Depression has been linked to the overall diet using both exploratory and pre-defined methods. However, neither of these methods incorporates specific knowledge on nutrient-disease associations. The aim of the present study was to empirically identify dietary patterns using reduced rank regression and to examine their relations to depressive symptoms. Participants were 2006 Japanese employees aged 19-69 years. Depressive symptoms were assessed using the Center for Epidemiologic Studies Depression Scale. Diet was assessed using a validated, self-administered diet history questionnaire. Dietary patterns were extracted by reduced rank regression with 6 depression-related nutrients as response variables. Logistic regression was used to estimate odds ratios of depressive symptoms adjusted for potential confounders. A dietary pattern characterized by a high intake of vegetables, mushrooms, seaweeds, soybean products, green tea, potatoes, fruits, and small fish with bones and a low intake of rice was associated with fewer depressive symptoms. The multivariable-adjusted odds ratios of having depressive symptoms were 0.62 (95% confidence interval, 0.48-0.81) in the highest versus lowest tertiles of dietary score. Results suggest that adherence to a diet rich in vegetables, fruits, and typical Japanese foods, including mushrooms, seaweeds, soybean products, and green tea, is associated with a lower probability of having depressive symptoms.

This study aimed to examine the cross-sectional association of demographic and lifestyle factors with serum brain-derived neurotrophic factor (BDNF) concentrations in a Japanese working population. Participants were 1678 men and 172 women aged 19-69 years who received health check-ups and participated in a nutrition and health survey. Depressive symptoms were assessed using the Center for Epidemiologic Studies Depression (CES-D) scale. Dietary intake was assessed using a validated self-administered diet history questionnaire. Serum BDNF concentrations were measured using a solid phase sandwich enzyme-linked immunosorbent assay. Multiple linear regression analysis was used to estimate the mean and 95% confidence interval of serum BDNF concentrations according to demographic and lifestyle factors. Higher body mass index (BMI) was significantly associated with higher circulating BDNF concentrations. Current smokers had significantly higher mean BDNF concentrations than never-smokers. BDNF concentrations were not associated with folate and 25-hydroxyvitamin D concentrations in serum, or dietary eicosapentaenoic acid and docosahexaenoic acid intake. Serum BDNF concentrations were not associated with depressive symptoms or CES-D score per se. In this study, higher BMI and smoking were associated with higher concentrations of serum BDNF, while nutrients that have been linked to depression were not associated with BDNF concentrations among Japanese workers.

This study was aimed to examine the cross-sectional association of protein, carbohydrate, and fat intake with depressive symptoms among 1794 Japanese male workers aged 18-69 years who participated in a health survey. Dietary intake was assessed with a validated self-administered diet history questionnaire. Depressive symptoms were assessed using the Center for Epidemiologic Studies Depression (CES-D) scale. Odds ratio of depressive symptoms (CES-D scale of ≥16) was estimated by using multiple logistic regression with adjustment for covariates including folate, vitamin B6, vitamin B12, polyunsaturated fatty acid, magnesium, and iron intake. Multivariable-adjusted odds ratio of depressive symptoms for the highest quartile of protein intake was 26%, albeit not statistically significant, lower compared with the lowest. The inverse association was more evident when a cutoff value of CES-D score ≥19 was used. The multivariable-adjusted odds ratios (95% confidence intervals) for the highest through lowest quartile of protein intake were 1.00 (reference), 0.69 (0.47-1.01), 0.69 (0.44-1.09), and 0.58 (0.31-1.06) (P for trend=0.096). Neither carbohydrate nor fat intake was associated with depressive symptoms. Our findings suggest that low protein intake may be associated with higher prevalence of depressive symptoms in Japanese male workers.