Eating more legumes and vegetables lowers stress by increasing beneficial gut bacteria, study finds

Eating more legumes and vegetables lowers stress by increasing beneficial gut bacteria, study finds

Japanese researchers show that diets rich in legumes and vegetables can help lower stress levels - not just through nutrients, but the growth of specific gut bacteria.

In a study recently published in the journalClinical nutrition aspensThe researchers examined the relationship between diet quality, stress and gut microbiota. People are exposed to stressors on a daily basis, and prolonged exposure can have a negative impact on the body and mind. In addition, this can lead to migraines, neurosis, stomach ulcers, anxiety and depression. The gut microbiota has been linked to stress, with studies indicating that stress can alter the composition of the gut microbiota and that the gut microbiota can in turn influence stress responses.

Additionally, epidemiological studies suggest that diet plays a critical role in stress, with different foods and nutrients influencing stress levels. Nutrient profiling is the science of ranking or classifying foods based on their nutritional value in promoting health and preventing disease. Nutrient Profile Models (NPMs) serve as comprehensive assessment indices that consider multiple nutrients simultaneously rather than focusing on a single one.

Various NPMs have been developed to assess diet quality. One such NPM is the Nutrient Rich Food Index 9.3 (NRF9.3), which can be applied to individual foods, menus, meals and entire diets. However, there are limited studies on the relationship between health indicators and NRF9.3. Furthermore, prior to this research, no study has examined the relationship between NRF2.3 and gut microbiota or stress.

About the study

Foods acted as entry points: natto, tomatoes and green peppers were positioned as starting nodes in the network model, initiating the diet → microbiome → stress chain.

In the present study, researchers examined the relationships between diet quality, stress and gut microbiota. They used data from the Sukoyaka Health Survey among Japanese adults aged 20 to 80, conducted twice a year (in winter and summer). This study analyzed data from the summers of 2019 and 2020. The short questionnaire (BJSQ) assessed mental and physical stress response ratings, and the food frequency questionnaire (FFQ) assessed food and nutrient intake.

Gut microbiota composition was analyzed using shotgun metagenomics. NRF9.3 was used to determine diet quality. NRF9.3 scores were calculated using FFQ data, with higher values ​​indicating a diet rich in beneficial nutrients (e.g. minerals, fiber, fiber, vitamins) and low in nutrients to be consumed moderately (e.g. saturated fat, sodium, added sugars).

Hierarchical clustering was used to stratify subjects based on their stress levels. Gut microbiota composition and diet quality were compared between clusters. An exploratory probabilistic network modeling analysis was performed to examine the statistical associations and possible mediation pathways between gut microbiota, dietary factors and stress response while adjusting for age, body mass index and blood pressure. The authors noted that other potential confounders such as physical activity, socioeconomic status, and probiotic use could not be adjusted for in this analysis.

Importantly, the study sample consisted of a majority of female participants, which may influence the generalizability of the results.

Results

Age played a hidden role: Older participants showed stronger associations between poor dietary values, altered gut bacteria and higher blood pressure in the path analysis.

The study included an average of 1,058 healthy adults aged 48.9 years. The majority of participants were female, which may affect the generalizability of the results. Hierarchical cluster analysis identified three (optimal) clusters (1–3). Clusters 2 and 3 had significantly higher and lower stress response scores, respectively, representing high stress and stress groups. Cluster 1 represented the medium stress group. Furthermore, cluster 2 had significantly lower NRF9.3 values ​​than other clusters, indicating poor diet quality.

Furthermore, cluster 2 had significantly reduced vegetable and pulse intake compared to other clusters. Researchers further examined specific foods in the FFQ and estimated individual dietary intake within nine vegetable and four impulse-based foods. They found that Cluster 2 had a significantly lower intake of green peppers, tomatoes and natto than the other clusters.

Cluster 2 also showed significantly reduced relative frequencies ofRuminococcusAndLachnospiracompared to cluster 3 andCollinsellaCompared to Cluster 1. The researchers found a statistically supported mediation path: a relationship between NRF9.3 andLachnospiraas well as in betweenLachnospiraand stress response values, but not direct effect of NRF9.3 on stress values. There was also a significant relationship between the amounts of green pepper, natto and tomatoes consumed and Nrf9.3.

Although natto is a traditional Japanese food, the authors contextualize their findings by noting that similar bioactive components can be found in globally consumed fermented foods such as tempeh or kimchi.

Conclusions

Stress clusters showed unexpected health patterns: The high-stress group had significantly lower blood pressure than the low-stress cluster—a counterintuitive finding that points to complex physiological stress adaptations.

Taken together, a higher NRF9.3 score was associated with increased relative abundanceLachnospiraand reduced points for physical and mental stress. IncreasedLachnospiraFrequency was also associated with a lower stress response. The relationship between diet quality and stress appears to be mediated byLachnospirarather than being a direct effect of diet on stress. Additionally, increased consumption of green peppers, natto, and tomatoes was associated with higher NRF9.3 levels andLachnospiraThe frequency, in turn, was associated with reduced stress response scores.

Limitations of the study include the self-reported nature of eating habits and dietary intake, possible selection bias associated with a health-conscious, predominantly female Japanese sample, poor generalizability to other populations, limited adjustment for confounders, and the use of a subjective assessment of stress (BJSQ) rather than objective biomarkers. The cross-sectional design also prevents conclusions about causality between diet, gut microbiota and stress. Additional longitudinal studies are needed to determine whether specific dietary components influence the stress response through modulation of the gut microbiota.

The authors note that natto, tomatoes, and green peppers were identified in this Japanese cohort, similar bioactive components are present in other foods consumed globally, and broader dietary patterns rich in polyphenols, fiber, and fermented foods may also be relevant to stress regulation.

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