Table of Contents
Table of Contents
Nattokinase is an enzyme found in the traditional Japanese food natto. Natto is made from boiled soybeans fermented with a bacterium known as Bacillus subtilis var. natto.
Nattokinase's history traces to 1980, when Dr. Hiroyuki Sumi, a Japanese researcher at the University of Chicago Medical School, was testing natural substances for their ability to dissolve blood clots. After screening more than 170 candidate foods, Sumi placed a sample of natto onto an artificial blood clot in a petri dish and watched it fully dissolve within 18 hours, faster than any pharmaceutical compound he had tested. He formally identified and named the enzyme "nattokinase" in a 1987 paper.1 While natto remains the only food source of the enzyme, research since then indicates that nattokinase supplements provide comparable effects without requiring daily consumption of fermented soybeans.
Nattokinase is primarily used to support cardiovascular health and the body's natural clot-breakdown processes. Because whole natto has a strong aroma and sticky texture, many people find it difficult to eat regularly, so supplements have become a more common delivery method.
Maintaining cardiovascular health is a primary wellness goal for adults. A significant factor in cardiovascular wellness is fibrinogen, a protein essential to healthy blood clotting but one that requires careful balance to support clear, healthy arteries. Healthy fibrinogen levels are associated with cardiovascular health, and elevated fibrinogen has consistently been identified as an independent risk marker for future cardiovascular disease in large prospective studies.2
Nattokinase supports heart health primarily by breaking down fibrinogen and excess fibrin in blood vessels. At the biochemical level, nattokinase works through multiple pathways: it directly breaks down cross-linked fibrin, converts the body's own prourokinase into active urokinase (which increases plasmin, the body's natural clot-dissolving enzyme), and inhibits plasminogen activator inhibitor-1 (PAI-1), a protein that would otherwise block this process. This multi-pathway action is why researchers describe nattokinase as supporting the body's own fibrinolytic system rather than acting as a single-mechanism blood thinner.3,4
In a randomized, controlled trial, 73 subjects looking to maintain cardiovascular wellness took either 2,000 FU of nattokinase or a placebo daily. After eight weeks, the nattokinase group showed healthy blood pressure within a normal range compared to the placebo. Researchers attributed this to improved blood vessel structure and function rather than a direct anti-hypertensive mechanism.5
Because nattokinase may help dissolve or prevent clots, supports vascular health, balanced fibrinogen levels, and support healthy cholesterol levels, it's frequently discussed in the context of cardiovascular health.3-6 That said, large-scale, long-term human trials specifically confirming improved cardiovascular wellness are still lacking. It should be treated as part of an overall healthy diet and exercise routine, not as a standalone preventive measure.
Beyond cardiovascular effects, nattokinase functions similarly to other proteolytic enzymes such as bromelain and serrapeptidase. By helping manage fibrin turnover, it may support healthy circulation to active muscles and tissues, helping deliver oxygen and nutrients while clearing metabolic byproducts. Human clinical trials testing nattokinase specifically for post-exercise recovery are still lacking, so this remains a mechanism-based benefit rather than a clinically confirmed one.
As a fermented food, natto is naturally rich in probiotics, and fermented foods broadly show antioxidant, antimicrobial, and anti-inflammatory activity.7 This benefit applies most directly to eating natto itself; an isolated nattokinase supplement does not carry the same probiotic content as the whole fermented food.
Ongoing sinus challenges are common in adults and can sometimes be difficult to manage. Researchers at Fukui University in Japan studied nattokinase's effect on nasal passage tissue, since excessive fibrin buildup can contribute to everyday sinus congestion.8
In the laboratory, researchers incubated nasal tissue from individuals experiencing sinus challenges with either saline or nattokinase at 37°C for 24 hours. They then separately incubated nasal discharge and mucus samples with nattokinase for one hour. The nattokinase-treated samples showed measurable fibrin breakdown and reduced mucus viscosity (thickness) compared to the saline control. Researchers noted that this mechanism might also provide support for broader, seasonal respiratory challenges, though this has not been directly tested in those specific populations. Current evidence is limited to these laboratory observations of nasal passage tissue and mucus.
Amyloid is a type of protein that can accumulate in tissue over time and is frequently associated with age-related cognitive decline. Laboratory studies show nattokinase can directly break down these amyloid structures in vitro.9-11
However, this is where the evidence trail stops for humans. A randomized trial of 120 adults seeking circulatory and cognitive support found that 4,000 FU of nattokinase twice daily for six months produced no significant improvement in cognitive function, memory, or attention compared to placebo.12
Nattokinase is one of several fibrinolytic enzymes used for circulatory support, and it's often compared to serrapeptidase and lumbrokinase.
Serrapeptidase, derived from bacteria in the silkworm gut, is generally used more for reducing tissue inflammation, sinus congestion, and post-surgical swelling than for dissolving existing blood clots.
Lumbrokinase, derived from earthworms, is frequently described by supplement manufacturers and some practitioners as substantially more potent than nattokinase. Figures like "30 times stronger" circulate widely. This claim should be read with caution: independent, standardized head-to-head clinical trials comparing the two enzymes are lacking, and most of these comparisons come from marketing material or practitioner anecdote rather than controlled research. For general, long-term cardiovascular support, nattokinase remains the most clinically documented option of the three.
No side effects have been reported in nattokinase clinical trials at typical doses, but the following are documented potential risks:
Beyond these general risks, published case reports describe serious outcomes at high or unmonitored doses: one report documented fatal internal bleeding in an elderly woman who was not taking other blood thinners, and another documented a brain hemorrhage in a woman taking 400 mg daily for one week. These cases underscore that nattokinase's blood-thinning effect is real and not risk-free, even without a drug interaction present.13-15
Nattokinase should not be combined with warfarin (Coumadin) or other prescription anticoagulants and antiplatelet drugs, including aspirin, clopidogrel, prasugrel, ticlopidine, and dipyridamole, except under a physician's direct supervision.
Herbal and Supplement Interactions. Beyond prescription medications, nattokinase should also be used cautiously alongside other natural compounds with blood-thinning properties, including ginkgo biloba, high-dose garlic, curcumin (turmeric), and high-dose fish oil/omega-3 supplements. Combining nattokinase with these can unpredictably compound the overall blood-thinning effect.
One distinction worth making clearly: this interaction risk applies to the isolated nattokinase enzyme. Whole natto carries a separate consideration; it is unusually high in vitamin K2, which can directly counteract warfarin's mechanism of action (warfarin works by blocking vitamin K). Someone on warfarin should be cautious about both the supplement (bleeding risk from the enzyme) and the whole food (reduced warfarin effectiveness from the vitamin K) for different reasons.
Most healthcare sources recommend discontinuing nattokinase at least two weeks before any scheduled surgery or invasive dental procedure, since its effects on clotting can persist for several days after the last dose.
There is not enough research to establish safety during pregnancy or breastfeeding; avoid unless a healthcare provider directs otherwise.
Always talk to your doctor before starting nattokinase if you take blood thinners or blood pressure medication, have a bleeding disorder, are pregnant or breastfeeding, or have an upcoming surgery.
One practical note: nattokinase potency should be judged in fibrinolytic units (FU), not milligrams; mg alone doesn't reflect enzyme activity. Check the label for an FU value.
Nattokinase is a protein-based enzyme sensitive to stomach acid, so it's commonly recommended to take it in a delayed-release or enteric-coated capsule on an empty stomach 30 to 60 minutes before a meal, or at least two hours after eating to reduce breakdown before absorption. Taking it with food may reduce how much active enzyme reaches the circulation. As a food, natto can be eaten on its own or added to rice, salads, wraps, or miso soup. As a supplement, it's most often taken as a capsule standardized to FU content.
Makes 12 cups
Ingredients:
Instructions:
Natto is rich in fiber, protein, manganese, iron, copper, magnesium, calcium, vitamin C, potassium, zinc, selenium, and B vitamins. It is also, by a wide margin, the richest dietary source of vitamin K2 in the MK-7 form.16 Regular natto provides roughly 775 mcg of MK-7 per 100g, far more than any other common food. MK-7 supports the activation of proteins involved in calcium regulation, helping direct calcium toward bone rather than arterial tissue. This is a distinct nutritional benefit from nattokinase's fibrinolytic activity, and it's the reason whole natto carries the separate warfarin caution noted above.
Yes, at the standard studied dose of 100 mg (2,000 FU) daily, nattokinase is safe. It should be used with caution under direct medical supervision in people on blood thinners or antiplatelet drugs.
Natto is a whole fermented soybean food; nattokinase is the enzyme within it. Natto also carries very high levels of vitamin K2, which a nattokinase supplement (isolated enzyme) does not.
Can I take nattokinase with aspirin? Not without medical supervision, both affect clotting, and combining them can increase bleeding risk.
Most sources recommend discontinuing at least two weeks before any scheduled surgery or invasive dental procedure.
FU (fibrinolytic units) measures actual enzyme activity. Milligram weight alone doesn't tell you potency.
Not based on current evidence, human trials over six months found no cognitive benefit despite promising lab-level data on amyloid breakdown.
Should I take nattokinase with food or on an empty stomach? For best results, nattokinase should be taken in a delayed-release (DR) or enteric-coated capsule on an empty stomach 30–60 minutes before eating, or two hours after.
Not recommended; safety during pregnancy or breastfeeding hasn't been established.
Is nattokinase stronger than serrapeptidase or lumbrokinase? Nattokinase has the most published human clinical data of the three. Lumbrokinase is often marketed as more potent, but that claim mostly comes from anecdotal and marketing sources rather than controlled head-to-head trials.
Use caution. Both have their own blood-thinning properties, and combining them with nattokinase can unpredictably increase overall bleeding risk.
Both carry risk, but for different reasons: the supplement's enzyme activity raises bleeding risk, while whole natto's high vitamin K content can reduce warfarin's effectiveness. Neither should be started without your doctor's involvement.
Nattokinase's best-supported benefits are cardiovascular, specifically, helping to maintain healthy blood pressure already within the normal range and supporting healthy circulation and blood flow. These are achieved through a multi-pathway effect on the body's own fibrinolytic system, with plausible but less-established effects on sinus health, a healthy inflammatory response, and metabolism. Brain-health claims are not yet backed by positive human trials. Compared to other fibrinolytic enzymes like serrapeptidase and lumbrokinase, nattokinase has the most published human clinical data for general cardiovascular support.
Because it influences circulatory pathways, anyone on blood thinners or blood pressure medication, anyone pregnant or breastfeeding, and anyone with upcoming surgery should talk to a healthcare provider before starting it.
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DISCLAIMER: These statements have not been approved by the Food and Drug Administration. These products are not intended to diagnose, treat, cure or prevent disease.
