Total fat and omega-3 fatty acids intake in relation to serum brain-derived neurotrophic factor (BDNF) levels and psychological disorders in Iranian adults

Considering contradictory findings of previous investigations and growing prevalence of psychological disorders, we investigated association between dietary total fat and omega-3 fatty acids intake with serum brain-derived neurotrophic factor (BDNF) levels, depression, anxiety and psychological distress in Iranian adults. Using a multistage cluster random sampling method, 533 middle-aged adults were included in this cross-sectional study. A validated semi-quantitative 168-item food frequency questionnaire was used to examine dietary intakes. A 12-h fasting blood sample was drawn to measure serum BDNF. Serum BDNF values in the first decile were considered low level. Hospital Anxiety and Depression Scale (HADS) and General Health Questionnaire (GHQ) were used to assess depression, anxiety and psychological distress. A U-shaped relationship between fat intake and prevalence of anxiety and distress was found. The third quartile of fat intake compared to the first quartile was significantly related to 80% decreased odds of depression (OR = 0.20, 95% CI 0.05–0.80), in fully-adjusted model. Participants in the third quartile of fat intake compared to those in the first quartile had significantly 45% lower odds for distress, in the crude model (OR = 0.55, 95% CI 0.33–0.92); however, this association disappeared after considering confounders. There was no significant association between omega-3 fatty acids intake and odds of depression, anxiety or distress. Prevalence of low-BDNF values was higher in participants with depression, as compared to non-depressed subjects (14.9 vs. 9%; P = 0.06). This cross-sectional study illustrated a U-shaped relationship between fat intake and prevalence of anxiety and distress. Moderate intake of fat was related to lower odds of depression. Prevalence of low-BDNF values was slightly higher in subjects with depression compared to non-depressed individuals.