What foods contain nattokinase?

Type "foods that contain nattokinase" into a search bar and you will get long lists — nearly all of them wrong.

The honest answer is short: one traditional Japanese food, natto, is the only common food that actually contains this clot-dissolving enzyme, first identified in 1987. Everything else on those lists either uses the wrong fermentation or contains no nattokinase at all — and even natto carries a catch worth understanding before you reach for chopsticks or a capsule.

Table of Contents

• The Short Answer: Natto Is the Only Food That Truly Contains Nattokinase
• Why Tofu, Tempeh, Miso, and Soy Sauce Don't Count
• The Close Cousins: Other Bacillus-Fermented Foods
• How Much Natto Would You Actually Need?
• The Vitamin K2 Catch Hiding in Natto
• Food or Supplement: How to Decide
• A Standardized, K2-Free Way to Get Nattokinase
• Frequently Asked Questions
• Conclusion

The Short Answer: Natto Is the Only Food That Truly Contains Nattokinase

If you want nattokinase from food, there is one realistic option: natto, a sticky, strong-smelling Japanese breakfast dish made from soybeans fermented with the bacterium Bacillus subtilis var. natto. The enzyme was first isolated from natto in 1987 by Dr. Hiroyuki Sumi, who measured an average fibrinolytic activity of roughly 40 units per gram of wet natto. It is a subtilisin-like serine protease that was later purified and characterized in detail, and its entire claim to fame is dissolving fibrin, the mesh protein that holds blood clots together.

The single most important thing to understand is this: nattokinase is a product of the bacterium, not of the soybean. The same Bacillus subtilis fermentation that creates natto's slippery texture is what synthesizes the enzyme. No Bacillus subtilis fermentation, no nattokinase.

That one fact explains why the enzyme's food footprint is so narrow. Interest in it is not narrow, though: in a Japanese population study of nearly 29,000 adults followed for 16 years, the people eating the most natto had a 25% lower risk of dying from cardiovascular disease, an association that did not appear for soy protein or soy isoflavones generally.

Why Tofu, Tempeh, Miso, and Soy Sauce Don't Count

Most "nattokinase foods" lists pad themselves out with other soy products, but the microbiology rules them out. Fermentation is defined by the specific organism doing the work, and only one organism makes nattokinase. According to fermented-food guidance from the BC Centre for Disease Control, the common soy ferments each rely on a different starter culture.

• Tempeh is fermented by a mold, Rhizopus, not a bacterium — a 2026 review confirms this mold-driven process differs fundamentally from natto's.
• Miso and soy sauce are made with koji mold (Aspergillus oryzae), which produces umami and its own enzymes — but no nattokinase.
• Tofu, edamame, soy milk, and roasted soybeans are not fermented by Bacillus subtilis at all, so there is no route for the enzyme to form.

The takeaway is simple: sharing "soy" as an ingredient tells you nothing about nattokinase content. Two foods can start from the same bean and end up completely different, because the roughly 24-hour fermentation with Bacillus subtilis is what defines natto — and it is the only one of these four processes that yields the enzyme. Anyone eating tofu or miso for its clot-dissolving effect is eating a healthy food for the wrong reason.

The Close Cousins: Other Bacillus-Fermented Foods

There is one honest nuance. Because the enzyme comes from Bacillus fermentation, a handful of other traditional foods across Asia — fermented with related Bacillus strains — contain similar fibrinolytic enzymes. A 2019 study in Scientific Reports isolated one such enzyme, a 29 kDa serine protease, from Chinese douchi, and notes comparable enzymes have been reported in doenjang, cheonggukjang, and other regional ferments.

• Cheonggukjang (Korean fast-fermented soybean paste) — made with Bacillus strains that produce their own fibrinolytic enzymes.
• Douchi (Chinese fermented black soybeans) — the source of the DFE27 enzyme characterized in the 2019 study.
• Doenjang (Korean soybean paste) — another traditional Bacillus ferment reported to contain fibrinolytic activity.

Two honest caveats keep this from being a loophole. First, these are not nattokinase — they are different, related enzymes, and their fibrinolytic strength and consistency vary by strain and batch. Second, these foods are hard to find, and harder to standardize, outside their home regions. So while it is fair to say the wider family of Bacillus-fermented soy foods carries clot-related enzymes, natto remains the only widely available food specifically studied as the source of nattokinase.

How Much Natto Would You Actually Need?

Say you are willing to eat natto for its enzyme. The next problem is dose. The original 1987 work put natto's activity at about 40 fibrinolytic units per gram, but that figure sits on top of a real inconsistency: the enzyme's activity in food shifts with the soybean, the specific Bacillus strain, the fermentation time, and storage. A container of natto is not labeled with a guaranteed enzyme content the way a tablet is.

That matters because the human research uses standardized doses. The most-cited blood pressure trial gave participants a fixed 2,000 FU dose daily for 8 weeks — a defined, repeatable amount. Nattokinase is a potent fibrinolytic enzyme, but that potency only translates into a reliable effect if the dose is reliable.

So the practical answer to "how much natto?" is not a tidy number of grams — it is that food cannot promise you a specific, repeatable amount of active enzyme. For an occasional health-supporting food, that variability is fine. For someone trying to hit a research-backed dose, it is the core limitation of the food-only approach.

The Vitamin K2 Catch Hiding in Natto

Here is the twist most food lists never mention. Natto is not only the best food source of nattokinase — it is also widely recognized as the single richest dietary source of vitamin K2 (menaquinone-7). That sounds like a bonus, but for one group of people it is a genuine complication, because nattokinase and vitamin K2 are entirely different compounds that pull in opposite directions on blood clotting.

Nattokinase helps break clots down. Vitamin K2, by contrast, is a cofactor the body uses to build the clotting factors II, VII, IX, and X — the same four factors that the drug warfarin is designed to suppress. As a professional drug reference notes, the high vitamin K2 in natto can reduce the INR in people taking warfarin, working against their medication and potentially raising clot risk — and that same reference flags that the interaction can carry over to supplements unless the K2 is removed during production.

For most healthy people, natto's vitamin K2 is a plus, not a problem. But if you are on warfarin or another anticoagulant, this single food combines a clot-dissolving enzyme with a large dose of a clot-supporting vitamin — which is exactly why anyone in that situation should talk to their doctor before adding natto, and why a nattokinase source without vitamin K2 can be the more predictable option.

Food or Supplement: How to Decide

Once you know natto is the only real food source, the choice becomes practical rather than mysterious. Whole natto delivers nattokinase inside a genuinely nutritious package — protein, fiber, probiotics, and vitamin K2 — and the population data tie regular natto intake to a 25% lower cardiovascular death risk. If you enjoy it and are not on a blood thinner, eating it is a reasonable, evidence-supported choice.

For many people outside Japan, though, three barriers stack up: the strong ammonia-like smell and slippery texture are an acquired taste, fresh natto is hard to buy in most Western grocery stores, and — as covered above — the enzyme content is not standardized. A supplement is designed to solve those specific problems by delivering a defined 2,000 FU dose in a form you can take in seconds — the same dose a 2023 meta-analysis of six randomized trials linked to consistent blood-pressure reductions — and it can leave out the vitamin K2 that complicates things for anticoagulant users.

Neither route is a treatment for any medical condition, and neither should replace prescribed medication. The realistic framing is: natto if you love it and tolerate it well, a standardized supplement if you want a consistent dose without the taste, the sourcing hassle, or the K2.

A Standardized, K2-Free Way to Get Nattokinase

This is the gap BioAbsorb Nutraceuticals' Nattokinase Enzyme is built to fill. Each capsule delivers 100 mg of nattokinase standardized to 2,000 FU of enzyme activity — the same dose used in the most-cited human blood pressure trial — so you get a defined amount every time instead of the batch-to-batch variability of food. Every batch is third-party tested to confirm it meets that 2,000 FU potency, along with checks for heavy metals, gluten, and microbial contaminants.

Two design choices speak directly to the issues raised in this article. First, it is intentionally free of vitamin K2 — sidestepping the warfarin complication that natto's naturally high K2 creates (though anyone on an anticoagulant should still clear any new supplement with their physician). Second, it uses a DRcaps delayed-release vegetarian capsule that helps protect the enzyme from stomach acid without the phthalates and plasticizers found in some enteric coatings. It is non-GMO, made in a Canadian GMP-certified facility, and free of gluten, nuts, eggs, dairy, fish, shellfish, and all animal products. The routine is one capsule daily on an empty stomach.

Frequently Asked Questions

Can you get nattokinase from any food besides natto?

Not in any practical, widely available way. Nattokinase is produced only during fermentation by Bacillus subtilis var. natto, which is what makes natto; a few related Bacillus-fermented foods like douchi and cheonggukjang contain similar but distinct fibrinolytic enzymes, not nattokinase itself.

Does tempeh or miso contain nattokinase?

No. Tempeh is fermented by a Rhizopus mold and miso by Aspergillus koji mold, and neither organism produces nattokinase. They are healthy fermented foods, but not sources of this particular enzyme.

How much natto equals a 2,000 FU supplement?

There is no reliable equivalent, because natto's enzyme activity is not standardized and varies with the strain, fermentation, and storage. The original research measured about 40 fibrinolytic units per gram, but a container is never labeled with a guaranteed amount — which is precisely why the clinical trials use standardized capsules.

Is it safe to eat natto if I take a blood thinner?

Check with your doctor first. Natto is extremely high in vitamin K2, which can reduce the INR and work against warfarin, while nattokinase itself may add to bleeding risk with anticoagulant or antiplatelet drugs. This combination is the main reason natto and nattokinase warrant medical supervision for anyone on these medications.

Does cooking or heating natto destroy nattokinase?

High heat degrades the enzyme, which is why natto is eaten cold or only lightly warmed and is traditionally added to hot rice at the end rather than cooked. Nattokinase remains stable across a moderate temperature range but loses activity when heated well above body temperature, so boiling or frying natto would blunt its enzyme content.

Is natto or a nattokinase supplement better?

It depends on your goal. Natto offers a nutrient-dense whole food linked to a 25% lower cardiovascular death risk in population studies, while a supplement offers a consistent, K2-free 2,000 FU dose without the taste or sourcing challenges — and neither is a substitute for medical care.

Conclusion

The real answer to "what foods contain nattokinase" is refreshingly simple: essentially one food, natto, because the enzyme is a product of Bacillus subtilis fermentation and nothing else in the soy aisle is made the same way. Natto is a genuinely healthy choice for those who enjoy it, but its unstandardized enzyme content and very high vitamin K2 make it an imperfect delivery system — especially for anyone on a blood thinner. If you want a defined, K2-free 2,000 FU dose without the acquired taste, explore BioAbsorb's third-party-tested Nattokinase Enzyme and talk with your healthcare provider about whether it fits your needs.

For related reading, see what natto is and where it comes from, whether food sources provide enough nattokinase, and the complete guide to nattokinase.

Research References

1. A novel fibrinolytic enzyme (nattokinase) in the vegetable cheese Natto; a typical and popular soybean food in the Japanese diet. Experientia, Vol. 43 (1987), pp. 1110–1111. First isolation of nattokinase from natto and the origin of the enzyme's name; measured average fibrinolytic activity in natto.
2. Purification and characterization of a strong fibrinolytic enzyme (nattokinase) in the vegetable cheese natto, a popular soybean fermented food in Japan. Biochemical and Biophysical Research Communications, Vol. 197 (1993), pp. 1340–1347. Purification and biochemical characterization of nattokinase as a potent subtilisin-family serine protease.
3. Effects of nattokinase on blood pressure: a randomized, controlled trial. Hypertension Research, Vol. 31 (2008), pp. 1583–1588. Randomized, double-blind, placebo-controlled trial in which a standardized 2,000 FU daily dose reduced systolic and diastolic blood pressure over 8 weeks.
4. Dietary soy and natto intake and cardiovascular disease mortality in Japanese adults: the Takayama study. The American Journal of Clinical Nutrition, Vol. 105 (2017), pp. 426–431. Population cohort of nearly 29,000 adults linking the highest natto intake to lower cardiovascular mortality, with no equivalent effect for soy protein or isoflavones.
5. Purification and characterization of a novel, highly potent fibrinolytic enzyme from Bacillus subtilis DC27 screened from Douchi, a traditional Chinese fermented soybean food. Scientific Reports, Vol. 9 (2019). Documents a potent fibrinolytic enzyme (DFE27) in douchi, a Bacillus-fermented soybean food, showing that related clot-dissolving enzymes occur in Bacillus ferments beyond natto.
6. Nattokinase Supplementation and Cardiovascular Risk Factors: A Systematic Review and Meta-Analysis of Randomized Controlled Trials. Reviews in Cardiovascular Medicine, Vol. 24, No. 8 (2023). Pooled analysis of six randomized trials (546 participants) finding statistically significant reductions in systolic and diastolic blood pressure versus placebo.
7. Unraveling Tempeh through omics: a scoping review of fermentation pathways and functional health benefits. npj Science of Food, Vol. 10 (2026). Confirms tempeh is fermented primarily by Rhizopus mold, a fundamentally different process from natto's Bacillus fermentation.
8. Nattokinase. Drugs.com Professional Natural Products Monograph (2026). Clinical reference describing how natto's high vitamin K2 can reduce INR in patients on warfarin and how this may extend to supplements that retain K2.
9. Fermented Foods Guideline — Koji and Miso (Section 3.10). BC Centre for Disease Control, Government of British Columbia. Government reference outlining the distinct starter cultures used for natto (Bacillus), tempeh (Rhizopus), and miso and soy sauce (Aspergillus).

About the Author

David Kimbell is a health writer, digital entrepreneur and former aerospace engineer, based in Ottawa, Canada. He loves translating complex science into clear, actionable guidance for consumers seeking evidence-based solutions.

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Important Disclaimers

Medical Disclaimer: This article provides educational information only and is not intended as medical advice. Always consult with a qualified healthcare provider before starting any new supplement, especially if you have existing health conditions, take medications, or are pregnant or nursing.

FDA/Health Canada Statement: These statements have not been evaluated by the Food and Drug Administration or Health Canada. This product is not intended to diagnose, treat, cure, or prevent any disease.