DHA mediates the protective effect of fish in new episodes of depression

In a longitudinal cohort study of young Australian adults, the authors reported that for women higher baseline levels of fish consumption were associated with reduced incidence of new depressive episodes during the 5-year follow-up (1). Fish are high in both n-3 fatty acids and tyrosine. In this study, they tried to determine whether n-3 fatty acids or tyrosine explain the observed association. During 2004-2006, a FFQ (nine fish items) was used to estimate weekly fish consumption among 546 women aged 26-36 years. A fasting blood sample was taken and high-throughput NMR spectroscopy was used to measure 233 metabolites, including serum n-3 fatty acids and tyrosine. During 2009-2011, new episodes of depression since baseline were identified using the lifetime version of the Composite International Diagnostic Interview. The n-3 DHA mediated 25·3 % of the association between fish consumption and depression. Tyrosine did not mediate the association. Components in fish other than n-3 fatty acids and tyrosine might be beneficial for women's mental health. The authors conclude that DHA mediates the protective effect of fish consumption on new episodes of depression among women.