Abstract
BACKGROUND: Several randomized controlled trials (RCTs) have explored the impact of melatonin on body composition and blood pressure (BP). However, the findings from these studies remain a topic of debate. This systematic review and meta-analysis of RCTs sought to evaluate the effects of melatonin consumption on body composition (body weight (BW), body mass index (BMI), waist circumference (WC), hip circumference (HC)) and asleep/daytime BP (systolic blood pressure (SBP) and diastolic blood pressure (DBP)) in adults. METHODS: In order to identify eligible RCTs, a systematic literature search was carried out up to June 2024 in PubMed, Embase, Scopus, and Web of Science without any language restrictions. The I(2) statistic was used to perform heterogeneity tests on the selected studies. After evaluating random effects models based on heterogeneity tests, the weighted mean differences (WMD) with a 95 % confidence interval (CI) were calculated using pooled data. RESULTS: Overall, 28 studies (n = 1,543 participants) met our inclusion criteria. A pooled analysis of studies demonstrated that melatonin consumption led to a significant reduction in HC (WMD: 1.21 cm; 95 % CI: 1.94 to -0.49; P = 0.001), and daytime DBP (WMD: 1.40 mmHg; 95 % CI: 2.46 to -0.34; P = 0.009) in comparison with the control group. However, no substantial effects were observed on BW, BMI, WC, and SBP compared to the control group. Conclusion: The current meta-analysis of RCTs shows that treatment with melatonin reduces HC and daytime DBP levels in adults. However, further well-designed RCTs with large sample sizes and long durations are necessary to determine the effect of this supplement on body composition and BP.