Dietary Carotenoid Intake and Sleep: A Narrative Review of Evidence from Human and In Vivo Animal Studies.

Background/Objectives: Carotenoids are dietary bioactive compounds found primarily in red, yellow, and orange fruits and vegetables that possess antioxidant and anti-inflammatory properties. These properties are increasingly known to be relevant for sleep health. Hence, this narrative review aims to summarize current evidence on the relation between carotenoids and sleep. Methods: PubMed and Scopus were searched for observational and intervention studies in adults and in vivo preclinical studies examining carotenoid exposure in relation to sleep-related outcomes. Eligible studies were screened using predefined criteria, and findings were synthesized narratively. Results: Of the 1042 studies screened, 29 met the inclusion criteria, including 14 observational, 11 intervention, and 4 preclinical studies. Across observational studies, higher dietary intake or serum carotenoid concentrations were generally associated with more favorable sleep outcomes, including sleep quality, duration, and sleep-related symptoms, although heterogeneous sleep-outcome definitions limited cross-study comparison. Nine intervention studies (81.8%) reported improvement in at least one sleep-related outcome following carotenoid supplementation. However, improvement was not consistently significant compared with placebo. Preclinical studies provided preliminary evidence that selected carotenoids improved sleep-wake parameters, including dose-dependent increases in total sleep and non-REM sleep duration, as well as reductions in wakefulness. Conclusions: Emerging evidence suggests that carotenoids may contribute to sleep health. However, current evidence remains limited and heterogeneous. Additional research is needed to determine the effects of specific carotenoids, optimal doses, and underlying biological mechanisms to better inform evidence-based clinical practice recommendations.