Lower risk of depression may be tied to diet of Japanese food

Asahi Shimbun

5 days ago

A study's take on an improved version of a typical Japanese meal adds a glass of milk, switches white rice for brown rice and swaps pickled vegetables and plums with raw vegetables and fruit. (Kenji Tamura)
A research team at the Japan Institute for Health Security says there is a correlation between people whose meals frequently consist of traditional Japanese dishes and the trend of being less likely to develop depressive symptoms.
The team reached this conclusion after surveying about 12,500 employees across five companies headquartered in the Kanto and Tokai regions between fiscal 2018 and fiscal 2020.
Respondents answered questions about their lifestyle habits such as alcohol consumption and sleep patterns, as well as how often and what type of food and dishes they usually consume.
NO SINGLE CURE-ALL DISH
The research team then created a 'traditional Japanese food score' based on the questionnaire's answers.
Individual respondents received higher scores if their diet frequently featured white rice, miso soup, soy-based dishes, cooked vegetables, mushrooms, seaweed, fish and green tea. Salted fare in the vein of pickled vegetables and dried fish was also included.
Earlier surveys often highlighted the relationship between a single type of food and wellness, such as 'natto (fermented soybeans) is good for health.'
However, researchers are increasingly focusing instead on diet patterns and health rather than individual ingredients to more realistically account for meals consisting of multiple dishes and ingredients.
The survey addressed mental health by asking participants about 11 mood-related experiences over the past week that included "feeling down" and having "trouble sleeping."
Those who scored nine points or more were classified as having "depressive symptoms."
Participants were divided into four groups based on their traditional Japanese food scores spanning from highest to lowest. This was done in order to next examine the relationship between diet and depression.
The results showed a trend: the higher the traditional Japanese food scores, the less likely the participant was to also have depressive symptoms.
In the group with the lowest scores, 35.8 percent were classified as having depressive symptoms. In contrast, only 25.3 percent of those in the highest-scoring group fell into this category.
After statistically adjusting for differences in age, education, working overtime, alcohol consumption and sleep duration so these factors would not affect the survey results, the analysis revealed that the highest-scoring group had a 17 percent lower rate of depressive symptoms compared to the lowest-scoring group.
Folate, or vitamin B9, may be a contributing factor in the survey results. Found in seaweed, soy-based dishes and certain vegetables, it is believed to help synthesize the brain's neurotransmitters that regulate hormones and blood pressure, among other functions.
Previous studies have additionally highlighted omega-3 fatty acids that fish are rich in as supporting neurotransmitter functionality.
AN 'IMPROVED' JAPANESE MEAL
The traditional Japanese diet is not infallible, however. As a refined grain, white rice contains relatively little dietary fiber and materials.
Traditional Japanese meals also tend to lack dairy products, raw vegetables and fruit, while "tsukemono" (pickled vegetables) and dried fish tend to be high in sodium.
To address these shortcomings, the research team also developed a 'modified traditional Japanese food score.'
This new version assigns higher points for frequent consumption of less-refined grains like brown rice, as well as milk and dairy products, raw vegetables and fruit. Conversely, it gives lower scores for frequent consumption of salt-heavy dishes such as tsukemono and dried fish.
Using these modified scores to assess depressive symptoms revealed a trend similar to the results based on the traditional Japanese food scores. There was no distinct difference in the correlations observed using either score.
Since the study asked participants about their dietary patterns and depressive symptoms at the same time, further follow-up studies are needed to determine whether regularly eating Japanese food is truly tied to mental well-being.
'We'd like to conduct further research by using long-term data to investigate the relationship between dietary patterns and depression,' said Haruka Miyake, a senior researcher at Japan Institute for Health Security and a member of the research team that conducted the survey.