Aim and background: Reducing inflammation by nutritional supplements may help to reduce the risk of many chronic diseases. Our aim in this meta-analysis was to determine the effect of L-carnitine on inflammatory mediators including C-reactive protein (CRP), tumor necrosis factor-α (TNF-α), and interleukin-6 (IL-6).

Methods: Our systematic search to find relevant randomized clinical trials (RCTs) was performed up to October 2018 using ISI Web of Science, Google Scholar, PubMed/Medline, and SCOPUS. In this meta-analysis, the weighted mean differences (WMD) with standard errors (SE) were used to pool the data. WMD was calculated by subtracting change-from-baseline mean values in the control group from change-from-baseline mean values in the intervention group in each study. To identify heterogeneity among studies, the I² statistic was employed. The protocol was registered with PROSPERO (No. CRD42019116695).

Results: Thirteen articles were included in our systematic review and meta-analysis. The results of the meta-analysis indicated that L-carnitine supplementation was significantly associated with lower levels of CRP in comparison to controls (WMD = -1.23 mg/L; 95% CI: -1.73, -0.72 mg/dL; P < 0.0001). Also, a slight but statistically significant decrease was observed in IL-6 and TNF-α levels (WMD = -0.85 pg/dL; 95% CI: -1.38, -0.32 pg/dL; P = 0.002 and WMD = -0.37 pg/dL; 95% CI: -0.68, -0.06 pg/dL; P = 0.018, respectively).

Conclusion: Our results indicate that L-carnitine reduced inflammatory mediators, especially in studies with a duration of more than 12 weeks. Further studies with different doses and intervention durations and separately in men and women are necessary.