New evidence
A meta-analysis of Japanese studies linked habitual natto intake to modestly greater bone density (d = 0.65) — but the certainty of the evidence was low, and nearly all data came from observational research.
This is the first systematic review on natto and bone density, but because it mostly pools observational studies with moderate-to-low certainty, think of it as a suggestive signal — not a settled finding — that needs confirmation in controlled trials.
People who regularly ate natto showed slightly higher bone mineral density (an effect size around 0.35–0.65 depending on the analysis) and had better vitamin K status, as measured by higher MK-7 levels and improved osteocalcin carboxylation — a protein marker that helps calcium bind to bone. However, the evidence is based largely on observational studies (not randomized experiments), so it's unclear whether the natto itself caused the benefit or whether other lifestyle factors explain the link.
Where this fits in the evidence
This is among the first studies we've indexed on natto for Increased Bone Mineral Density — treat it as an early signal until more research accumulates.
The study
- Systematic Review
- 2025-11-28
- Frontiers in nutrition
This is a plain-language summary of a research finding, not medical advice. Pillser surfaces research signals to help you decide what's worth investigating — always consult a qualified professional before changing what you take.