Effects of zinc supplementation on sleep quality in humans: A systematic review of randomized controlled trials

Background and AimsAlternative therapies, such as zinc supplementation, have been explored as potential interventions for sleep disorders. However, the efficacy of zinc supplementation in improving sleep quality remains uncertain. This systematic review aims to examine the impacts of zinc supplementation on sleep quality in humans.MethodsThe Web of Science, Medline, Scopus, and Google Scholar databases were comprehensively searched to find studies investigating the effect of zinc supplementation on sleep quality. After identifying relevant studies by screening, relevant data were extracted from them. The quality assessment was conducted using the Cochrane quality assessment tool.ResultsThis systematic review included eight studies. The interventions ranged from 4 to 48 weeks, with a daily dose of zinc supplementation varying between 10 and 73.3 mg. The majority of the evidence examined in this review pointed to the significant improvement effect of zinc supplementation on sleep quality in adults compared to the control groups. Furthermore, zinc supplementation did not have a significant effect on sleep disorders. However, there was no consensus about these findings. Also, the effect of supplementation on sleep duration in nonadults was contradictory.ConclusionsThis systematic review suggests that zinc supplementation may lead to improvements in sleep quality. However, more research, primarily clinical trials, is needed to clarify the beneficial effects of zinc supplementation on sleep quality with consideration of dietary zinc intake and the Recommended Dietary Allowances of zinc (RDA) in the different populations. It is also recommended to investigate the effect of zinc supplementation on sleep quality in people with zinc deficiency in future studies.