The association of sleep quality and insomnia with dietary intake of tryptophan and niacin

Abstract

Introduction: Dietary intake of tryptophan and niacin have been related to sleep. However, the sleep-promoting effects of these nutrients are still under investigation. The aim of the current study was to examine the relationship between daily dietary intake of tryptophan and niacin and sleep. Materials and methods: A survey on past week's dietary intake (food frequency questionnaire)was completed by N = 509 Dutch university students (20.8 years old). The SLEEP-50 questionnaire subscale on insomnia was completed, and sleep quality (0-10 score) and total sleep time (TST) were also assessed. Daily intake of tryptophan and niacin was correlated to insomnia rating, sleep quality and TST using nonparametric (Spearman) correlations. Analyses were conducted for the group as a whole, and for men (N = 143) andwomen (N = 366) separately. Results: Mean [SD] scores of insomnia (14.6 [4.3]), sleep quality (7.3 [1.2]), TST (7.7 h [0.9]), and daily dietary intake of tryptophan (0.618 g [0.3]) and niacin (15.88 mg[6.7])were within normal ranges. Insomnia scores correlated significantlywith dietary intake of tryptophan (r = -0.180, p = 0.0001) and niacin (r = -0.157, p = 0.001). When controlling for total caloric intake, the partial correlation between tryptophan intake and insomnia remained significant (r = -0.105, p = 0.029). Niacin intake also correlated significantly with sleep quality (r = .094, p = 0.045). No significant correlation was found with TST. In men, insomnia scores correlated significantly with dietary intake of tryptophan (r = -0.287, p = 0.002) or niacin (r = -0.243, p = 0.008). Sleep quality scores also correlated significantly with dietary intake of tryptophan (r = 0.205, p = 0.026) and niacin (r = -0.240, p = 0.008). In women, none of the correlations were significant. Conclusion: A modest but significant association was found between dietary intake of tryptophan and niacin and insomnia and sleep quality. The nature and causes of the observed gender differences require further investigation.