Nattokinase is an enzyme used primarily to support cardiovascular health. It breaks down fibrin, the protein that forms the structural backbone of blood clots, and this clot-dissolving ability is the basis for nearly all of its uses. People take it as a supplement for blood clot prevention, blood pressure reduction, cholesterol management, and slowing the buildup of arterial plaque.
Where Nattokinase Comes From
Nattokinase is produced during the fermentation of soybeans by the bacterium Bacillus subtilis. The end product is natto, a traditional Japanese food with a sticky texture, strong smell, and an acquired taste. To make natto, whole soybeans are soaked overnight, steamed under pressure for 20 to 30 minutes, inoculated with the bacteria, and then cultured for about 24 hours. During that fermentation window, the bacteria produce nattokinase along with other bioactive compounds like vitamin K2 and soy isoflavones.
Most nattokinase supplements are extracted and purified from this fermentation process, then sold in capsule form. This lets people get the enzyme without eating natto itself.
How It Works in the Body
Nattokinase dissolves blood clots through several overlapping pathways. It directly breaks apart fibrin, the mesh-like protein that holds clots together. It also activates your body’s own clot-dissolving system by converting a dormant enzyme called prourokinase into its active form and by boosting levels of tissue plasminogen activator, another natural clot-buster. At the same time, it breaks down a substance called PAI-1 that normally slows clot dissolution. The net effect is that your blood’s ability to clear clots increases from multiple directions at once.
Even a single dose has been shown to trigger measurable clot breakdown. This potent fibrinolytic activity is stronger than plasmin, the body’s primary clot-dissolving enzyme, which is why nattokinase has attracted so much research attention as an oral alternative to conventional clot-prevention therapies.
Blood Clot Prevention
The most common reason people take nattokinase is to reduce the risk of dangerous blood clots. Clots that form inside blood vessels can block circulation to the heart, brain, or lungs, leading to heart attacks, strokes, or pulmonary embolism. Nattokinase’s combined antithrombotic and anticoagulant effects make it a candidate for people looking to lower that risk. Animal and human studies have confirmed that it enhances markers of both fibrinolysis (clot breakdown) and anticoagulation (clot prevention).
Atherosclerosis and Plaque Buildup
Beyond clot prevention, nattokinase appears to slow the progression of atherosclerosis, the gradual thickening and hardening of artery walls from plaque deposits. In a clinical study of 1,062 participants, daily supplementation at 10,800 fibrinolytic units (FU) for 12 months significantly reduced carotid plaque size and artery wall thickness compared to baseline measurements. A separate 26-week trial found similar reductions in plaque size and intima-media thickness, a standard measure of artery wall health.
Researchers believe this anti-atherosclerotic effect comes from the combined impact of nattokinase’s clot-dissolving, antioxidant, and lipid-lowering properties rather than any single mechanism. By reducing clot formation, it slows plaque progression. By lowering lipids, it reduces the raw material that builds plaque in the first place.
Blood Pressure Reduction
A randomized controlled trial found that eight weeks of nattokinase supplementation lowered systolic blood pressure by about 5.5 mmHg and diastolic blood pressure by about 2.8 mmHg compared to a control group. Those are modest but meaningful reductions, roughly comparable to what you might see from dietary changes like reducing sodium intake. For someone with borderline or mildly elevated blood pressure, that shift could be enough to move readings into a healthier range.
Cholesterol and Lipid Levels
Nattokinase has lipid-lowering effects, though the dose matters considerably. The 1,062-participant study found that 10,800 FU per day significantly improved lipid profiles over 12 months. However, 3,600 FU per day was ineffective for both lipid management and atherosclerosis progression. This is a key distinction because many commercial supplements are dosed well below the levels that showed benefits in clinical research.
Dosage: What the Research Actually Used
Nattokinase is measured in fibrinolytic units (FU), which reflect its clot-dissolving potency. The recommended dose in Europe is 2,000 FU per day, and many supplements fall in that range. Clinical trials, however, have used doses ranging from 1,200 FU to 13,000 FU daily, with wide variation in results.
The largest clinical study to date concluded that the effective dose for managing atherosclerosis and high cholesterol falls between 6,000 and 12,000 FU daily, far higher than what most supplements provide. At 3,600 FU per day, the researchers found no benefit for lipid levels or plaque progression. For blood pressure, positive results have been seen at lower doses in the 2,000 FU range, suggesting that different health goals may require different amounts.
This gap between what’s commonly sold and what clinical research supports is worth noting. If you’re taking nattokinase for general cardiovascular support, a standard 2,000 FU dose may offer some blood pressure benefit. If your goal is cholesterol or plaque management, the evidence points to substantially higher doses.
Safety and Drug Interactions
Because nattokinase is a potent clot-dissolving enzyme, the primary safety concern is bleeding. It has antiplatelet and anticoagulant properties, meaning it makes blood less likely to clot. For most people, this is the intended benefit. But for anyone already taking blood-thinning medications like warfarin or aspirin, stacking nattokinase on top creates a real risk of excessive bleeding. The same applies before surgery or dental procedures, where normal clotting is essential.
People with bleeding disorders or a history of hemorrhagic stroke should avoid nattokinase entirely. It is sold as a dietary supplement, not a regulated medication, so quality and potency can vary between brands. Nattokinase derived from natto also naturally contains vitamin K2, which can interfere with warfarin in the opposite direction, creating unpredictable effects on clotting. Many purified supplements remove vitamin K2, but labeling isn’t always clear.
Neuroprotective Effects
Early research suggests nattokinase may have neuroprotective properties, potentially by improving blood flow to the brain and reducing inflammation. This is one of its less-studied applications, and the evidence is not yet strong enough to recommend it specifically for brain health. Still, its ability to reduce clot formation and improve circulation could theoretically lower the risk of ischemic stroke, where a clot blocks blood supply to the brain.