Mixed

The gut microbiome of healthy Japanese individuals exhibits a distinct functional profile characterized by high abundance of Actinobacteria (specifically Bifidobacterium) and a unique hydrogen metabolism pathway that favors acetogenesis over methanogenesis, which cannot be fully explained by diet alone.

This research highlights that gut microbiomes are population-specific and influenced by factors beyond just what you eat today. For Japanese individuals, a high abundance of Bifidobacterium and a preference for acetogenesis (producing acetate) over methanogenesis (producing methane) are characteristic. These features may contribute to health benefits like lower inflammation and longer lifespan, but they are deeply rooted in population-level adaptations, not just short-term dietary changes.