MAKIKO NAKADE

Background/Objectives: In a demographic increasingly at risk of obesity and hypertension, whether dietary behaviours associated with hypertension prevention, such as restricting salt intake and consuming potassium-rich fruits and vegetables, contribute to obesity prevention is unclear. Therefore, we aimed to investigate the structural associations of dietary salt restriction practices with body mass index (BMI) and the mediating role of the dietary sodium/potassium (Na/K) ratio in middle-aged and older Japanese adults. Methods: This cross-sectional survey included 418 participants aged 40-69 years, residing in Hyogo, Japan. Simultaneous multi-population analysis according to sex was performed using a hypothetical model to explore associations of dietary salt restriction practices with BMI, mediated by the dietary Na/K ratio, as well as the role of BMI-related eating behaviours. Results: Dietary salt restriction was associated with a low dietary Na/K ratio (standardised estimate: -0.21, p = 0.001 for men; -0.19, p = 0.002 for women) in both sexes. Dietary salt restriction was associated with lower values of BMI in men (0.21, p = 0.004), mediated by the Na/K ratio; a direct but relatively weak association with lower values of BMI was observed in women (-0.16, p = 0.018). In men, eating out frequently was associated with higher values of BMI (0.20, p = 0.005). Conclusions: Dietary salt restriction practices in middle-aged and older adults may contribute to obesity prevention, and dietary Na/K ratio may play a mediating role in men but not in women; additionally, eating out was associated with higher values of BMI in men.

Few young Japanese adults regularly consume a well-balanced diet composed of staples, main courses, and sides. We hypothesised that adopting the recommended planetary health diet with regular breakfast consumption would promote well-balanced diets among young Japanese male undergraduates. This study aimed to examine the structural association between the planetary health diet with regular breakfast consumption and a well-balanced diet intake. This cross-sectional study included 142 male engineering undergraduates who completed a 2022 online questionnaire via Google Forms at a public university in Hyogo Prefecture. The planetary health diet comprises the consumption of the recommended eight items. A covariance structure analysis was performed in a hypothetical model with factors (regular breakfast consumption and eight items) potentially associated with the intake of a well-balanced diet at least twice daily. After excluding chicken dishes and nuts from the eight recommended items of the planetary health diet, goodness-of-fit became acceptable. Frequent consumption of the remaining six recommended items (fish, eggs, soybeans/soybean products, dairy foods, vegetables, and fruits) was significantly positively correlated with regular breakfast consumption and a significant positive path to a well-balanced diet. Among male university students, regular breakfast consumption and the planetary health diet may lead to a well-balanced diet.

Abstract This scoping review aimed to identify questionnaire-based dietary assessment methods for use in the National Health and Nutrition Survey (NHNS) in Japan. The search was conducted in three databases (PubMed, Web of Science, and Ichushi) to identify questionnaire such as food frequency questionnaire and dietary history questionnaire validated against dietary recalls or food records for the intakes of both food groups and nutrients among Japanese adults. Study quality was assessed based on previously developed criteria. We extracted the questionnaire characteristics and the design and results of the validation studies. We identified 11 questionnaires, with the number of food items ranging from 40 to 196, from 32 articles of good quality. In the validation studies, participants were aged 30–76 years and 90% of the articles used ≥3 d dietary records as reference. The number of nutrients and food groups with a group-level intake difference within 20% against the reference method ranged from 1 to 30 and 1 to 11, respectively. The range of mean correlation coefficients between questionnaire and reference methods were 0.35–0.57 for nutrients and 0.28–0.52 for food groups. When selecting a survey instrument in the NHNS from the 11 existing questionnaires identified in this study, it is important to select one with high group-level comparison and correlation coefficient values on the intended assessment items after scrutinizing the design and results of the validation study. This review may serve as a reference for future studies that explore dietary assessment tools used for assessing dietary intake in specific representative populations.