Nattokinase has 10 clinical trials behind it, which is a great deal more than most supplements manage. It also has 7 published case reports, and 1 of those describes a death.
Both of those statements are true at the same time, and almost no page tells you both.
Quick Answer: What Is Nattokinase?
Nattokinase is a fibrinolytic enzyme produced when Bacillus subtilis ferments soybeans into natto. PubMed holds 331 records on it, of which 102 are tagged human, 10 are clinical trials and 2 are meta-analyses. A 2024 meta-analysis found no major adverse events across the trials. Separately, 7 case reports describe harms, including a fatal bleed. Both are real, and the difference is who was taking it.
Key Takeaways
- Nattokinase is 1 enzyme, made when bacteria ferment soybeans into natto.
- PubMed holds 331 records, 10 clinical trials and 2 meta-analyses.
- The same literature also contains 7 case reports of harm.
- 2000 FU is the dose the trials used, and our label carries it.
- It must never be combined with 1 of the prescription blood thinners.
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What It Actually Is
Nattokinase is not a herb and not a plant extract. It is an enzyme, and where it comes from explains most of what follows.
- Source: Bacillus subtilis fermenting boiled soybeans.
- The food: Natto, a traditional Japanese breakfast dish.
- What it does: Breaks down fibrin, the protein that forms clots.
- Measured in: Fibrin units, written FU, not milligrams.
- Our capsule: 2000 FU, which is 100 mg of the enzyme.
Because it acts on clotting, everything about it turns on what else you take, which is set out in what you must not combine it with.
The Numbers Behind It
Most supplement pages describe this evidence base with an adjective. It is more useful as a count.
| What PubMed holds on nattokinase | Count |
|---|---|
| Records mentioning nattokinase | 331 |
| Records tagged as human | 102 |
| Randomized or clinical trials | 10 |
| Systematic reviews or meta-analyses | 2 |
| Case reports | 7 |
Ten trials and 2 meta-analyses is a genuinely respectable file for a supplement. Seven case reports in the same file is unusual, and it is the part that gets left out.
What the Trials Measured
The trials are real and they measured real things, mostly markers in blood rather than events in people.
| Study | Who | What it measured |
|---|---|---|
| Single-dose crossover, 2016 | 12 healthy men, 2000 FU | Clotting and fibrinolysis markers |
| Open-label trial, 2009 | Healthy and at-risk adults | Fibrinogen, factor VII, factor VIII |
| Randomized trial, 2019 | 50 plus 50, high cholesterol | Prothrombin and closure times |
| Atherothrombotic prevention, 2021 | 265 adults, median age 65.3 | Subclinical atherosclerosis |
The single-dose crossover used 2000 FU and is where our label number comes from.[1]A single-dose of oral nattokinase potentiates thrombolysis and anti-coagulation profiles — Scientific Reports (2016) View source The 2009 trial reported falls in fibrinogen and in factors VII and VIII, though it was open-label and self-controlled rather than randomized.[2]Nattokinase decreases plasma levels of fibrinogen, factor VII, and factor VIII in human subjects — Nutrition Research (2009) View source
The largest is the 2021 atherothrombotic prevention study, which enrolled 265 people of median age 65.3 and noted that no large-scale long-term cardiovascular study had been done before it.[3]Nattokinase atherothrombotic prevention study: A randomized controlled trial — Clinical Hemorheology and Microcirculation (2021) View source How much of that translates into a dose is in what a fibrin unit means.
Blood Pressure and Cholesterol
These are the 2 outcomes the marketing leans on hardest, and the meta-analysis is the place to look rather than any single study.
- What was pooled: Randomized trials across 4 databases.
- What the authors say: Existing clinical evidence is various.
- Safety finding: No major adverse events in the included trials.
- What that does not cover: The 7 case reports, which are not trials.
A 2024 systematic review and meta-analysis is the current best summary of the benefit side.[4]Nattokinase Supplementation and Cardiovascular Risk Factors: A Systematic Review and Meta-Analysis of Randomized Controlled Trials — Reviews in Cardiovascular Medicine (2024) View source Read as a summary of trials it is fair. Read as a summary of everything published, it is incomplete.
The Case Reports Exist Too
Seven case reports sit in the same database as the 10 trials, and 4 of them matter to anyone deciding whether to take this.
| Case report | What happened | Year |
|---|---|---|
| Hemoperitoneum, elderly woman | Bleeding into the abdomen, and the patient died | 2022 |
| Warfarin substitution | Swapped warfarin for nattokinase after a mechanical valve | 2015 |
| Cerebellar haemorrhage | On aspirin, after 7 days of nattokinase, with microbleeds | 2008 |
| Anaphylaxis | In a patient with an existing fermented soybean allergy | 2022 |
A case report proves something happened once. It does not tell you how often, and it should not be read as a rate. The full picture is in side effects and dangers.
What Is Actually in Our Bottle
We would rather state this plainly than let the front label do the talking, because our product is not a plain nattokinase.
- Nattokinase: 2000 FU, which is 100 mg.
- Also included: A 1000 mg proprietary garlic and turmeric blend.
- What that means: The enzyme dose matches the trials, the blend does not.
- Per bottle: 60 vegan capsules, which is 2 months at 1 daily.
On those terms a 2000 FU capsule gives you the studied enzyme amount alongside 2 culinary herbs we have not tested separately.
Do Not Start Nattokinase, and Speak to a Clinician First, If
- You take warfarin, a DOAC, aspirin, clopidogrel or any other anticoagulant or antiplatelet
- You have a mechanical heart valve, a stent or any implanted cardiac device
- You have a bleeding disorder such as haemophilia, or a history of haemorrhagic stroke
- You have surgery or a dental procedure booked within the next 2 weeks
- You are pregnant, breastfeeding, or allergic to soy or natto
Frequently Asked Questions
What are the pros and cons of taking nattokinase? +
The pro is 10 clinical trials and 2 meta-analyses, which is more than most supplements have. The con is 7 case reports, including a fatal bleed.
What is nattokinase good for? +
Trials have measured clotting markers, blood pressure and cholesterol. 0 trials have measured whether it prevents a heart attack or a stroke.
Why don't doctors recommend nattokinase? +
Mostly because it affects clotting and 1 published case describes a patient replacing warfarin with it after a valve replacement.
Is nattokinase a blood thinner? +
It is fibrinolytic, meaning it breaks fibrin down. That is not the same mechanism as the 2 main classes of prescription blood thinner.
How much nattokinase is in your capsule? +
2000 FU, which is 100 mg of enzyme, plus a 1000 mg proprietary garlic and turmeric blend. There are 60 capsules per bottle.
Does nattokinase lower blood pressure? +
The 2024 meta-analysis pooled randomized trials on exactly this. The authors describe the existing clinical evidence as various rather than settled.
Is it okay to take nattokinase every day? +
The 2021 trial ran long term in 265 adults without major adverse events. Daily use is still a decision to make with whoever manages your medication.
What does FU mean on the label? +
Fibrin units, a measure of enzyme activity rather than weight. 2000 FU is the amount used in the single-dose crossover trial.
Is nattokinase the same as eating natto? +
No. Natto also carries vitamin K2, which acts in the opposite direction on clotting, and 1 serving is not standardised in FU.
Can nattokinase dissolve an existing clot? +
That has never been shown in any of the 10 trials and we do not claim it. A suspected clot is an emergency, not a supplement decision.
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