Background: The findings of trials investigating the effects of L-carnitine administration on serum
lipids are inconsistent. This meta-analysis of randomized controlled trials (RCTs) was performed to summarize
the effects of L-carnitine intake on serum lipids in patients and healthy individuals.
Methods: Two authors independently searched electronic databases including MEDLINE, EMBASE, Cochrane
Library, Web of Science, PubMed and Google Scholar from 1990 until August 1, 2019, in order to find relevant
RCTs. The quality of selected RCTs was evaluated using the Cochrane Collaboration risk of bias tool. Cochrane’s
Q test and I-square (I2) statistic were used to determine the heterogeneity across included trials. Weight mean
difference (SMD) and 95% CI between the two intervention groups were used to determine pooled effect sizes.
Subgroup analyses were performed to evaluate the source of heterogeneity based on suspected variables such as,
participant’s health conditions, age, dosage of L-carnitine, duration of study, sample size, and study location
between primary RCTs.
Results: Out of 3460 potential papers selected based on keywords search, 67 studies met the inclusion criteria and
were eligible for the meta-analysis. The pooled results indicated that L-carnitine administration led to a significant
decrease in triglycerides (WMD: -10.35; 95% CI: -16.43, -4.27), total cholesterol (WMD: -9.47; 95% CI: -
13.23, -5.70) and LDL-cholesterol (LDL-C) concentrations (WMD: -6.25; 95% CI: -9.30, -3.21), and a significant
increase in HDL-cholesterol (HDL-C) levels (WMD: 1.39; 95% CI: 0.21, 2.57). L-carnitine supplementation did
not influence VLDL-cholesterol concentrations. When we stratified studies for the predefined factors such as
dosage, and age, no significant effects of the intervention on triglycerides, LDL-C, and HDL-C levels were found.
Conclusion: This meta-analysis demonstrated that L-carnitine administration significantly reduced triglycerides,
total cholesterol and LDL-cholesterol levels, and significantly increased HDL-cholesterol levels in the pooled
analyses, but did not affect VLDL-cholesterol levels; however, these findings were not confirmed in our subgroup
analyses by participant’s health conditions, age, dosage of L-carnitine, duration of study, sample size, and study