with cardiovascular risk factors. Methods We searched PubMed, Scopus, Cochrane Databases, Google Scholar, ProQuest, Web of Science and Embase for randomized, placebo-controlled human trials that investigated the effect of l -carnitine supplementation on lipid profile and glycaemic control up to April 2017. From the eligible trials, 24 articles were selected for the meta-analysis. The meta-analysis was performed in a random-effects model. Heterogeneity was determined by I 2 statistics and Cochrane Q test. Results The result showed significant effect of l -carnitine on TC (WMD: −13.73 [95% CI: −22.28, −5.17] mg/dL; P   0.001), Lp(a) (WMD = − 7.13 [95% CI: −9.82,− 4.43]mg/dL; P  l -carnitine was detected in TG, Apo A-I and Apo B 100 on pooled effect size. Additionally, sensitivity analysis showed l -carnitine supplementation could improve glycaemic control, particularly along with hypocaloric diet. Conclusion This meta-analysis showed that l -carnitine supplementation could improve lipid profile levels, particularly in doses more than 1500 mg/day. More RCTs with large sample sizes, focusing on gut microbiome profiles and dietary patterns are needed to better understand the effect of l -carnitine on patients with cardiovascular risk factors.