Effects of melatonin supplementation on blood lipid concentrations: A systematic review and meta-analysis of randomized controlled trials.

BACKGROUND & AIMS: Melatonin supplementation may be associated with blood lipids improvement; however, the current evidence from randomized controlled trials (RCTs) is inconsistent. The present study aimed to systematically review and analyze RCTs assessing the effects of melatonin supplementation on blood lipids.

METHODS: A comprehensive literature search in several database was performed up to January 2017. Quantitative data synthesis was performed using a fixed or random-effects model, with weight mean difference (WMD) and 95% confidence intervals (CI). Standard methods were used for assessment of heterogeneity, meta-regression, sensitivity analysis and publication bias.

RESULTS: A total of 8 RCTs were eligible. Meta-analysis suggested a significant association between melatonin supplementation and a reduction in triglycerides (WMD: -31.54 mg/dL, 95% CI: -50.71, -12.38, p = 0.001), and total cholesterol levels (WMD: -18.48 mg/dL, 95% CI: -35.33, -1.63, p = 0.032), while no significant effect on LDL-C (WMD: -2.37 mg/dL, 95% CI: -11.61, -6.86, p = 0.615) and HDL-C (WMD: 1.28 mg/dL, 95% CI: -0.66, 3.23, p = 0.197) was found. In sub-group analysis, a significant decrease in triglycerides was found at doses ≥8 mg/d and when trials last ≥8 weeks. In addition, a significant decrease of total cholesterol was found at doses ≥8 mg/d and when total cholesterol baseline levels were ≥200 mg/dL.

CONCLUSIONS: Melatonin supplementation has significant effects on triglycerides and total cholesterol levels, which was more evident in higher dose and longer duration and also in a higher concentration of cholesterol levels. Further studies are required to determine the benefits of melatonin on lipid profile.