The Impact of Milk-Derived Bioactives and Fortified or Fermented Milk Products on Sleep Quality: A Systematic Review and Meta-Analysis.

CONTEXT: Milk-derived bioactives and fortified or fermented milk products may have sleep-promoting effects, but evidence remains inconsistent. OBJECTIVE: The effects of milk-derived bioactives and fortified or fermented milk products on sleep-related outcomes in randomized controlled trials (RCTs) were evaluated in this systematic review and meta-analysis, and associations between milk/dairy consumption and sleep quality in cross-sectional studies are summarized. Subgroup analyses were conducted according to health status, intervention type, and study duration. DATA SOURCE: Relevant studies were identified from the PubMed, Embase, CINAHL, Cochrane Library, and Web of Science databases. DATA EXTRACTION: Twenty-five studies were included in the systematic reviews, of which 11 RCTs were eligible for meta-analysis. DATA ANALYSIS: Milk-derived bioactive and fortified or fermented milk-product interventions significantly improved sleep efficiency (SEff), the percentage of time in bed spent asleep (standardized mean difference for SEff [SMDSEff] = 0.45; 95% CI, 0.21-0.70). Post hoc subgroup analyses further demonstrated that milk supplementation induces greater improvements in SEff (SMDSEff = 0.52; 95% CI, 0.27-0.76); wake after sleep onset (WASO), the minutes awake after initial sleep onset (mean difference for WASO [MDWASO] = -8.24; 95% CI, -13.64 to -2.84) among individuals with sleep or health disturbances; and reduced sleep latency (SL) (ie, time from lights off to sleep onset) in generally healthy participants (MDSL = -2.17; 95% CI, -4.09 to -0.25). Among intervention types, only milk protein and peptides significantly improved SEff (SMDSEff = 0.51; 95% CI, 0.23-0.79). Interventions lasting longer than 4 weeks enhanced SEff (SMDSEff = 0.60; 95% CI, 0.36-0.83) and WASO (MDWASO = -10.26; 5% CI, -15.42 to -5.09). CONCLUSION: Evidence from RCTs suggests that milk-derived bioactives and fortified or fermented milk products may improve sleep, particularly in individuals with impaired sleep or underlying health conditions. Cross-sectional studies suggest generally positive but heterogeneous associations between milk/dairy consumption and sleep quality. These findings highlight the importance of considering supplementation type and duration when designing or interpreting studies on diet-sleep relationships. SYSTEMATIC REVIEW REGISTRATION: PROSPERO registration No. CRD420251023926.