What foods have nattokinase naturally?

If you are hunting for a list of foods packed with nattokinase, the honest answer is short — there is really only one.

Nattokinase is made by a single bacterium, Bacillus subtilis var. natto, during the fermentation of soybeans into natto, the traditional Japanese fermented-soybean food from which the enzyme was first isolated. A 50-gram serving of natto delivers roughly 1,500 fibrinolytic units — close to the 2,000 units used in most clinical trials — but eating it for the enzyme comes with a catch worth understanding first.

Table of Contents

• The Short Answer: Natto Is the Only Real Source
• Why Tempeh, Miso, and Tofu Don't Count
• How Much Nattokinase Is Actually in Natto?
• The Vitamin K2 Catch
• Nattokinase Is Fragile: Heat and Stomach Acid
• What the Clinical Trials Actually Used
• BioAbsorb Nattokinase: The Enzyme Without the K2 Load
• Frequently Asked Questions
• The Bottom Line
• Research References

The Short Answer: Natto Is the Only Real Source

Nattokinase does not occur in raw soybeans, in spinach, or in any unfermented ingredient. It appears only after boiled soybeans are fermented with one specific bacterium — Bacillus subtilis var. natto — which secretes the enzyme as it breaks down soy protein. The result is natto: a sticky, strong-smelling breakfast staple in Japan, and the single food that carries this enzyme in any meaningful amount.

Chemically, nattokinase is a serine protease of about 275 amino acids and 27.7 kilodaltons, closely related to the industrial enzyme subtilisin. Its claim to fame is fibrinolytic activity — it helps break down fibrin, the mesh protein that holds blood clots together. That property is what moved it from a regional food curiosity to one of the most-studied fibrinolytic supplements, with the standard research dose set at 2,000 fibrinolytic units, roughly 100 milligrams of extract.

So when a "top foods for nattokinase" list includes edamame, soy milk, or tofu, it is simply mistaken. None of those are fermented with B. subtilis var. natto, so none contain the enzyme. The rest of this article explains why the usual alternatives don't count, how much you actually get from natto, and the trade-off most food lists never mention.

Why Tempeh, Miso, and Tofu Don't Count

Fermentation is not one single process — it depends entirely on which microbe is doing the work. Tempeh is fermented with the mold Rhizopus oligosporus. Miso and soy sauce rely on Aspergillus oryzae (koji) together with yeasts and lactic-acid bacteria. Tofu and soy milk are not fermented at all. Each produces its own enzymes and compounds, but only natto's B. subtilis fermentation yields the enzyme we call nattokinase.

The clearest real-world evidence comes from diet research. In the Takayama cohort of 29,079 Japanese adults followed for 16 years, higher natto intake was associated with lower cardiovascular death — yet that protective association did not appear for total soy protein or for soy isoflavones from non-natto soy foods. Whatever natto is doing, the other soy foods in the same study were not doing it.

One honest caveat: a handful of other traditional Asian foods fermented with Bacillus species — such as Korean cheonggukjang or Chinese douchi — can contain related fibrinolytic enzymes. But these are uncommon outside Asia, are not standardized for enzyme activity, and vary widely from batch to batch. For practical purposes, if you want dietary nattokinase, you want natto.

How Much Nattokinase Is Actually in Natto?

Here is where food actually holds up reasonably well. A standard 50-gram serving of natto provides about 1,500 fibrinolytic units of nattokinase. The most-cited clinical dose is 2,000 FU per day, so a single pack gets you roughly three-quarters of the way there. To match 2,000 FU exactly, you would need about 65 to 70 grams — a pack and a bit.

The gap widens at higher doses. Some cardiovascular studies have used far more — up to 10,800 FU per day, taken safely for a year in one Chinese trial. Reaching that from food alone would take roughly 360 grams of natto every day, or seven to eight packs — a quantity almost nobody eats. For a standard maintenance dose, food is realistic; for the higher research doses, it is not.

There is also a consistency problem. Unlike a capsule, which is standardized to a labelled FU value, the enzyme content of natto shifts with the soybean, the bacterial strain, the fermentation time, and storage. Two packs from different brands can differ substantially, and nothing on the package tells you the fibrinolytic activity. You are getting the enzyme — just not a known dose.

The Vitamin K2 Catch

This is the part most "foods with nattokinase" articles skip. The same fermentation that produces nattokinase also produces a large amount of vitamin K2, specifically the long-lasting MK-7 form. Natto is, in fact, the richest dietary source of vitamin K2 on the planet. A peer-reviewed analysis measured 285 to 1,221 micrograms of MK-7 per 100 grams of natto — meaning a single 50-gram pack can carry anywhere from about 140 to 600 micrograms.

To put that in perspective, the adequate intake for vitamin K is only 120 micrograms a day for men and 90 for women. One pack of natto can deliver several times that — overwhelmingly as MK-7, which has a notably long half-life and lingers in the body. For most healthy people, more K2 is fine, and may even support bone and arterial health. But it is a genuine problem for one specific group.

That group is people on warfarin and other vitamin K antagonists. Vitamin K directly opposes how these drugs work, which is why clinicians advise keeping vitamin K intake steady at recommended levels rather than eating large, variable amounts. Ironically, that is the exact population most drawn to nattokinase for its clot-related effects. Eating natto to get the enzyme also hands them a K2 dose that can destabilize their medication — which is why some supplements, including BioAbsorb's K2-free Nattokinase Enzyme, remove the vitamin entirely. It is worth being precise, though: vitamin K promotes clotting and partly counteracts nattokinase's own clot-dissolving activity, so a K2-free extract gives cleaner, more predictable dosing but still calls for medical guidance for anyone on blood thinners.

Nattokinase Is Fragile: Heat and Stomach Acid

Even if you eat natto, whether the enzyme survives depends on how you treat it. Nattokinase is a protein enzyme, and enzymes are sensitive to heat and acid. It stays active up to about 50°C (122°F) but is inactivated by higher heat and by acidic conditions. Traditional natto is eaten unheated or only lightly warmed for exactly this reason — stir it into very hot rice or cook it, and you degrade some of the very enzyme you are after.

The bigger obstacle is your own stomach. Gastric acid sits well below the pH at which nattokinase remains active, so a meaningful share of what you swallow can be denatured before it reaches the small intestine, where absorption happens. This is the same challenge supplement makers face, which is why higher-quality nattokinase products use delayed-release capsules designed to carry the enzyme past the stomach intact.

The practical takeaway: natto is a live-enzyme food that rewards eating it fresh and unheated, and even then, stomach acid takes a cut. There is nothing wrong with that — it is simply a reason the casual "eat natto for nattokinase" advice is less precise than it sounds.

What the Clinical Trials Actually Used

If natto already contains nattokinase, why do studies use capsules? Because a trial needs a known, repeatable dose — and that means standardized extract, not food. The first randomized controlled trial gave 86 adults with early hypertension 2,000 FU of nattokinase daily for eight weeks, and the treated group saw systolic pressure fall by 5.55 mmHg and diastolic by 2.84 mmHg versus controls. We break these blood-pressure trials down in detail in our guide to nattokinase and blood pressure.

A North American trial is even more relevant to the food-versus-supplement question, because it deliberately used a nattokinase extract with the vitamin K2 removed. Across 74 participants taking 100 mg daily for eight weeks, diastolic pressure dropped from 87 to 84 mmHg overall — and from 86 to 81 mmHg in men — while a clot-related risk marker, von Willebrand factor, fell about 15%. That study is essentially the controlled version of eating natto, minus the K2 load.

None of this means capsules are automatically superior to food. Natto is a genuinely nutritious whole food with fibre, protein, and probiotics that a supplement doesn't provide. It means that if your goal is a specific, measured dose of the enzyme, the clinical evidence was built on standardized extract — and that is the most reliable way to reproduce it.

BioAbsorb Nattokinase: The Enzyme Without the K2 Load

The vitamin K2 problem is exactly the gap a well-designed supplement can close, and it is the reasoning behind BioAbsorb Nattokinase Enzyme. Each capsule delivers 100 mg of natto-derived nattokinase standardized to 2,000 fibrinolytic units — the same activity used in the landmark blood-pressure trial — with the vitamin K2 intentionally removed. That means you get the fibrinolytic enzyme without the several-hundred-microgram K2 dose that comes with every pack of natto, which matters most for readers already taking K2 or watching their vitamin K intake.

Two other design choices address the fragility problem from earlier. The enzyme is housed in a DRcaps delayed-release vegetarian capsule that shields it from stomach acid and carries it to the small intestine, without the phthalates and plasticizers found in some enteric coatings. And every batch is third-party tested to confirm at least 2,000 FU of activity, along with screening for heavy metals, gluten, and microbial contaminants — so the number on the label reflects what is actually in the capsule.

It is manufactured in a GMP-certified Canadian facility, is non-GMO, and is free of gluten, nuts, eggs, dairy, fish, shellfish, and all animal products. At the 180-capsule size it works out to roughly $0.28 per day for a single daily capsule taken on an empty stomach — a straightforward way to get a known dose of the enzyme that, in food, only natto provides.

Frequently Asked Questions

Does tofu, edamame, or soy milk contain nattokinase?

No. Nattokinase is created only when soybeans are fermented with Bacillus subtilis var. natto, and tofu, edamame, and soy milk are not fermented with that bacterium — tofu and soy milk are not fermented at all. They offer soy protein and isoflavones, but no nattokinase.

Can I get enough nattokinase from eating natto instead of a supplement?

You can get a meaningful amount — about 1,500 FU per 50-gram pack, close to the standard 2,000 FU dose. The catches are that the FU content of food is variable and unlabelled, and each pack also delivers several hundred micrograms of vitamin K2, which is a concern if you take blood thinners.

How much natto equals a 2,000 FU supplement?

Roughly 65 to 70 grams, or a little over one standard pack. To reach the higher doses used in some cardiovascular studies — up to 10,800 FU — you would need around 360 grams per day, which is impractical for most people. Our nattokinase dosage guide breaks down how the standard and higher doses are actually used.

Does cooking natto destroy the nattokinase?

High heat does. The enzyme stays active only up to about 50°C (122°F), so natto is traditionally eaten unheated or barely warmed. Stirring it into very hot food or cooking it degrades some of the enzyme.

Is nattokinase the same thing as vitamin K2?

No — they are two different substances that both form during natto fermentation. Nattokinase is a fibrinolytic enzyme; vitamin K2 (MK-7) is a fat-soluble vitamin involved in blood clotting and bone health. A supplement can contain one without the other.

Is natto or a nattokinase supplement safer if I take warfarin?

Neither should be started without medical advice. Natto's high vitamin K2 content can directly interfere with warfarin, and nattokinase itself may increase bleeding risk alongside anticoagulant or antiplatelet drugs. Talk with your doctor before using either.

The Bottom Line

The list of foods that naturally contain nattokinase begins and ends with natto, which delivers a meaningful ~1,500 FU per pack alongside a vitamin K2 dose that not everyone wants. If you enjoy natto, it is a genuinely nutritious food worth eating; if you want the fibrinolytic enzyme at a standardized dose without the K2, a K2-free option like BioAbsorb Nattokinase Enzyme is the more predictable route. Either way, check with your doctor first if you take blood thinners or have a bleeding condition.

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). First isolation of nattokinase from natto and identification of Bacillus subtilis var. natto as the producing organism.
2. Effects of nattokinase on blood pressure: a randomized, controlled trial. Hypertension Research, Vol. 31 (2008). In 86 adults with pre- or stage-1 hypertension, 2,000 FU/day for 8 weeks reduced systolic pressure by 5.55 mmHg and diastolic by 2.84 mmHg versus control.
3. Consumption of nattokinase is associated with reduced blood pressure and von Willebrand factor, a cardiovascular risk marker: results from a randomized, double-blind, placebo-controlled, multicenter North American clinical trial. Integrated Blood Pressure Control, Vol. 9 (2016). Used K2-removed nattokinase (100 mg/day, 8 weeks); diastolic pressure fell 87→84 mmHg overall and 86→81 mmHg in men, with a ~15% drop in von Willebrand factor.
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). In 29,079 adults over 16 years, the highest quartile of natto intake was associated with lower total CVD mortality (HR 0.75) and ischemic stroke mortality (HR 0.67); no such association was seen for other soy foods.
5. A simultaneous determination and monitoring of vitamin K1 (phylloquinone) and vitamin K2 (menaquinone) in vegetable drinks and natto sold on the Korean market. Journal of Food Measurement and Characterization, Vol. 16, pp. 248–257 (2022). Measured MK-7 content in natto at 285–1,221 mcg per 100 g, with frozen products 2–4 times higher than refrigerated.
6. Vitamin K: Fact Sheet for Health Professionals. National Institutes of Health, Office of Dietary Supplements. Reports the Adequate Intake for vitamin K as 120 mcg/day for men and 90 mcg/day for women.
7. Vitamin K. Linus Pauling Institute, Oregon State University. Advises that people taking vitamin K antagonists such as warfarin keep vitamin K intake reasonably constant at recommended levels (90–120 mcg/day).
8. Nattokinase (professional monograph). Drugs.com. Notes that a 50 g serving of natto provides about 1,500 FU of nattokinase, that the enzyme is stable to about 50°C but inactive in acidic conditions, and that vitamin K2 is co-produced during fermentation and can be removed from supplements.
9. Nattokinase. Examine.com. Summarizes the standard dose of 2,000 FU (~100 mg) daily and higher doses of up to 10,800 FU/day used safely in studies.

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.