Polyphenol intake and depressive symptoms in young adults: Evidence from a population-based longitudinal study

Background: Due to the high prevalence and incidence of depression among young adults, identifying potential prevention strategies during young adulthood is crucial. Dietary intake is an important determinant of mental health during this stage of the lifespan. Dietary polyphenols, present in plant foods, have been inversely associated with depression in older cohorts; however, the prospective association between polyphenol intake and depression remains unclear, particularly in young adults.Objective: This study aimed to assess the prospective association between the intake of total polyphenols, polyphenol classes, and polyphenol subclasses with depressive symptoms in young adults.Methods: Data from the Raine Study Generation 2 participants at 20-, 22-, and 27-year follow-ups [N = 1,484; 52.7% female; baseline mean age (SD): 20 (0.5)] were used. The exposure variable, polyphenol intake, was estimated from self-reported dietary intakes using Phenol-Explorer. We categorised energy-adjusted polyphenol intake into quartiles. The primary outcome was self-reported depressive symptoms assessed via the 21-item Depression, Anxiety, and Stress Scale (DASS-21) averaged across the three timepoints. Linear mixed-effects models were used to assess the association between the polyphenol intake exposures and depressive symptoms. Sociodemographic characteristics and lifestyle- and health-related behaviours were adjusted for in the multivariable models.Results: Participants in the highest quartiles for flavonol and hydroxybenzoic acid intake had lower depressive symptoms across time than participants in the lowest quartiles [flavonols (Q4 v Q1 model-adjusted mean difference: -1.41, 95%CIs: -2.51, -0.31); hydroxybenzoic acids (Q4 v Q1: -1.42, 95%CIs: -2.54, -0.29)]. We found no evidence of a highest versus lowest association for total polyphenols and all other polyphenol classes and subclasses.Conclusions: Higher dietary intakes of flavonols and hydroxybenzoic acids were associated with lower depressive symptoms. Future studies are required to investigate whether increasing polyphenol intake could protect against depression in young adults.