The Impact of Probiotic Supplementation on the Sleep Quality of Humans: A Review of Results of Randomized, Blinded, Controlled Studies

Sleep is the key factor influencing physical and psychological health. Several factors influence sleep, including lifespan, circadian entrainment, diet, stress, and occupation. Pharmacological (for example, histamine type 1 receptor blockers) and non-pharmacological (for example, cognitive-behavioral therapy) therapeutic approaches are used to alleviate sleep disorders. The gut microbiota has an important role in the pathogenesis of sleep-related disorders. Studies suggested that restoring the healthy gut microbiota could improve sleep quality. Hence, related randomized, blinded, controlled studies were reviewed to know the impact of probiotic supplementation on sleep quality. Altered Firmicutes/Bacteroidetes ratio and reduced α-diversity were associated with insomnia, sleep deprivation and rapid eye movement sleep behavior disorder. The literature survey revealed that probiotic supplementation improved healthy subjects' sleep quality and mood states. Probiotic supplementation could improve sleep quality by improving gut microbiota, intestinal integrity, blood- -brain barrier function, brain functions and neurotransmitter regulation. The underlying mechanisms through which probiotic supplementation exerts its beneficial effects on sleep disorders remain unclear. Further research involving a variety of probiotic strains, along with long-term follow-up studies, is needed to validate the potential of probiotics as a complementary therapeutic approach for managing sleep disorders and enhancing sleep quality.