Background/Objectives: With increasing life expectancy, interest in healthy aging has grown substantially. Dietary habits are among the key factors that contribute to achieving healthy aging. This study analyzes the relationship between dietary habits and the age–health association in older adults, using the first two years of data from an ongoing annual cohort study conducted in a region of Japan. Methods: We used observational data from approximately 1200 community-dwelling males and females aged 55 to 75 at baseline, drawing on the first two years of a ten-year annual cohort study conducted from 2023 to 2032. First, dietary habits were classified using an ordinal latent block model (OLBM), a model-based clustering approach applied to food frequency questionnaire (FFQ) data. We then examined whether the age–health gradient—measured across 33 indicators—differed significantly across the derived dietary habit types, using random effects models. Results: Dietary habits in the analyzed sample were categorized into six distinct types. Parameter estimates from the model suggest that the extracted patterns represent a continuum ranging from low to high dietary diversity. Regression analyses indicated that, in females, a negative association between age and LDL-C levels was observed among those with highly diverse dietary habits. Conclusions: The data-driven classification of dietary habits based on FFQ responses highlights the potential importance of dietary diversity.

Background/Objectives: The improvement of sleep quality is unquestionably a critical issue in public health. While numerous factors influence sleep quality, the relative importance of dietary habits remains insufficiently understood. The objective of this study is to evaluate the contribution of dietary habits by quantitatively comparing the effects of various determinants of sleep quality. Methods: Using sleep diary data from healthy males and females residing in a specific region of Japan, we estimated a dynamic multivariate panel model (DMPM) to obtain posterior predictive distributions on a scale that allows for comparisons across factor categories. Three outcome variables were adopted to measure sleep quality: presence or absence of daytime drowsiness, ease of falling asleep, and ease of waking up. The determinants of sleep quality examined in the analysis were categorized into six groups: stress factors, bedtime conditions, weather conditions, physical characteristics, exercise habits, and dietary habits. Results: The analysis revealed that although there were some seasonal and gender differences, dietary habits showed effect sizes that were no smaller than those of other determinants across all outcome variables. Conclusions: These results suggest that improving dietary habits, along with enhancing exercise habits and bedtime conditions, is a valid and equally important strategy for promoting better sleep.

Background. Japanese dietary patterns have traditionally focused on vegetables, legumes, and fish; however, in the last few quarters of the century, the consumption of meat, processed food, and ultra-processed food has become popular. It is anticipated that these changes in the Japanese dietary environment will increase the risk of developing psychosomatic disorders. Methods. In this study, we examined the relationship between dietary habits, psychosomatic disorders, and a sense of achievement. For men and women aged 20–80 years (n = 851) living in and around Ebetsu City, Hokkaido, Japan, a questionnaire on dietary habits over the past year, including mental and physical stress and a sense of achievement, was administered. The associations between dietary habits and psychosomatic disorders or a sense of achievement were analyzed using logistic regression (n = 654). Results. The associations between dietary habits and psychosomatic disorders differ depending on sex and age. We found that subjects who consumed more processed meat and ultra-processed food reported more psychosomatic disorders. On the other hand, those who perceived a sense of achievement consumed higher amounts of vegetables, albeit with a lower fish intake. Conclusions. In this study, we demonstrated that dietary habits and food ingredients are associated with mental and physical stress and a sense of achievement. Fish, which is considered to be good for the body, was mostly consumed by subjects who experienced mental and physical stress. These data indicate that highly stressful conditions may encourage fish consumption, as the body needs to mitigate psychosomatic disorders.

Background/Objectives: Improving one’s diet for the purpose of promoting health is constrained by people’s ingrained eating habits, as the eating patterns that align with their established habits do not necessarily correspond to a healthy way of eating. In addressing the issue of improving diet while taking both health and habits into consideration, this paper focuses on three concepts of complementarity related to food combinations and presents an approach using Japanese data. Methods: This paper first organizes three concepts of complementarity related to food combinations. The three concepts of complementarity are formulated based on (i) nutrients, (ii) habits, and (iii) recipes. The definitions of measurement scales corresponding to these concepts are also discussed. Results: Using data from a specific region in Japan, we analyzed three types of complementarities related to food combinations across different gender and age groups. This approach enabled us to visualize the potential for dietary improvements and identify effective strategies tailored to each group. For instance, among females aged 50 and above in this region, it was found that recipes incorporating combinations such as (α) milk and pasta, (β) salmon and pasta, (γ) horse mackerel or sardines with carrots, and (δ) onions with taro can efficiently support dietary improvement for this demographic, building upon their established dietary habits. The differences in recommended recipes for each group are due to variations in nutrients that tend to be insufficient and differences in established eating habits. Conclusions: A combination of foods with high (i) complementarity of nutrients constitutes a healthy diet, whereas a combination of foods with low (ii) complementarity in habits reflects dietary behaviors that are not sufficiently practiced within the relevant sub-population at present. Meanwhile, combinations of foods with high (iii) complementarity in recipes can serve as tools to bridge the gap between healthy eating patterns and established dietary habits.

Background/Objectives: The relationship between diet and mental wellbeing is bidirectional: nutritional psychiatry examines effects of diet on mental health, whereas emotional-eating research focuses on the reverse. Although dose–response links between nutrient intake and health outcomes are well studied, few have analyzed such relationships between food-group intake and stress. Using cross-sectional data from a regional observational study of Japanese adolescents and young adults (males: n = 48, age = 32.3 ± 5.23; females: n = 124, age = 29.8 ± 5.77), we estimated dose–response associations between intake frequency of various food groups and stress responses. Methods: Mental and physical health was assessed using the response values for the mental and physical stress-reaction items in the Brief Job Stress Questionnaire. Intake frequency for each food group was obtained from a food frequency questionnaire (FFQ). Although the FFQ provides ordinal frequency categories, we demonstrate that structural equation modeling allows these data to be treated as integer values representing monthly intake frequency, enabling the estimation of associations with stress responses. Results: The analysis showed that, in females, the presence or absence of intake—rather than the frequency of intake—of dark-green and yellow vegetables was associated with the magnitude of stress responses. In contrast, for bread, noodles, and starchy foods, a monotonic positive association was observed between intake frequency and fatigue. Conclusions: Although these associations do not disentangle the bidirectional causal relationship between diet and mental–physical health, they provide evidence on the linear and nonlinear associations between food-group–specific intake frequencies and stress responses in the AYA population.