What does nattokinase do to the brain?

Search "nattokinase" and "brain" together, and you'll find confident promises the research doesn't actually support.

Nattokinase is a clot-dissolving enzyme from fermented soybeans, and any effect it has on your brain works through your blood vessels, not directly on your brain cells—a distinction that matters, because high blood pressure, present in 48.1% of U.S. adults, is a leading driver of the vessel damage and clots that threaten the brain. This guide walks through what the strongest studies found, including one 3-year trial in 265 people, and where the evidence runs out.

Table of Contents

• 1. The Short Answer: Blood, Not Brain Cells
• 2. How a Clot-Dissolving Enzyme Reaches the Brain
• 3. Blood Pressure: Real, but Modest
• 4. Arteries, Plaque, and the Trial That Found Nothing
• 5. The Alzheimer's Question: Promising, but Only in the Lab
• 6. The Real Brain Risk to Know: Bleeding
• 7. Getting the Studied Dose Right
• Frequently Asked Questions
• Conclusion

1. The Short Answer: Blood, Not Brain Cells

Nattokinase doesn't act on your brain the way a stimulant or a neurotransmitter might—it's a fibrinolytic enzyme, which simply means it dissolves fibrin, the protein mesh that holds blood clots together. Isolated from the traditional Japanese food natto, it breaks down fibrin directly, blocks a clotting-brake protein called PAI-1, and boosts plasmin, your body's own clot-clearing enzyme.

Everything nattokinase might do "for the brain," then, is downstream of what it does in the bloodstream. There is no credible human evidence that it enters the brain and improves thinking, memory, or mood; if it helps the brain at all, it does so the way managing blood pressure does—by protecting the blood supply. That matters because high blood pressure is one of the leading causes of stroke, and one in three U.S. adults has at least one major stroke risk factor. This clot-clearing action is the mechanism behind how nattokinase works throughout the body.

2. How a Clot-Dissolving Enzyme Reaches the Brain

The brain depends on a constant, uninterrupted blood supply, and the most common strokes happen when a clot blocks an artery feeding it, starving brain tissue of oxygen. Because high blood pressure quietly damages arteries and encourages clots, it was a primary or contributing cause of 680,179 U.S. deaths in 2024—so an enzyme that helps clear clots and keep blood moving is, in theory, working on exactly the right target. Experimental studies also suggest nattokinase can reduce platelet clumping and modestly improve blood flow, the kind of effect that could, in principle, help keep circulation to brain tissue steady.

A plausible mechanism is a starting point, not proof. Plenty of compounds look promising in a test tube and do nothing measurable in a living person, which is why the human trials matter more than the biochemistry. Supplement strength is measured in fibrinolytic units (FU), and the studies most relevant to everyday use tested 2,000 FU a day—the amount in a single daily capsule—so those are the trials worth weighing most heavily.

3. Blood Pressure: Real, but Modest

Because blood pressure is the single biggest modifiable stroke risk, it's the most brain-relevant outcome nattokinase has been tested against—and here the evidence is genuinely encouraging, with caveats. In a randomized, placebo-controlled trial of 86 adults with pre-high or stage-1 high blood pressure, 2,000 FU daily for 8 weeks lowered systolic pressure by 5.55 mmHg and diastolic by 2.84 mmHg more than placebo.

A 2023 meta-analysis pooling 6 trials and 546 people found similar average reductions—about 3.45 mmHg systolic and 2.32 mmHg diastolic. Those numbers are meaningful across a whole population but modest for any one person, and the same analysis flagged a small rise in blood sugar—a reminder that "natural" doesn't mean "only upsides." The blood-pressure evidence is covered in more depth in our guide to nattokinase and blood pressure.

4. Arteries, Plaque, and the Trial That Found Nothing

Beyond blood pressure, the headline-grabbing claim is that nattokinase shrinks arterial plaque—including in the carotid arteries that feed the brain. A 2022 study of 1,062 people taking 10,800 FU a day for 12 months reported reduced carotid artery-wall thickness and plaque, with improvement rates of 66.5% to 95.4%; an earlier trial found plaque shrinking by roughly a third, outperforming a statin.

Read the fine print, though. Both used far more than a standard capsule—6,500 to 10,800 FU, three to five times a typical daily dose—and neither compared nattokinase against a placebo, so natural variation and other treatments can't be ruled out as the real cause.

Then comes the study that should temper the enthusiasm. The Nattokinase Atherothrombotic Prevention Study (NAPS)—the largest and most rigorous trial to date, randomizing 265 adults to 2,000 FU or placebo for a median 3 years—found no difference in carotid artery-wall thickness, arterial stiffness, or blood pressure. It used the same 2,000 FU dose found in everyday supplements, and it was even designed to track cognition. That doesn't make nattokinase useless—NAPS enrolled healthy, low-risk adults, so a benefit in higher-risk patients can't be ruled out—but it does mean the strongest evidence available shows no measurable effect in exactly the kind of person most likely to take it for prevention.

In short, the plaque evidence carries three asterisks:

• Doses of 6,500–10,800 FU, well above the 2,000 FU in a daily capsule
• No placebo group in the positive plaque trials, so cause and effect isn't established
• A rigorous 3-year, placebo-controlled trial (NAPS) found no benefit at 2,000 FU

5. The Alzheimer's Question: Promising, but Only in the Lab

You may have seen nattokinase linked to Alzheimer's disease. That idea traces to a 2009 laboratory study showing nattokinase can break down amyloid fibrils—the sticky protein clumps found in Alzheimer's—at normal body temperature and pH, an ability shared by only a handful of enzymes.

More recent work extended this to animals: a 2023 study reported nattokinase degrading amyloid-beta and lowering it in the blood of Alzheimer's-model mice. It's genuinely interesting biology—but it is test-tube and mouse data. The proposed idea also faces a practical hurdle: an enzyme swallowed as a capsule has to survive digestion and reach the bloodstream intact, and much of it does not. No human trial has shown nattokinase improves memory, slows cognitive decline, or prevents dementia, so treating it as a brain-protective supplement gets well ahead of the evidence.

6. The Real Brain Risk to Know: Bleeding

Here is the effect on the brain that is actually documented in people—and it's a caution, not a benefit. Because nattokinase reduces clotting, combining it with blood-thinning drugs can raise bleeding risk, including inside the skull. A published case report described a patient on aspirin who developed a cerebellar hemorrhage after just 7 days of nattokinase, with multiple small brain bleeds visible on MRI.

Major medical centers flag the same concern. Memorial Sloan Kettering notes that nattokinase may increase intracerebral hemorrhage risk with aspirin and bleeding risk with anticoagulant, antiplatelet, or clot-dissolving drugs, and documents serious harms—including a fatal internal bleed in one case and a dangerous clot on a mechanical heart valve when a patient swapped warfarin for nattokinase. This is why anyone considering it should read up on nattokinase and stroke prevention carefully and involve a clinician; we review that evidence in Nattokinase and Stroke Prevention.

Talk to your doctor before taking nattokinase if any of these apply:

• You take warfarin, a DOAC, aspirin, or another antiplatelet medication
• You have a bleeding disorder, recent surgery, or a history of brain bleeds
• You are pregnant or nursing, where safety data is lacking

7. Getting the Studied Dose Right

If you and your doctor decide nattokinase makes sense for your cardiovascular health, two things separate a product worth taking from one that isn't: the dose, and how well the enzyme survives digestion. The human trials most relevant to everyday use—including the blood-pressure studies and the 3-year NAPS trial—used 2,000 FU a day, so a supplement that delivers that amount reliably is doing the sensible thing.

BioAbsorb's Nattokinase Enzyme provides 100 mg (2,000 FU of activity) per capsule—matching that studied dose—in a DRcaps delayed-release veggie capsule that shields the enzyme from stomach acid, which matters because fibrinolytic enzymes are easily broken down before they can be absorbed. It leaves out vitamin K2, so longer-term or higher dosing doesn't raise K2-accumulation questions, and it's free of gluten, dairy, nuts, eggs, fish, shellfish, and animal products, making it fully vegetarian.

Every batch is third-party tested for potency (at least 2,000 FU per capsule), heavy metals, and microbial contaminants—the kind of transparency worth expecting from any supplement. A single bottle contains 60 capsules—a 60-day supply at one capsule daily, taken on an empty stomach. You can review the full specifications and testing on the product page, or read more about BioAbsorb's Canadian GMP manufacturing.

Frequently Asked Questions

Does nattokinase improve memory or brain function?

There is no human evidence that it does. The interest comes from laboratory research showing nattokinase can break down amyloid proteins, but that work is limited to test tubes and mice—no trial has shown improved memory or cognition in people.

Can nattokinase prevent a stroke?

No study has tested that directly. The idea is plausible because nattokinase dissolves clots and clots cause most strokes, but the largest trial, NAPS, found no effect on the artery and blood-pressure markers that predict stroke risk. Anyone focused on stroke prevention should prioritize proven steps like blood-pressure control.

Is nattokinase worth taking for the brain if I'm already healthy?

The evidence doesn't support it. NAPS specifically studied healthy adults without heart disease and found no benefit over a median 3 years, so healthy people are unlikely to gain brain protection from it.

Can I take nattokinase with aspirin or blood thinners?

Not without medical guidance. Nattokinase can add to the effect of blood-thinning drugs and may raise the risk of bleeding, including in the brain. If you take any anticoagulant or antiplatelet medication, talk to your doctor before starting.

What dose did the brain-relevant studies use?

It varies by outcome. The blood-pressure trials used 2,000 FU a day, while the plaque studies used much higher doses of 6,500 to 10,800 FU—three to five times a typical capsule—which is part of why those plaque results are hard to apply to everyday use.

Is getting nattokinase from natto food better than a supplement?

Natto does contain nattokinase, but the amount varies batch to batch, making it hard to match the 2,000 FU dose used in trials. Supplements are standardized to a set fibrinolytic-unit count, which is why studies use them—though whole natto also provides fiber, vitamin K2, and probiotics that isolated capsules don't.

Conclusion

So, what does nattokinase do to the brain? On the evidence, its only plausible route is indirect—supporting healthy blood flow and blood pressure—and even that is modest, with the most rigorous 3-year trial finding no measurable effect at the standard 2,000 FU dose. The one clearly documented brain effect in people is a bleeding risk when it's combined with blood thinners, which is why—for anyone taking those medications or managing a heart condition—a conversation with your doctor is the essential first step rather than an afterthought. If you and your clinician decide it fits your cardiovascular plan, you can review the dose and third-party testing behind BioAbsorb's Nattokinase Enzyme.

Research References

1. Nattokinase Atherothrombotic Prevention Study (NAPS): A Randomized Controlled Trial. Clinical Hemorheology and Microcirculation, Vol. 78, No. 4 (2021), pp. 339–353. A 3-year, placebo-controlled trial in 265 adults found nattokinase (2,000 FU/day) had no effect on carotid artery-wall thickness, arterial stiffness, or blood pressure.
2. Effects of Nattokinase on Blood Pressure: A Randomized, Controlled Trial. Hypertension Research, Vol. 31, No. 8 (2008), pp. 1583–1588. In 86 adults with elevated blood pressure, 2,000 FU/day for 8 weeks reduced systolic pressure by 5.55 mmHg and diastolic by 2.84 mmHg versus placebo.
3. Effective Management of Atherosclerosis Progress and Hyperlipidemia with Nattokinase: A Clinical Study with 1,062 Participants. Frontiers in Cardiovascular Medicine, Vol. 9 (2022), article 964977. High-dose nattokinase (10,800 FU/day) for 12 months was associated with reduced carotid plaque and artery-wall thickness; a 3,600 FU/day dose was not.
4. Amyloid-Degrading Ability of Nattokinase from Bacillus subtilis Natto. Journal of Agricultural and Food Chemistry, Vol. 57, No. 2 (2009), pp. 503–508. Laboratory study showing nattokinase can degrade amyloid fibrils at normal body temperature and pH.
5. Degradation of Amyloid β-Peptides Catalyzed by Nattokinase In Vivo and In Vitro. Food Science and Human Wellness, Vol. 12, No. 5 (2023), pp. 1905–1916. Reported that nattokinase degraded amyloid-beta in laboratory assays and reduced it in the blood of Alzheimer's-model mice.
6. Cerebellar Hemorrhage Provoked by Combined Use of Nattokinase and Aspirin in a Patient with Cerebral Microbleeds. Internal Medicine, Vol. 47, No. 5 (2008), pp. 467–469. Case report of a brain hemorrhage after 7 days of nattokinase in a patient already taking aspirin.
7. Nattokinase Supplementation and Cardiovascular Risk Factors: A Systematic Review and Meta-Analysis of Randomized Controlled Trials. Reviews in Cardiovascular Medicine, Vol. 24, No. 8 (2023), article 234. Pooled 6 trials (546 participants), finding average reductions of about 3.45 mmHg systolic and 2.32 mmHg diastolic blood pressure.
8. Nattokinase: A Promising Alternative in Prevention and Treatment of Cardiovascular Diseases. Biomarker Insights, Vol. 13 (2018). Review describing nattokinase's fibrinolytic mechanism and summarizing clinical findings, including higher-dose carotid-plaque data.
9. Stroke Facts. Centers for Disease Control and Prevention (2025). Notes that high blood pressure, high cholesterol, smoking, obesity, and diabetes are leading causes of stroke, and that one in three U.S. adults has at least one risk factor.
10. High Blood Pressure Facts. Centers for Disease Control and Prevention (2026). Reports that about 48.1% of U.S. adults have high blood pressure, a primary or contributing cause of 680,179 deaths in 2024.
11. Nattokinase. Memorial Sloan Kettering Cancer Center, Integrative Medicine. Summarizes nattokinase's uses, drug interactions, and documented adverse events, including increased intracerebral hemorrhage risk with aspirin.

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.