Association between niacin intake and depression: A nationwide cross-sectional study

The association between dietary intake and depression is receiving increasing attention. However, the relationship between depressive symptoms and niacin intake is still unclear. The purpose of this study was to explore the association between niacin intake and depressive symptoms. We used univariate analysis and multivariate logistic regression equations to explore the association between covariates or niacin intake and depression. Generalized additive models and smoothing fitted curves were used to examine the presence of nonlinear relationships. Upon finding a nonlinear relationship, a recursive algorithm was used to calculate the inflection point . Population differences were also explored through stratified analysis. In the model adjusted for all covariates，the ORs (95 % CI) for the association between niacin intake and depression were 0.94 (0.87, 1.01), which was no statistical significance. However, the result of the linear trend test with quartiles of niacin intake indicated the association between niacin intake and depression may be U-shaped. The generalized additive model confirmed this U-shaped relationship, finding an inflection point (26.6 mg/d). An opposite relationship was observed before and after the inflection point, with ORs (95 % CI) of 0.77 (0.68, 0.87) before the inflection point and 1.13 (1.01, 1.28) after the inflection point. The association in men, Mexican American, White, adults aged<40, and BMI <30 was consistent with the overall tendency. We found a U-shaped association between niacin intake and depression in the general American population, and the same association was observed in men, Mexican American, White, adults aged < 40, and BMI < 30.