Nattokinase is an enzyme from fermented soybeans. Its best evidence is a small blood pressure drop, about 3.45 mmHg systolic across 6 short trials with 546 people. The largest long-term trial, 265 adults over a median of 3 years, found no effect on artery thickening. It changes clotting tests, so people on aspirin or blood thinners should ask a doctor first.
On this page
- What is nattokinase?
- What are the main nattokinase benefits for blood pressure?
- Does nattokinase dissolve plaque?
- What does the research show, study by study?
- Does nattokinase thin your blood?
- What are the nattokinase dangers and side effects?
- Who should not take nattokinase?
- What nattokinase dosage was used in studies?
- Is a nattokinase supplement the same as eating natto?
- What do doctors use first for high blood pressure?
- Nattokinase label checklist
- Bottom line on nattokinase benefits
- FAQ
Nattokinase benefits are studied mostly for blood pressure and blood flow, and this guide covers what the research shows, the bleeding risk with blood thinners and the results of the large atherosclerosis trial. We read two blood pressure trials, a 2023 pooled analysis of six randomized trials, the three-year NAPS artery trial, two clotting studies, a bleeding case report, a 2026 cognition trial, the NIH vitamin K fact sheet and the NHLBI page on blood pressure treatment. How we choose and grade sources is explained on our how we review page.
The short answer: across six small trials with 546 people, nattokinase lowered systolic blood pressure by about 3.45 mmHg, but the longest trial, 265 adults followed for a median of 3 years, found no effect on artery thickening, and the enzyme can add to bleeding risk.[4][5][9]
| What it is | An enzyme made by the bacterium Bacillus subtilis when soybeans are fermented into natto.[1] |
|---|---|
| Studied for | Blood pressure, artery wall thickening and blood clotting markers.[4][5][7] |
| Amounts in trials | Most trials used 2,000 FU a day. One 2022 study used 10,800 FU a day.[2][6] |
| Best evidence | A small drop in blood pressure, pooled from 6 randomized trials.[4] |
| Biggest letdown | No slowing of atherosclerosis over a median of 3 years in the NAPS trial.[5] |
| Main safety point | It changes clotting test results and was linked to a brain bleed in a person taking aspirin.[8][9] |
| Who should check first | Anyone who takes aspirin, warfarin or another drug that slows clotting.[9][11] |
What is nattokinase?
Nattokinase is an enzyme that the bacterium Bacillus subtilis makes while it ferments soybeans into natto, a traditional Japanese food.[1] Researchers became interested in it because lab and animal work suggested it can break down fibrin, the protein mesh that holds a blood clot together.[1] That is why most human studies measure blood pressure, blood vessels and clotting markers.
Supplement labels usually give the dose in fibrinolytic units, or FU. This is a measure of enzyme activity, not weight. The 2008 Korean blood pressure trial used 2,000 FU a day.[2] A 2016 US trial listed its dose as 100 mg a day of an extract with the vitamin K2 taken out.[3]
So a label that lists only milligrams is hard to compare with the trials. Look for the FU number when you read the research or a product label.
What are the main nattokinase benefits for blood pressure?
The clearest nattokinase benefit in human trials is a small drop in blood pressure, about 3 to 6 mmHg systolic, in adults whose readings were already high.[2][4] These blood pressure trials were short.
In the 2008 trial, 86 adults with systolic pressure of 130 to 159 mmHg took 2,000 FU a day or a placebo for 8 weeks. Compared with placebo, systolic pressure fell 5.55 mmHg and diastolic pressure fell 2.84 mmHg. Of the 86, 73 finished the study.[2]
The 2016 trial enrolled 79 adults, and 74 completed it. Average diastolic pressure went from 87 to 84 mmHg in 8 weeks, while the placebo group stayed at 87. Men saw a larger change, from 86 to 81 mmHg.[3]
A 2023 meta-analysis pooled 6 randomized trials with 546 people. It found average drops of 3.45 mmHg systolic and 2.32 mmHg diastolic.[4] The same analysis saw a slight rise in blood glucose (mean difference 0.40) and higher total cholesterol, and it reported no notable adverse events.[4] These trials tracked readings and lab values. They did not measure heart attacks or strokes.
Does nattokinase dissolve plaque?
No well-run trial shows that nattokinase dissolves plaque in human arteries, and the longest placebo-controlled trial found no effect on artery thickening.[5] Anyone buying it for artery health should weigh this result first.
The Nattokinase Atherothrombotic Prevention Study, or NAPS, was published in 2021. It gave 265 adults with a median age of 65.3 either 2,000 FU a day or a placebo, for a median of 3 years.[5] The researchers reported a “null effect on subclinical atherosclerosis progression.” Blood pressure and every lab measure also stayed the same as placebo.[5]
A 2022 study from China with 1,062 participants reported thinner carotid artery walls (CIMT) and smaller plaques after 12 months at 10,800 FU a day. It also said 3,600 FU a day did not work.[6] Its abstract does not describe randomization or a placebo group, and one author is listed with a supplement company, Sungen Bioscience.[6] We count it as limited evidence.
When a three-year randomized trial and a less controlled study disagree, we give the randomized trial more weight, so we do not consider the plaque claim supported.
What does the research show, study by study?
Most nattokinase studies are small and short, and the only multi-year randomized trial was negative.[5] The table lists the human studies we read, with who took part, the dose and what happened.
| Study | Who and how long | Dose | Result |
|---|---|---|---|
| Kim, 2008[2] | 86 adults with high-normal or high blood pressure, 8 weeks | 2,000 FU a day | Systolic down 5.55 mmHg, diastolic down 2.84 mmHg versus placebo |
| Jensen, 2016[3] | 79 adults, 74 finished, 8 weeks | 100 mg a day, vitamin K2 removed | Diastolic 87 to 84 mmHg; placebo stayed at 87 |
| Li, 2023 meta-analysis[4] | 6 randomized trials, 546 people | Varied | Systolic down 3.45 mmHg, diastolic down 2.32 mmHg |
| NAPS, Hodis, 2021[5] | 265 adults, median 3 years | 2,000 FU a day | No effect on artery thickening, blood pressure or labs |
| Chen, 2022[6] | 1,062 people, 12 months, design not described | 10,800 FU a day | Reported thinner artery walls; 3,600 FU a day did not work |
| Kurosawa, 2015[7] | 12 healthy young men, one dose | 2,000 FU once | Clotting markers shifted but stayed in the normal range |
| Yoo, 2019[8] | 100 adults with high cholesterol, 8 weeks | Not stated in abstract | Longer C-EPI closure time and aPTT |
| ICC-PACS, Zhang, 2026[10] | 120 adults with narrowed head or neck arteries, 6 months | 8,000 FU a day | No gain in overall thinking skills |
The 2026 cognition trial deserves a note. It enrolled 120 adults with narrowed arteries in the head or neck who had no symptoms, and gave 8,000 FU a day for 6 months. Nattokinase “did not improve global cognition,” though the authors saw an exploratory signal in visuospatial skills.[10]
Does nattokinase thin your blood?
Nattokinase changes several clotting test results in people, which is why doctors treat it as something that may add to bleeding risk.[7][8] In healthy people the shifts were small and moved the same way blood thinners move these tests.
In a 2015 study, 12 healthy young men took a single 2,000 FU dose. D-dimer, a marker of clot breakdown, rose at 6 and 8 hours. The aPTT clotting time was longer at 2 and 4 hours. The authors noted that all of these changes stayed within the normal range.[7]
A 2019 trial gave nattokinase or a placebo to 100 adults whose total cholesterol was 200 to 280 mg/dL, 50 in each group, for 8 weeks. The nattokinase group had longer C-EPI closure time and aPTT.[8] Both are lab tests of how quickly blood forms a clot.
Lab changes like these do not prove a person will bleed. They are the reason doctors worry about adding nattokinase to a prescribed blood thinner.[8][9]
What are the nattokinase dangers and side effects?
The main known danger of nattokinase is bleeding, especially when it is combined with aspirin or another drug that slows clotting.[9] Other side effects in the trials were few, but the trials were small.
A 2008 case report described a patient taking aspirin who had an acute bleed in the cerebellum, the back part of the brain, after taking nattokinase 400 mg a day for 7 days in a row. Brain scans also showed small older bleeds called microbleeds.[9] One case cannot prove cause and effect. It does match the clotting test changes seen in trials.[8]
In the pooled trials, no notable adverse events were reported. The same 2023 analysis did see a small rise in blood glucose and higher total cholesterol.[4] Studies of a few hundred people over a few weeks can miss rare harms, so few reported problems still leaves open what happens over years.
Nattokinase pros and cons, in short: the pro is a modest blood pressure drop in short trials; the cons are no shown benefit for arteries over 3 years and a possible bleeding risk.[4][5][9]
Who should not take nattokinase?
People who take aspirin, warfarin or other drugs that slow clotting, or who have had bleeding in the brain, should not start nattokinase without a doctor’s clear approval.[9] The list below covers the groups with the clearest reasons to skip it or ask first.
- People on aspirin or other antiplatelet drugs. The reported brain bleed happened in a person taking aspirin.[9]
- People on warfarin or another anticoagulant. Nattokinase prolongs clotting times, and natto the food is very high in vitamin K, which interacts with warfarin.[8][11]
- People with a past brain bleed or known microbleeds.[9]
- People working to bring down blood sugar or cholesterol, since pooled trials saw small rises in both.[4]
- People who are pregnant or breastfeeding. We did not find any trials in these groups, so there is no safety data to rely on.
- Anyone with high blood pressure who would use it in place of prescribed medicine.[12]
What nattokinase dosage was used in studies?
There is no established nattokinase dosage; human studies have used between 2,000 and 10,800 FU a day.[2][6] The table matches each dose to the study that used it and what was found. Use it to read the research. It does not tell you what to take.
| Dose | Length | What was found |
|---|---|---|
| 2,000 FU, one dose[7] | Single day | Clotting markers changed, all within the normal range |
| 2,000 FU a day[2] | 8 weeks | Blood pressure fell versus placebo |
| 2,000 FU a day[5] | Median 3 years | No effect on artery thickening |
| 3,600 FU a day[6] | 12 months | Reported as not effective in that study |
| 8,000 FU a day[10] | 6 months | No gain in overall thinking skills |
| 10,800 FU a day[6] | 12 months | Reported thinner artery walls; limited study design |
| 100 mg a day, K2 removed[3] | 8 weeks | Small diastolic drop |
| 400 mg a day with aspirin[9] | 7 days | Case report of a brain bleed |
Only the non-randomized 2022 study suggests a higher dose works better, so that idea is unproven.[6] We found no trial that tested the best time of day to take it.
Is a nattokinase supplement the same as eating natto?
No. Natto the food contains nattokinase but also a large amount of vitamin K, while some nattokinase extracts have the vitamin K2 removed.[3][11] That difference matters most for people on warfarin.
The NIH Office of Dietary Supplements lists 3 ounces of natto at about 850 mcg of vitamin K, as MK-7. That is 708 percent of the Daily Value.[11] The same fact sheet warns that vitamin K “can have a serious and potentially dangerous interaction with anticoagulants such as warfarin.”[11]
The 2016 blood pressure trial used an extract from which vitamin K2 had been removed.[3] Not every product says whether it did the same, so read the label or ask the maker. You can find more on how other compounds compare on our supplement ingredients guide.
What do doctors use first for high blood pressure?
For high blood pressure, the NHLBI says treatment may include heart-healthy lifestyle changes alone or together with medicines.[12] Nattokinase does not stand in for either one.
The lifestyle side includes the DASH eating plan. Medicines named by the NHLBI include diuretics, ACE inhibitors and calcium channel blockers.[12] Each has far more research behind it than nattokinase.
If your blood pressure is high, the first steps are a diagnosis, regular readings and a plan with your doctor. If you want to try nattokinase as well, bring it up at that visit, especially if you already take aspirin or a blood thinner.[9][12] For more reading on blood flow and blood vessels, see our circulation and heart health section.
Nattokinase label checklist
- Find the dose in FU. The trials report FU, so a label with only milligrams is hard to compare.[2][5]
- Check whether vitamin K2 has been removed, especially if you take warfarin.[3][11]
- Skip any product that claims to dissolve plaque or clots. The 3-year NAPS trial found no artery benefit.[5]
- Be wary of very high FU numbers sold as stronger. Higher doses are not shown to work better.[6]
- Tell your doctor and pharmacist before you start, and list every drug that affects clotting.[9]
- Keep checking your blood pressure at home or at the clinic so you can see if anything changes.[12]
- Compare the brand against our label and source checks before you buy.
Bottom line on nattokinase benefits
Nattokinase has some evidence for a small, short-term drop in blood pressure. The best long-term trial found it did nothing for artery thickening over 3 years, and the one larger positive study has design problems.[4][5][6]
For most people with high blood pressure, the DASH eating plan and the medicines a doctor prescribes are the better first step, because they have far stronger evidence.[12] If you take aspirin or any blood thinner, the bleeding risk is a good reason to leave nattokinase alone unless your doctor approves it.[9]
Frequently asked questions
What is a nattokinase supplement used for?
People mostly buy it for blood pressure and circulation. The best human evidence is a small blood pressure drop in short trials. A three-year trial found no effect on artery thickening, so claims about clearing arteries are not supported.
What is the best time to take nattokinase?
No trial we read tested a best time of day. Studies gave a daily dose without comparing morning and evening. If you use it, ask your doctor how it fits with other medicines, especially aspirin or blood thinners.
Are there nattokinase benefits for women?
We found no trials run only in women. The blood pressure trials included adults of both sexes, and one 2016 trial saw a larger drop in men. There is no safety data for pregnancy or breastfeeding.
How do I pick the best nattokinase supplement?
Look for a dose listed in FU, a note on whether vitamin K2 was removed, and no claims about dissolving plaque or clots. Higher FU numbers are not shown to work better. Check with your doctor before buying.
Can nattokinase replace blood pressure medicine?
No. Its effect in trials was a few mmHg over 8 weeks. The NHLBI lists lifestyle changes and medicines such as diuretics and ACE inhibitors as treatment. Keep taking a prescribed medicine unless your doctor changes it.
Sources
- Nattokinase: An Oral Antithrombotic Agent for the Prevention of Cardiovascular Disease. International Journal of Molecular Sciences, Weng et al., 2017
- Effects of nattokinase on blood pressure: a randomized, controlled trial. Hypertension Research, Kim et al., 2008
- Consumption of nattokinase is associated with reduced blood pressure and von Willebrand factor. Integrated Blood Pressure Control, Jensen et al., 2016
- Nattokinase Supplementation and Cardiovascular Risk Factors: a meta-analysis of randomized controlled trials. Reviews in Cardiovascular Medicine, Li et al., 2023
- Nattokinase atherothrombotic prevention study (NAPS): a randomized controlled trial. Clinical Hemorheology and Microcirculation, Hodis et al., 2021
- Effective management of atherosclerosis progress and hyperlipidemia with nattokinase. Frontiers in Cardiovascular Medicine, Chen et al., 2022
- A single-dose of oral nattokinase potentiates thrombolysis and anti-coagulation profiles. Scientific Reports, Kurosawa et al., 2015
- Effects of nattokinase on C-EPI closure time, PT and aPTT. Food and Function, Yoo et al., 2019
- Cerebellar hemorrhage provoked by combined use of nattokinase and aspirin. Internal Medicine, Chang et al., 2008
- Nattokinase supplementation for cognitive enhancement in asymptomatic intracranial and carotid stenosis (ICC-PACS). Journal of Stroke and Cerebrovascular Diseases, Zhang et al., 2026
- Vitamin K: Fact Sheet for Health Professionals. NIH Office of Dietary Supplements
- High Blood Pressure: Treatment. National Heart, Lung, and Blood Institute
Maya Ellison is the Reviews Editor at The Well Brew, a slow, plain-language supplement review blog for everyday adults. Maya reads each label in full, sets every dose beside the amounts used in human studies, grades the research with sources such as the NIH Office of Dietary Supplements and NCCIH, and works out the real cost and refund fine print. Maya has no medical credentials and is not a doctor, dietitian, nurse or pharmacist. Reviews give pros, cons and who a product suits, never scores. How we review supplements.
This article is general information, not medical advice. Dietary supplements are not reviewed by the FDA for safety or effectiveness before they are sold. Talk to your doctor before you start any supplement, especially if you are pregnant, nursing, take medication or have a health condition.