Estimated Dose-Dependent Associations Between Dietary Intake and Stress Responses in Adolescents and Young Adults: Evidence from a Regional Observational Study in Japan.
Hazama M, Kagami-Katsuyama H, et al. • Nutrients • 2026
Cross-sectional analysis of Japanese adolescents and young adults found that in females, the presence or absence of dark-green and yellow vegetable intake was associated with stress response magnitude, while bread, noodles, and starchy food intake showed a monotonic positive association with fatigue.
Key Findings
Results
In females, the presence or absence of dark-green and yellow vegetable intake—rather than frequency of intake—was associated with the magnitude of stress responses.
The association was nonlinear, meaning whether vegetables were consumed at all mattered more than how often they were consumed
This pattern was observed specifically in female participants (n = 124, age = 29.8 ± 5.77)
The finding suggests a threshold effect rather than a dose-dependent gradient for this food group
Mental and physical stress reactions were measured using the Brief Job Stress Questionnaire (BJSQ)
Results
Intake frequency of bread, noodles, and starchy foods showed a monotonic positive association with fatigue in females.
The association was linear (monotonic positive), meaning higher intake frequency corresponded to greater fatigue
This contrasts with the threshold-type association seen for dark-green and yellow vegetables
The finding applied to the female subsample studied in the cross-sectional regional observational study
Fatigue was assessed as a physical stress-reaction item within the Brief Job Stress Questionnaire
Methods
Structural equation modeling (SEM) was demonstrated to allow ordinal food frequency questionnaire categories to be treated as integer values representing monthly intake frequency.
The food frequency questionnaire (FFQ) provides ordinal frequency categories rather than continuous data
The authors show SEM enables these ordinal data to be used to estimate dose-response associations with stress outcomes
This methodological approach allowed estimation of both linear and nonlinear associations between food-group-specific intake frequencies and stress responses
The sample consisted of males (n = 48, age = 32.3 ± 5.23) and females (n = 124, age = 29.8 ± 5.77) from a regional observational study in Japan
Background
The study examined the bidirectional relationship between diet and mental wellbeing in an adolescent and young adult (AYA) population in Japan.
The study used cross-sectional data, meaning causal direction between diet and stress could not be determined
The authors acknowledge the bidirectional nature: nutritional psychiatry examines diet effects on mental health, while emotional-eating research focuses on the reverse
The total sample was 172 participants (males: n = 48; females: n = 124)
The authors note the associations 'do not disentangle the bidirectional causal relationship between diet and mental-physical health'
Conclusions
The study found both linear and nonlinear dose-response associations depending on the specific food group examined.
Dark-green and yellow vegetables showed a nonlinear (threshold) association with stress responses in females
Bread, noodles, and starchy foods showed a linear (monotonic positive) association with fatigue in females
The analysis covered multiple food groups assessed by the FFQ
The authors conclude the study provides 'evidence on the linear and nonlinear associations between food-group-specific intake frequencies and stress responses in the AYA population'
What This Means
This research examined whether eating certain foods more or less often is linked to stress and fatigue in young Japanese adults. Researchers surveyed 172 people (mostly women in their late 20s to early 30s) about how often they ate various food groups and measured their mental and physical stress reactions using a standardized questionnaire. They used a statistical technique called structural equation modeling to analyze how changes in eating frequency related to changes in stress levels.
The study found two distinct patterns in women. For dark-green and yellow vegetables, simply eating them at all—rather than how frequently—appeared to matter for stress responses, suggesting a possible 'threshold' effect. For starchy foods like bread and noodles, eating them more often was directly linked to higher fatigue in a step-by-step fashion, meaning the more frequently they were consumed, the greater the reported fatigue. These patterns were not examined or reported for male participants.
Because this was a cross-sectional study (a one-time snapshot rather than a follow-up over time), it cannot determine whether diet influences stress levels, stress influences eating habits, or both. This research suggests that different food groups may relate to stress in different ways—some showing gradual dose-related links and others showing 'all-or-nothing' patterns—and that future studies should account for these distinctions when exploring how diet and mental wellbeing interact in young people.
Hazama M, Kagami-Katsuyama H, Ito N, Maeda-Yamamoto M, Kimoto H, Nishihira J. (2026). Estimated Dose-Dependent Associations Between Dietary Intake and Stress Responses in Adolescents and Young Adults: Evidence from a Regional Observational Study in Japan.. Nutrients. https://doi.org/10.3390/nu18162612