Natto for Gut Health

Research suggests that natto and its constituent microorganisms may offer benefits for gut health, based on a small body of evidence that is generally supportive in direction but limited in study type and scope. A 2025 systematic narrative review of 125 human clinical studies on ethnic fermented foods found associations between foods like natto and improvements in gut health, immune function, and metabolic markers, though the review was broad in scope and did not isolate natto-specific findings. A 2023 laboratory and animal study identified Bacillus subtilis DG101, a bacterium native to natto, as a promising probiotic candidate that survived simulated digestive conditions, colonized the gut in animal models, and demonstrated antimicrobial properties, though human clinical trials confirming these effects are still lacking. A third study from 2022 examined gut microbiome diversity and mental health in postpartum women in Japan, where natto consumption is common, but this study did not directly investigate natto and should be interpreted as contextually related rather than directly supporting its gut health effects. Overall, the available evidence is preliminary and largely based on non-randomized or preclinical research, meaning stronger human trials would be needed before firm conclusions can be drawn.