Is melatonin as an ergogenic hormone a myth? a systematic review and meta-analysis

Purpose Melatonin supplementation has been disclosed as an ergogenic substance. However, the effectiveness of melatonin supplementation in healthy subjects has not been systematically investigated. The present study analyzed the effects of melatonin supplementation on physical performance and recovery. In addition, it was investigated whether exercise bout or training alter melatonin secretion in athletes and exercise practitioners. Methods This systematic review and meta-analysis were conducted and reported according to the guidelines outlined in the PRISMA statement. Based on the search and inclusion criteria, 21 studies were included in the systematic review, and 19 were included in the meta-analysis. Results Melatonin supplementation did not affect aerobic performance relative to time trial (−0.04; 95% CI: −0.51 to 0.44) and relative to VO 2 (0.00; 95% CI: −0.57 to 0.57). Also, melatonin supplementation did not affect strength performance (0.19; 95% CI: −0.28 to 0.65). Only Glutathione Peroxidase (GPx) secretion increased after melatonin supplementation (1.40; 95% CI: 0.29 to 2.51). Post-exercise melatonin secretion was not changed immediately after an exercise session (0.56; 95% CI: −0.29 to 1.41) and 60 min after exercise (0.56; 95% CI: −0.29 to 1.41). Conclusion The data indicate that melatonin is not an ergogenic hormone. In contrast, melatonin supplementation improves post-exercise recovery, even without altering its secretion.