Dairy intake and sleep duration and quality: a systematic review and dose–response meta-analysis of observational and interventional studies

Due to the complexities of modern life, sleep disorders have become prevalent, leading to a number of physical and mental health issues. This meta-analysis was conducted to explore the association between dairy consumption and sleep parameters. Following a database search, 29 citations (25 observational and 4 trials) were included in the meta-analysis. In observational studies, a dose–response association was observed between dairy ingestion and better sleep quality and duration. Consumption of milk had a linear association with good sleep quality at doses up to 2 servings/day. The estimated reduction in risk of poor sleep quality was 15% for each serving increase in milk consumption (OR = 0.85; 95% CIs: 0.76, 0.94, P = 0.001). Consumption of dairy also showed an association with good sleep quality at doses up to 1.5 servings/day. However, higher doses of milk (> 3 servings/day) and dairy (> 2 servings/day) showed a trend towards an increased risk of poor sleep quality. For short sleep duration, consumption of milk in doses > 0.7 servings/day showed a positive association with sleep duration. The highest vs. lowest analysis also showed an association between yogurt, but not cheese, consumption and sleep duration. In trials, dairy consumption indicated a significant improvement in sleep quality (mean difference = -0.49; 95% CIs: -0.92, -0.05, P = 0.031), a finding which was confirmed by dose–response analysis. Overall, results showed a dose–response association between dairy and especially milk and better sleep quality and duration.