Association of dietary diversity measured by the number of dishes with cardiovascular risk factors among Japanese adults: findings from the National Health and Nutrition Survey, 2018-19

Background The Japanese-style diet has attracted attention as a factor contributing to the Japanese population’s longevity by reducing cardiovascular disease (CVD) mortality. The Japanese-style diet is said to be "ichijusansai" (rice with one soup and three dishes) and is characterized by a high number of dishes. However, the relationship between the number of dishes in all meals (NDAM) and CVD risk factors remains unclear. Methods In this cross-sectional study, we analyzed data from 2,900 participants aged ≥20 years from the 2018-19 National Health and Nutrition Survey. Participants were divided into four groups according to sex and NDAM. NDAM was calculated based on a one-day weighed dietary record, excluding beverages, and including all other dishes and foods. Multivariable relative risks (RRs) were estimated using a modified Poisson regression model adjusted for age, living alone, area, occupation, exercise habits, smoking habits, drinking habits, and total energy intake. Results Participants with higher NDAM were more likely to be older, non-smokers, and physically active. In men, higher NDAM (Groups 2–4) was associated with a lower risk of dyslipidemia compared to Group 1 (the lowest NDAM). In women, an inverse association was observed for overweight/obesity, with Group 4 (the highest NDAM) showing a lower risk than Group 1. Furthermore, a lower risk of hypertension was found in Groups 2–3 compared to Group 1. However, these associations did not remain statistically significant after Bonferroni correction. Conclusion A diet with a high NDAM may be inversely associated with several CVD risk factors among Japanese adults.