Bacillus subtilis natto

ProbioticBacillusBest with a meal

What is it

Bacillus subtilis var. natto is the bacterium used to ferment soybeans into natto, a traditional Japanese food. It is also the source of nattokinase, an enzyme produced during fermentation that is widely marketed as a supplement.

Evidence for 2 uses

AI-assisted evidence assessment — talk to your doctor before relying on any single supplement.

Cardiovascular support (nattokinase)

Limited Evidence

Small studies suggest possible modest effects on blood pressure and fibrinolytic markers; large outcome trials are lacking.

General probiotic / digestive support

Limited Evidence

B. subtilis spore probiotics have shown modest effects on digestive symptoms in some studies, though strain-specific evidence varies.

How it works

During fermentation, B. subtilis natto secretes nattokinase, a protease that can degrade fibrin (the protein that forms blood clots) in laboratory settings. Live B. subtilis natto also functions as a spore-forming probiotic that survives stomach acid and germinates in the small intestine. The nattokinase enzyme has been the focus of cardiovascular research for blood-clot-related conditions. Some clinical studies suggest fibrinolytic activity after oral nattokinase, but interpretation requires caution because enzyme survival after digestion is variable.

Dosage

Probiotic doses of B. subtilis natto are typically 1-2 billion CFU per day. Nattokinase products are dosed by enzyme activity (typically 2000-4000 FU/day) rather than by CFU.

When and how to take it

Probiotic forms are typically taken once daily with food. Nattokinase products are often taken on an empty stomach to maximize enzyme activity.

2 commercial forms

Compare the main delivery options and what they’re best suited for.

Bacillus subtilis natto spores

Used in probiotic capsules.

Spores survive stomach acid and germinate in the small intestine.

Nattokinase (enzyme extract)

Used in cardiovascular-focused supplements.

Activity expressed as FU; partial digestion in the gut limits the systemic dose.

Safety

B. subtilis natto and nattokinase have a strong food-safety record from natto consumption in Japan. Spore-forming bacilli are generally well tolerated. The main safety consideration with nattokinase is its potential effect on blood clotting.

Who should be cautious

Stop nattokinase before surgery (at least 1-2 weeks). Avoid in active bleeding, recent stroke, or bleeding disorders. Pregnancy and breastfeeding safety is not well established for concentrated supplements.

Interactions

Nattokinase has fibrinolytic activity and may increase the effect of anticoagulants (warfarin, DOACs), antiplatelet drugs (aspirin, clopidogrel), and NSAIDs. People on these medications should consult a clinician before use.

Food sources

Natto (fermented soybeans)

Amount
1/2 cup (100 g)
%DV
—

Frequently asked questions

Is nattokinase safer than warfarin?⌄

It is not a substitute for warfarin or other prescribed anticoagulants. People on these medications should consult a clinician before adding nattokinase due to risk of additive bleeding.

Do I need to eat natto to get the benefit?⌄

Natto delivers both live bacteria and nattokinase. Supplements provide more concentrated and standardized doses than the food.

References

Bacillus subtilis natto on NIH DSLD (US supplement label database) — NIH Dietary Supplement Label Database link

Research on Bacillus subtilis natto (PubMed search) — PubMed link

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Evidence-based·How we grade evidence

Disclaimer: These statements have not been evaluated by the FDA. This page is educational, not a substitute for personalized medical advice. Evidence grades are AI-assisted assessments — talk to your doctor before starting any new supplement, especially if you’re pregnant, breastfeeding, on medications, or managing a chronic condition.