Comprehensive effects of various nutrients on sleep.

Sleep problems have become common among people today. Sleep disorders are closely associated with physiological and psychological diseases. Among the ways of improving objective or subjective sleep quality, controlling elements associated with food intake can be more efficient than other methods in terms of time and cost. Therefore, the purpose of this study was to understand the effects of nutrients and natural products on sleep. An extensive literature search was conducted, and related articles were identified through online databases, such as Elsevier, Google Scholar, PubMed, Springer, and Web of Science. Expert opinion, conference abstracts, unpublished studies, and studies published in languages other than English were excluded from this review. The effects of macronutrients and diet adjustment on sleep differed. Although not all nutrients independently affect sleep, they comprehensively affect it through tryptophan metabolism. Furthermore, natural foods related to GABA have an effect on sleep similar to that of sleeping pills. Taken together, our results suggest that humans can control both their objective and subjective sleep quality based on their lifestyle and food consumption. However, until now, direct studies on the relationship between human sleep and nutrition, such as clinical trials, have been insufficient. As both objective and subjective sleep quality are the factors determining the quality of life of individuals, further studies on those are needed to improve it.