Nattokinase is an enzyme from fermented soybeans that may help thin blood and support circulation
Nattokinase is a protein-digesting enzyme extracted from natto, a traditional Japanese food made by fermenting soybeans with a specific bacterium. The enzyme breaks down fibrin, a protein involved in blood clotting, which is why it's studied for its potential to support circulation and reduce clot formation. Unlike prescription blood thinners, nattokinase works through a different mechanism — it doesn't prevent clotting entirely but may help your body clear excess fibrin more efficiently.
The compound gained attention in longevity research because cardiovascular disease and clot-related events are leading causes of age-related decline. Some researchers theorize that maintaining healthy fibrin levels could reduce the risk of heart attack and stroke. However, the evidence in humans remains limited, and most studies have been small or conducted in Japan where natto consumption is common.
Key Takeaways
- Nattokinase is derived from fermented soybeans and works by breaking down fibrin, a protein involved in blood clotting.
- Most human research on nattokinase comes from small studies or observational data, not large randomized trials.
- Nattokinase can interact with blood thinners like warfarin and aspirin, so medical supervision is necessary if you take either.
- Typical doses range from 100 to 200 fibrinolytic units (FU) per day, taken on an empty stomach for better absorption.
- You can obtain nattokinase through natto itself, though supplement forms offer a standardized dose without the acquired taste.
How nattokinase affects blood clotting and fibrin
When you have an injury, your body forms blood clots to stop bleeding — fibrin is the protein that creates the mesh holding the clot together. Normally, your body breaks down fibrin once the wound heals, but fibrin can accumulate in blood vessels over time, potentially narrowing them or contributing to clot formation. Nattokinase appears to speed up the breakdown of excess fibrin without preventing normal clotting when you actually need it.
In test-tube and animal studies, nattokinase has shown the ability to dissolve fibrin directly. A few small human studies have measured fibrin levels before and after nattokinase supplementation and found reductions, but these studies involved fewer than 100 people and were often conducted in Japan. The enzyme also appears to have mild antiplatelet effects, meaning it may slightly reduce platelet stickiness — another factor in clot formation.
The practical significance of these findings remains unclear. A reduction in fibrin levels in a blood test does not automatically translate to a lower risk of heart attack or stroke in real life. Larger, longer studies in diverse populations would be needed to establish whether nattokinase actually prevents cardiovascular events.
What the research shows about cardiovascular outcomes
Most nattokinase research has focused on blood markers rather than actual health outcomes. Studies have measured fibrin levels, blood viscosity, and platelet function, but few have tracked whether people taking nattokinase actually experience fewer heart attacks, strokes, or clots. The largest human study involved about 100 participants and found modest improvements in blood flow markers after 8 weeks, but this is not the same as proving the supplement prevents disease.
One observational study in Japan compared natto eaters to non-eaters and found lower rates of cardiovascular death in the natto group, but observational data cannot prove cause and effect — people who eat natto regularly may differ in many other ways. A small randomized trial in people with high cholesterol found that nattokinase reduced fibrin levels but did not significantly change cholesterol or blood pressure.
The gap between "nattokinase breaks down fibrin in a test tube" and "nattokinase prevents heart attacks in people" is substantial. Until larger, long-term trials are completed, nattokinase remains in the category of compounds with plausible mechanisms but unproven clinical benefit.
Dosing, timing, and how to take nattokinase
Nattokinase supplements are typically standardized to fibrinolytic units (FU), a measure of enzyme activity. Most commercial supplements contain 100 to 200 FU per capsule, and the typical dose used in research is 100 to 200 FU once or twice daily. Some products are labeled in milligrams instead; a rough conversion is that 2,000 milligrams equals about 100 FU, though this varies by manufacturer.
Absorption is better on an empty stomach, so taking nattokinase 30 minutes to 2 hours before a meal or 2 hours after eating is standard practice. If you experience stomach upset, taking it with a small amount of food is acceptable, though it may reduce absorption slightly. Consistency matters — most studies gave nattokinase daily for at least 4 to 8 weeks before measuring changes in blood markers.
Nattokinase is heat-sensitive, so the enzyme loses activity if exposed to high temperatures during manufacturing or storage. Check the label for a manufacturing date and store supplements in a cool, dry place. Reputable brands will include third-party testing to verify the FU content matches the label.
Drug interactions and who should avoid nattokinase
The most important concern with nattokinase is its interaction with blood-thinning medications. If you take warfarin (Coumadin), apixaban (Eliquat), dabigatran (Pradaxa), or other anticoagulants, adding nattokinase could increase bleeding risk. The same applies to antiplatelet drugs like aspirin, clopidogrel (Plavix), and ticagrelor (Brilinta). Even though nattokinase works differently than these drugs, the combined effect on clotting could be unpredictable.
People with bleeding disorders, a history of hemorrhagic stroke, or those scheduled for surgery should not take nattokinase without explicit approval from their doctor. Pregnant and breastfeeding women should avoid it because safety data in these populations does not exist. If you have a family history of bleeding disorders or are unsure whether nattokinase is safe for you, discuss it with your healthcare provider before starting.
Nattokinase may also interact with NSAIDs like ibuprofen and naproxen, which have their own antiplatelet effects. Combining multiple blood-thinning substances increases the risk of unexpected bleeding, including nosebleeds, bruising, or gastrointestinal bleeding.
Nattokinase from food versus supplements
Natto itself — the fermented soybean dish — contains nattokinase naturally, along with other compounds like vitamin K2 and probiotics. A typical serving of natto (about 50 grams) contains roughly 100 to 200 FU of nattokinase, equivalent to a standard supplement dose. If you enjoy the taste and texture, eating natto regularly is a way to consume nattokinase without buying supplements.
The drawback is that natto has a strong, pungent smell and a slimy texture that many people outside Japan find unpalatable. It's also not widely available in regular grocery stores in North America or Europe, making it impractical for most readers. Supplements offer a standardized dose, no acquired taste, and easier tracking of how much you're taking — useful if you're monitoring your intake alongside other supplements or medications.
One consideration: natto also contains high levels of vitamin K2, which can interfere with warfarin. If you're on warfarin, eating natto is not recommended because the vitamin K2 content will reduce the drug's effectiveness. Nattokinase supplements without added vitamin K2 avoid this problem, though you should still check with your doctor.
Cost, quality, and where to find nattokinase
Nattokinase supplements are available from most online retailers, health food stores, and some conventional pharmacies. Prices typically range from $10 to $30 per month depending on the dose and brand. Because nattokinase is not regulated as strictly as prescription drugs, quality varies — some products contain less enzyme activity than the label claims, while others may be contaminated or degraded.
Look for brands that include third-party testing from organizations like NSF International, USP, or ConsumerLab. These certifications mean an independent lab has verified that the product contains what the label says and is free of contaminants. Avoid products with vague labeling, no manufacturing date, or prices that seem too low — these are red flags for poor quality.
If you're buying online, check the seller's return policy and whether they store supplements in temperature-controlled conditions. Nattokinase degrades in heat, so supplements shipped in summer or stored in warehouses without climate control may have lost potency by the time they reach you.
Frequently Asked Questions
Can nattokinase replace my blood thinner medication?
No. Nattokinase is not approved to treat or prevent any disease, and its effects on clotting are much weaker than prescription blood thinners. If you have a history of clots, heart attack, or stroke, your doctor prescribed a specific medication for a reason. Do not stop taking it in favor of nattokinase without medical guidance.
How long does it take to feel the effects of nattokinase?
Most research measured changes in blood markers after 4 to 8 weeks of daily use. You won't feel nattokinase working — there are no obvious symptoms of improved fibrin breakdown. If you're taking it, you're betting on long-term cardiovascular benefits that may or may not materialize, not on when ready effects you can notice.
Is nattokinase safe to take long-term?
Limited data exists on long-term safety. The longest human studies lasted a few months. In that timeframe, nattokinase appeared well-tolerated with minimal side effects beyond occasional mild stomach upset. However, decades-long safety data do not exist, so taking it indefinitely is an unknown risk.
What's the difference between nattokinase and serrapeptase?
Both are proteolytic enzymes that break down proteins, and both are marketed for circulation and fibrin reduction. Serrapeptase comes from silkworm cocoons, while nattokinase comes from fermented soybeans. Research on serrapeptase is even more limited than on nattokinase, and neither has strong evidence for preventing cardiovascular disease in humans.
Can I take nattokinase if I have high blood pressure?
Nattokinase is not a blood pressure medication and won't lower your numbers. If you have high blood pressure, your doctor may have prescribed specific drugs for that condition. Nattokinase might theoretically support circulation, but it should not replace prescribed treatment. Always discuss supplements with your doctor if you have a chronic condition.