Prospective study on the association between dietary non-enzymatic antioxidant capacity and depressive symptoms

Summary Background & aims Oxidative stress has been suggested to play an important role in the pathophysiology of depression, and a diet high in antioxidants may improve mood. However, studies addressing this issue are scarce. The aim of this cohort study was to investigate the prospective association between dietary non-enzymatic antioxidant capacity (NEAC) in overall diet and depressive symptoms in Japanese employees. Additionally, we examined the association separated by dietary NEAC sources. Method Participants were 911 workers without depressive symptoms at baseline and participated in 3-y follow-up survey. Dietary NEAC was determined from a database of NEAC measurements obtained by ferric reducing antioxidant power (FRAP) and oxygen radical absorbance capacity (ORAC). Dietary NEAC was calculated by multiplying the estimated NEAC values with the consumed amount and summing up those values. Depressive symptoms were assessed using the Center for Epidemiologic Studies Depression Scale. Logistic regression was used to estimate odds ratios of depressive symptoms according to overall NEAC and separately from foods and beverages. Results At 3-y follow-up, 153 (16.8%) workers were newly identified as having depressive symptom. No significant associations were found between higher level of overall dietary NEAC and decreased risk of depressive symptoms after adjustment for potential confounders (overall: FRAP, P for trend = 0.19 and ORAC, P for trend = 0.20). Likewise, neither higher dietary NEAC from foods nor beverages were related with lower depressive symptoms. Conclusion Our findings did not support an inverse association between dietary NEAC and the risk of depressive symptoms in Japanese workers.