Dietary zinc intake and the risk of depression in middle-aged men: A 20-year prospective follow-up study

BackgroundZinc is an immunomodulatory trace element suggested to be beneficial in the augmentation of antidepressant therapy. Cross-sectional studies have also suggested an association between low dietary zinc and depression. This study examined the association between dietary zinc intake and depression in a prospective setting in initially depression-free men during a 20-year follow-up.MethodsThe study formed a part of the population-based Kuopio Ischemic Heart Disease Risk Factor (KIHD) Study, and comprised 2317 Finnish men aged 42-61 years. Zinc intake was assessed at baseline by a 4-d food record. Baseline depression severity was recorded with the Human Population Laboratory Depression Scale. In the prospective setting, depression was defined as having received a hospital discharge diagnosis of unipolar depressive disorder. Individuals who at baseline had elevated depressive symptoms were excluded (n=283).ResultsAltogether, 60 (2.7%) individuals received a hospital discharge diagnosis of depression during the 20-year follow-up. In Cox regression analysis adjusted for age, baseline depression severity, smoking, alcohol use, physical exercise and the use of dietary supplements, belonging to the lowest tertile of energy-adjusted zinc intake was not associated with an increased depression risk (RR 1.06, 95% CI 0.59-1.90).LimitationsThese observations may not be generalizable to women, or to individuals with a depression level not warranting hospitalization.ConclusionsOur findings suggest that a low dietary zinc intake may not longitudinally precede depression in men. Dietary zinc intake may not have relevance for the prevention of depression in middle-aged men with a sufficient dietary zinc intake.