Dietary melatonin, chronotype, and night eating syndrome in relation to sleep quality among adults.

OBJECTIVE: Dietary melatonin has attracted increasing interest because of its potential relevance to circadian regulation and sleep health. However, evidence regarding its relationship with chronotype, night eating behaviors, and sleep quality remains limited. This study aimed to examine the associations among estimated dietary melatonin intake, chronotype, night eating behaviors, and sleep quality in adults and to explore the cross-sectional indirect association among chronotype, night eating behaviors, and sleep quality. METHODS: This cross-sectional study was conducted in Istanbul, Türkiye, between November 2024 and June 2025 and included 325 adults aged 18-65 years. Sleep quality was assessed using the Pittsburgh Sleep Quality Index (PSQI), chronotype using the Morningness-Eveningness Questionnaire (MEQ), and night eating behaviors using the Night Eating Questionnaire (NEQ). Dietary melatonin intake was estimated using a modified food frequency questionnaire based on melatonin-containing foods. Pearson correlation analysis, multiple linear regression, binary logistic regression, and an exploratory cross-sectional indirect-association analysis using PROCESS Model 4 were performed. RESULTS: Mean total dietary melatonin intake was 10.485 ± 13.306 μg/day. PSQI scores were positively correlated with NEQ scores (r = 0.537, p < 0.001) and negatively correlated with MEQ scores (r = -0.159, p = 0.004). In the multiple linear regression model, NEQ score was positively associated with PSQI score (B = 0.198, standardized β = 0.491, 95% CI: 0.156-0.239, p < 0.001), whereas MEQ score was negatively associated with PSQI score (B = -0.067, standardized β = -0.189, 95% CI: -0.102 to -0.032, p < 0.001). Female sex and chronic disease presence were also statistically significant, whereas total and evening dietary melatonin intake were not associated with PSQI score after adjustment for the measured covariates. In the logistic regression model for night eating syndrome risk, PSQI score (OR = 1.328, 95% CI: 1.185-1.488, p < 0.001) and MEQ score (OR = 0.941, 95% CI: 0.897-0.988, p < 0.001) were statistically significant. The exploratory indirect-association analysis identified a statistically significant indirect association among chronotype, night eating behaviors, and sleep quality. CONCLUSION: Eveningness tendency and higher night eating scores were associated with poorer sleep quality, whereas estimated dietary melatonin intake was not associated with sleep quality after adjustment for the measured covariates. These findings should be interpreted as cross-sectional and hypothesis-generating. Longitudinal and intervention studies are needed to clarify temporal relationships and to determine whether chronotype-informed or chrononutrition-based approaches influence sleep-related outcomes.