Nutritional Adequacy Assessment of the Japanese Diet Using the Number of Dishes Compared to Existing Dietary Diversity Indices: A Cross-Sectional Analysis from the 2012 National Health and Nutrition Survey, Japan

The Japanese diet has attracted attention as a factor contributing to the Japanese population's longevity. A typical Japanese meal, traditionally called "ichiju-sansai," is composed of various dishes. This study assessed the nutritional adequacy of the Japanese diet using the number of dishes in all meals (NDAM) compared to existing dietary diversity indices (DDIs). This cross-sectional study used data from the 2012 National Health and Nutrition Survey. A total of 25,976 participants aged =20 y were included in this study. NDAM was calculated for whole dishes or single foods (except supplements and beverages) from one-day weighted dietary records. The food variety score (FVS), number of foods, dietary diversity score (DDS), and number of food groups are some of the existing DDIs. NDAM had relatively high positive correlation coefficients with potassium, magnesium, and dietary fiber. The partial correlation coefficients with an indicator of the overall nutrient adequacy of NDAM was 0.42 for men and 0.42 for women. It was almost the same as that of the FVS (men: 0.44, women: 0.42) and DDS (men: 0.44, women: 0.43). On the other hand, NDAM, similar to existing DDIs, was also positively correlated with nutrient restric-tion in both sexes. These findings indicate that the nutrient adequacy of NDAM is similar to that of the existing DDIs. Because of the higher sodium intake and cholesterol intake in higher NDAM and existing DDIs, the effect of higher NDAM on health outcomes must be investigated in future studies.