Evidence on Atrial Fibrillation and Mortality Risk
In recent years, growing scientific attention has been given to the health effects of soy-based foods, including natto. Among these, potential associations with cardiovascular disease (CVD) and cardiac arrhythmias have been explored in several population-based studies.
This article reviews recent and prior epidemiological research examining whether natto consumption is associated with a reduced risk of atrial fibrillation and cardiovascular disease–related mortality.
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納Does Natto Reduce the Risk of Atrial Fibrillation?
A recent study conducted by researchers at the National Cerebral and Cardiovascular Center of Japan investigated the relationship between soy food intake and the risk of developing atrial fibrillation.
The findings indicated that higher natto and vitamin K intake were associated with a lower risk of atrial fibrillation in women, while no significant association was observed in men.
Specifically:
Women with the highest natto intake had a 56% lower risk of atrial fibrillation compared with those with the lowest intake.
Women with the highest vitamin K intake showed a 67% lower risk of atrial fibrillation.
What Is Atrial Fibrillation? Atrial fibrillation is a type of cardiac arrhythmia characterized by irregular and rapid electrical activity in the atria of the heart. While it does not typically cause sudden cardiac death like ventricular fibrillation, it is a major risk factor for ischemic stroke and other cardiovascular complications, making it a significant public health concern.
Study Design and Methods
This investigation was a prospective cohort study involving 5,278 Japanese men and women aged 30 to 90 years living in urban areas.
At baseline:
Dietary intake was assessed using a food frequency questionnaire.
Intake levels of natto, miso, soy sauce, soybeans, soy isoflavones, and vitamin K were estimated.
Participants were categorized into three groups based on intake levels: highest, intermediate, and lowest.
Participants were followed for an average of 12.6 years, and atrial fibrillation cases were identified using:
Electrocardiogram findings
Health examinations
Medical records
Death certificates
Key Findings by Sex
Among women:
Higher natto intake was associated with a substantially lower risk of atrial fibrillation.
Higher vitamin K intake showed a similar inverse association.
Among men:
No meaningful association was found between natto or vitamin K intake and atrial fibrillation risk.
Importantly, for both men and women, no significant association was observed between atrial fibrillation risk and intake of:
Total soy foods
Tofu
Whole soybeans
Soy isoflavones
These findings were published in the January 2026 issue of The Journal of Nutrition.
Unit of meassurement
Women
Men
Natto intake (highest vs. lowest)）
Atrial fibrillation risk: 56% Reduction
3% reduction (not related)）
Vitamin K intake (Highest vs. Lowest)
Atrial Fibrillation Risk: 67% Reduction
Not Related
Total soy food intake
Not Related
Not Related
Tofu intake
Not Related
Not Related
Soybean intake
Not Related
Not Related
Isoflavone intake
Not Related
Not Related
Association between Natto and Vitamin K Intake and Atrial Fibrillation Risk (by Gender)
These results were published in the January 2026 issue of The Journal of Nutrition.
Association between Intake of Natto, Soy Protein, Soy Isoflavones and Cardiovascular Disease Mortality
Additional evidence comes from the well-known Takayama Study, a long-running cohort study initiated in 1992 by a research team at Gifu University.
This study aimed to clarify the relationship between dietary habits and long-term health outcomes, including cause-specific mortality, among residents of Takayama City, Japan.
Study Population and Scope
The analysis included 29,079 adults aged 35 years and older (13,355 men and 15,724 women).
Researchers examined associations between intake of:
Natto
Soy protein
Soy isoflavones
and mortality from cardiovascular disease, including stroke and ischemic heart disease.
During the follow-up period:
1,678 deaths were documented
677 were due to stroke
308 were due to ischemic heart disease
What Did the Takayama Study Find?
Participants with the highest natto intake showed a 25% lower risk of all-cause mortality compared with those with the lowest intake.
When analyzed by disease category:
Stroke-related mortality was 32% lower among high natto consumers.
Mortality from ischemic stroke was 33% lower in the highest natto intake group.
In contrast:
Soy protein and soy isoflavone intake alone did not show a consistent association with overall cardiovascular mortality.
These results were published in the December 7, 2016 issue of The American Journal of Clinical Nutrition.
Association between natto intake and mortality risk
Unit of meassurement
Results (highest vs. lowest intake group)
Total mortality risk
25% reduction
Death from stroke
32% reduction
Death from ischemic stroke
33%reduction
Association Between Soy Component Intake and Mortality Risk
Item / Category
Outcome / Disease
Results (Highest vs. Lowest Intake)
Soy Protein
Total Cardiovascular Disease (CVD)
No significant association
Stroke Mortality
25% reduction
Soy Isoflavones
Total Cardiovascular Disease (CVD)
No significant association
These results were published in the December 7, 2016, issue of The American Journal of Clinical Nutrition.
What Is a Prospective Cohort Study?
A prospective cohort study follows a defined group of individuals over time, starting from a baseline assessment, to compare disease incidence or mortality rates based on exposure levels (such as dietary intake). This design is commonly used to identify associations between lifestyle factors and health outcomes.
Should You Include Natto in Your Diet?
Taken together, these studies suggest that natto consumption may be associated with favorable cardiovascular health indicators, particularly in relation to atrial fibrillation and stroke-related mortality.
While these findings do not establish causation, they indicate that including natto as part of a balanced dietary pattern may be a reasonable option for individuals considering evidence-based dietary choices.
Notably, several studies highlight the potential role of spore-forming natto bacteria, which may contribute to natto’s unique biological properties.
