This meta-analysis was conducted on 15 randomized clinical trials investigating melatonin supplementation’s effects, compared to placebo, on fasting blood glucose, insulin resistance, and glycated hemoglobin in over 800 subjects either healthy (n = 1 trial) or with type 2 diabetes (n = 3 trials), liver steatosis (n = 2), metabolic syndrome (n = 3), cardiovascular disease (n = 1), schizophrenia, under psychotics, with Parkinson disease (n = 4), polycystic ovary syndrome (n = 1) or under hemodialysis (n = 1). Melatonin doses ranged from 3 to 10 mg daily. Results indicate that 56% of the trial showed benefits from supplementation with melatonin in diabetes parameters compared with placebo. The meta-analysis showed significant results for fasting blood glucose [mean difference: -4.65; 95% CI: -8.06, -1.23; p = < 0.01; I2 = 58%], glycated hemoglobin [mean difference: -0.38; 95% CI: -0.67, -0.10; p = 0.30; I2 = 18%], and insulin resistance [mean difference: -0.58; 95% CI: -1.00, -0.15; p = 0.17; I2 = 35%]. In conclusion, melatonin supplementation was useful for reducing diabetes markers when compared to placebo.
Delpino FM, Figueiredo LM, Nunes BP. Effects of melatonin supplementation on diabetes: A systematic review and meta-analysis of randomized clinical trials. Clin Nutr. 2021 Jul;40(7):4595-4605.