Nattokinase Benefits (Natto)

Short answer: Nattokinase is a serine protease enzyme extracted from natto, the traditional Japanese fermented soybean food. Small human studies suggest it can produce modest reductions in blood pressure and improvements in some lipid and clotting parameters at typical supplement doses of 100 to 200 mg (about 2,000 to 4,000 fibrin units) per day⁽¹⁾. It is not a substitute for prescribed cardiovascular medications, and it carries a real bleeding-risk interaction with warfarin, DOACs, aspirin, and other antiplatelet drugs.

This guide covers what nattokinase is, what the human evidence actually shows, who should not take it, and how to use it more safely if your clinician approves.

What nattokinase actually is

Natto is a Japanese food made by fermenting boiled soybeans with the bacterium Bacillus subtilis var. natto. During fermentation, the bacterium secretes a range of enzymes, one of which is nattokinase, a serine protease that can break down fibrin, the main protein in blood clots, in laboratory assays. Nattokinase was isolated and named by researcher Hiroyuki Sumi in 1980, who observed that a drop of the sticky natto substance dissolved a fibrin clot in a petri dish.

Two important distinctions:

• Nattokinase is the isolated enzyme, sold as a supplement in capsule or tablet form and dosed in fibrin units (FU).
• Natto is the whole fermented soybean food, which contains nattokinase along with vitamin K2 (menaquinone-7), fiber, plant protein, probiotic bacteria, and other compounds.

Health claims about “natto” and about “nattokinase supplements” are not the same thing. Most of the strongest data are for either the whole food or for standardized enzyme preparations, and effects should not be assumed to transfer freely between them.

Standard supplement dosing

Commercial nattokinase is measured in fibrin units (FU), a laboratory activity measure. Typical products deliver:

• 100 mg = about 2,000 FU
• 150 mg = about 3,000 FU
• 200 mg = about 4,000 FU

Most human trials that show an effect use 2,000 to 4,000 FU per day, taken as one or two doses.

What the human evidence actually shows

Blood pressure

Several small randomized trials have tested nattokinase in adults with pre-hypertension or mild hypertension. A meta-analysis by Chen and colleagues published in 2018 combined the available data and reported small but statistically meaningful reductions in systolic and diastolic blood pressure with nattokinase supplementation compared with placebo, on the order of 3 to 5 mmHg⁽¹⁾. Effects were more consistent in adults with higher baseline pressures. These reductions are real but modest, less than what a first-line antihypertensive medication typically achieves, and should not be used as a substitute for prescribed therapy in diagnosed hypertension.

Lipids

Some small trials have reported reductions in total cholesterol, LDL cholesterol, and triglycerides with nattokinase, often combined with statin therapy or with a plant-based diet. Effect sizes vary and the trials are small. Nattokinase is not a replacement for statin therapy in people who need it.

Clot dissolution and stroke prevention

The mechanism most often cited is that nattokinase enhances fibrinolysis, the body’s natural clot-breakdown process, by activating plasmin-related pathways and directly cleaving fibrin. Laboratory assays show this activity clearly. Whether that translates into reduced stroke or heart attack rates in humans has not been established by large outcome trials. Do not take nattokinase as a stroke- or heart-attack-prevention drug in place of aspirin, statins, or anticoagulants prescribed for that purpose.

Post-thrombotic syndrome and deep vein thrombosis

Small studies suggest nattokinase may help symptoms of chronic venous insufficiency and mild leg swelling, but again the evidence is preliminary. It is not a substitute for evaluation of new-onset leg swelling or pain, which can indicate deep vein thrombosis and needs medical assessment.

Bone density and vitamin K2

Whole natto (not isolated nattokinase) is one of the richest food sources of vitamin K2 as menaquinone-7. Japanese observational studies, including one in postmenopausal women, have associated regular natto intake with lower rates of hip fracture. This is likely a vitamin K2 effect, not a nattokinase effect. Nattokinase capsules that do not contain K2 will not deliver this benefit.

Sinus and mucus

Nattokinase’s ability to break down mucoprotein has led to small trials in chronic rhinosinusitis. Results are early and mixed. It is not standard-of-care for sinus disease.

Real safety concerns

1. Bleeding risk with anticoagulants and antiplatelet drugs

This is the most important safety issue. Because nattokinase enhances fibrinolysis, combining it with a blood thinner amplifies bleeding risk. Do not take nattokinase if you are on:

• Warfarin (Coumadin)
• Direct oral anticoagulants (DOACs): apixaban (Eliquis), rivaroxaban (Xarelto), dabigatran (Pradaxa), edoxaban (Savaysa)
• Aspirin, including low-dose 81 mg
• Clopidogrel (Plavix), ticagrelor (Brilinta), prasugrel (Effient)
• Heparin or low-molecular-weight heparin (enoxaparin/Lovenox)

Case reports of intracranial and gastrointestinal bleeding in people combining nattokinase with anticoagulants exist in the medical literature. If your clinician has recommended these medications, do not add nattokinase without their explicit review.

2. Surgery, dental procedures, and injury

Stop nattokinase at least 2 weeks before any planned surgery or dental extraction. Tell your surgeon and anesthesiologist about all supplements. If you experience trauma or unusual bruising while on nattokinase, seek medical evaluation.

3. Bleeding disorders and low platelets

People with hemophilia, von Willebrand disease, immune thrombocytopenia, or a personal or family history of easy bleeding should not take nattokinase.

4. Low blood pressure and antihypertensive medications

Because nattokinase can lower blood pressure, adding it to an existing antihypertensive regimen can cause hypotension, presenting as dizziness, light-headedness, or fainting. If you are on ACE inhibitors, ARBs, calcium channel blockers, or diuretics, discuss the addition with your prescriber and monitor your home blood pressure.

5. Soy allergy

Natto is a soy product. Highly purified nattokinase supplements often claim to be soy-protein-free, but people with severe soy allergy should still be cautious and read labels carefully.

6. Pregnancy and breastfeeding

There is not enough safety data on nattokinase in pregnancy or breastfeeding. It should be avoided in both.

7. Children

There is no established pediatric dose. Nattokinase is not appropriate for children.

Who might reasonably consider a trial (with medical input)

• Adults with pre-hypertension or mild stage 1 hypertension who are pursuing lifestyle change and want a low-risk adjunct, with clinician awareness.
• Adults with a general cardiovascular-risk-reduction interest who are not on antiplatelet or anticoagulant therapy.
• People who tolerate natto poorly (its texture and smell are not for everyone) but want some of the enzyme’s effect.

Who should avoid nattokinase

• Anyone on warfarin, DOACs, aspirin, clopidogrel, or other antithrombotic drugs
• People with hemophilia, von Willebrand disease, low platelets, or any bleeding disorder
• People with peptic ulcer disease or active gastrointestinal bleeding
• Anyone within 2 weeks of a planned surgical or dental procedure
• Pregnant or breastfeeding women
• Children
• People with severe soy allergy without a hypoallergenic product verification
• People with symptomatic hypotension

How to use nattokinase more safely, if you and your clinician agree

• Start low. 100 mg (about 2,000 FU) once daily is a reasonable starting dose. Do not exceed 200 mg (4,000 FU) per day without specific guidance.
• Take with food to reduce any mild GI upset.
• Track your blood pressure at home. If you are on antihypertensives, check BP twice daily for the first 2 weeks and share numbers with your prescriber.
• Watch for bleeding signs. Unusual bruising, prolonged bleeding from small cuts, gum bleeding when brushing, nosebleeds, black or bloody stools, blood in urine, or an unexplained headache with weakness should trigger immediate medical attention.
• Choose a third-party-tested product. Look for USP, NSF, or an independent Certificate of Analysis to verify FU content matches the label.
• Do not stack with fish oil in high doses, garlic supplements, ginger extract, or ginkgo, which also have mild antiplatelet effects.
• Stop at least 2 weeks before any surgery or dental extraction.

Natto (the food) vs nattokinase (the supplement)

If you want the benefits attributed to natto, the whole food gets you the enzyme plus vitamin K2, plant protein, probiotic bacteria, and fiber, at a total nutritional value the isolated enzyme does not provide. If you tolerate the smell and texture, one serving (about 40 to 50 g, roughly a small takeaway pack) three to four times a week is a reasonable pattern shown in Japanese observational studies. Note that whole natto also contains vitamin K2, which affects warfarin dosing, so the anticoagulant precaution applies to the food as well.

Bottom line

Nattokinase is one of the better-studied supplements for modest cardiovascular support. The evidence supports small blood pressure reductions and probable improvements in fibrinolytic activity at 2,000 to 4,000 FU per day⁽¹⁾. It is not a treatment for diagnosed hypertension, coronary artery disease, deep vein thrombosis, or stroke prevention, and it should never be combined with anticoagulants or antiplatelet drugs without a prescriber’s approval. Used carefully, in the right person, it is a plausible low-risk adjunct. Used carelessly, especially with a blood thinner, it can cause serious bleeding.

Frequently asked questions

How much nattokinase should I take?

Most studies showing an effect used 2,000 to 4,000 fibrin units (FU) per day, which corresponds to about 100 to 200 mg. Start at the lower end and take with food. Do not exceed 200 mg per day without specific medical guidance.

Can I take nattokinase with aspirin or warfarin?

No, not without explicit approval from your prescriber. Nattokinase adds to bleeding risk on any anticoagulant or antiplatelet drug, including low-dose aspirin, warfarin, apixaban, rivaroxaban, dabigatran, clopidogrel, or heparin. Serious bleeding has been reported.

Does nattokinase lower blood pressure enough to replace medication?

No. Meta-analysis suggests reductions of about 3 to 5 mmHg, which is smaller than what a standard antihypertensive achieves. It is a possible adjunct in mild cases, not a substitute for prescribed therapy in diagnosed hypertension.

Is nattokinase safe long-term?

Short-to-medium term studies (up to a few months) show reasonable tolerability in the general adult population. Long-term safety data are limited. Periodic breaks and clinician review are sensible.

Can nattokinase dissolve existing blood clots?

It has clot-dissolving activity in laboratory assays and appears to enhance fibrinolysis in humans, but it is not an emergency treatment for a clot. Suspected stroke, heart attack, pulmonary embolism, or deep vein thrombosis needs immediate medical care, not a supplement.

Is nattokinase safe in pregnancy or for children?

No. There is not enough safety data in pregnancy or breastfeeding, and there is no established pediatric dose. Both groups should avoid it.

Should I stop nattokinase before surgery?

Yes. Stop at least 2 weeks before any planned surgery, dental extraction, or invasive procedure, and tell your surgeon and anesthesiologist about it.

Medical disclaimer: This article is for general information only and is not a substitute for professional medical advice, diagnosis, or treatment. Nattokinase enhances fibrinolysis and can cause serious bleeding when combined with anticoagulants (warfarin, apixaban, rivaroxaban, dabigatran, heparin) or antiplatelet drugs (aspirin, clopidogrel, ticagrelor). Do not take nattokinase if you have a bleeding disorder, active gastrointestinal bleeding, peptic ulcer disease, uncontrolled hypertension or hypotension, or if you are pregnant, breastfeeding, or a child. Stop nattokinase at least 2 weeks before any surgery or dental procedure. Do not use nattokinase to treat stroke, heart attack, deep vein thrombosis, or diagnosed hypertension in place of prescribed therapy.