Interindividual Variation in Adult Gut Microbiome Composition in Two Rural Communities in Japan: Associations With...

The "Japanese diet" has long been regarded as a key factor contributing to the remarkable life expectancy of the Japanese population. Given that the gut microbiome is thought to mediate the link between diet and health, this study investigated energy and nutrient intake among rural populations in Japan, who are presumed to adhere closely to the traditional "Japanese diet," and examined their association with gut microbiome diversity and composition.

A cross-sectional study of 263 individuals aged ≥ 20 years was conducted in two rural communities in Japan, in July and August 2022. Participants completed a food frequency questionnaire, and we measured weight and height and collected fecal samples. The diversity and composition of the gut microbiome were assessed using 16S ribosomal RNA analysis. The associations between energy and nutrient intakes and alpha diversity metrics, beta diversity metrics, and the relative abundance of bacteria at the genus level were assessed.

Individuals who consumed more nutrients characteristic of seafood, rice, and vegetables (vitamin D, omega-3 highly unsaturated fatty acids, carbohydrates, total dietary fiber, and insoluble dietary fiber) had significantly higher gut microbiome diversity, while those who consumed more alcohol and fat had significantly lower microbiome diversity. Energy intake from alcohol, as well as intakes of cholesterol, iron, vitamin B1, vitamin C, carbohydrates, soluble dietary fiber, omega-3 highly unsaturated fatty acids, and calcium were significantly associated with beta diversity metrics (p < 0.05), indicating that gut microbiome composition varied with these nutrient intakes.

Nutrient intakes may influence the interindividual variation in the gut microbiome seen in two rural populations in Japan. Future research should focus on elucidating the interactive effects between the "Japanese diet" and the gut microbiome.