OBJECTIVES: To our knowledge, the overall nutritional quality of the Japanese diet has not been assessed previously. The aim of this study was to investigate the relationship between adhering to a Japanese diet and nutrient intake. METHODS: We conducted a cross-sectional study of 1129 Japanese persons ≥70 y of age. Dietary habits were assessed using a food frequency questionnaire. The primary outcome was nutrient intake (12 components of NRF9.3 index). The overall nutrient adequacy (ONA) score was applied for assessing the potential of nutrient density. Correlation analysis was performed to compare the Japanese Diet Index (JDI) and nutrient intake, and multiple regression analysis was used to simulate the modified JDI (MJDI). RESULTS: The JDI was positively correlated with all nine beneficial nutrients, and negatively correlated with two nutrients (saturated fat and sugar). The JDI was significantly correlated with the ONA score (Spearman's coefficient = 0.248). The MJDI, which was defined by the coefficients for seven food items, was significantly correlated with the ONA score (Spearman's coefficient = 0.515). However, the JDI and MJDI were correlated with higher sodium intake. CONCLUSIONS: The present findings suggest that adhering to a Japanese diet defined by the JDI score is associated with better nutrient intake. However, this dietary pattern also appears to be associated with high sodium intake.