Association between Vitamin K Intake and Depressive Symptoms Considering Frailty in Community-Dwelling Older Japanese: A Cross-Sectional Study from the Tarumizu Study

Depression is a significant public health issue affecting relationships, work, and overall quality of life. In Japan, the number of patients with mood disorders, including depression, has increased significantly in recent years. Although malnutrition is known to worsen mental health and elevate the risk of depression and anxiety, the role of specific nutrients in preventing and managing depression remains unclear. This study investigated the association between nutrient intake, particularly vitamin K, and depressive symptoms, accounting for frailty in the Japanese population. Among the 607 participants in this study, 122 (20.1%) experienced depressive symptoms. Vitamin K was independently associated with depressive symptoms using a forward stepwise selection method. The relationship between vitamin K tertiles and depressive symptoms was assessed through multivariate logistic regression analysis. Adjusted for covariates (age, sex, frailty, education level, living status, exercise habits, energy intake, and alcohol consumption), the odds ratios (ORs) for depressive symptoms were significantly lower in tertile 3 compared to tertile 1. The ORs (95% confidence interval, p-value) for tertile 2 and tertile 3 were 0.64 (0.38–1.07, 0.087) and 0.48 (0.28–0.82, 0.008), respectively. Lower vitamin K intake was independently associated with depressive symptoms. Further research is necessary to confirm the role of vitamin K in preventing depressive symptoms.