Fermented soy and mortality: an association, not a prescription.
A Japanese cohort study is informative, but it cannot establish that eating natto causes longer life.
By Happy Natto · Updated September 17, 2026
Illustrative editorial photograph. It is not an image from the cited study.Photo: Dr. Mohammad Hoque / Pexels
The study followed Japanese adults and reported associations between fermented-soy intake and mortality outcomes. Natto and miso were part of the fermented-soy category. It was not a randomized feeding experiment.
What it does not establish
Differences in lifestyle, diet, reporting and other factors can contribute to the association. Findings in this population do not tell an individual what will happen if they start eating natto.
How to use this entry
Open the original source for the full methods, analyses and context. The evidence label describes the type of source, not a universal score for the healthfulness of natto. We do not turn a product link into a medical recommendation.
