Does Nattokinase Lower Blood Pressure?

If you've been managing blood pressure — or trying to keep it from creeping higher — you've probably come across nattokinase. It shows up in supplement recommendations, health forums, and the occasional headline promising "natural blood pressure support." But when you dig into the claims, the picture gets murky fast. Some sources cite clinical trials with impressive numbers. Others warn about dangerous interactions with medications.

So does nattokinase actually lower blood pressure, or is it another overhyped supplement?

We reviewed the clinical trials, meta-analyses, and safety data to answer that question as clearly as the evidence allows. This guide covers what nattokinase is, how it may affect blood pressure, the specific numbers from controlled studies, detailed safety information (including drug interactions most guides skip), and insights from Japanese research — where nattokinase was originally discovered and has been studied the longest.

Whether you're considering nattokinase alongside your current regimen or exploring natural options for the first time, this guide gives you the evidence you need to make an informed decision with your healthcare provider.

What Is Nattokinase?

Nattokinase is a fibrinolytic enzyme — meaning it can break down fibrin, a protein involved in blood clotting. It was first identified in natto, a traditional Japanese food made from soybeans fermented with the bacterium Bacillus subtilis var. natto ^[6].

The discovery happened in 1980, when Japanese researcher Dr. Hiroyuki Sumi placed a piece of natto on artificial fibrin in a petri dish. He observed the fibrin dissolving dramatically — faster than any other natural compound he had tested. He named the enzyme responsible "nattokinase" ^[8].

Nattokinase supplements are not the same as eating natto. Supplements contain a purified extract of the enzyme, standardized by activity level measured in fibrinolytic units (FU). A typical supplement provides 2,000 FU per serving. Importantly, most nattokinase supplements have had vitamin K2 removed — a key distinction from whole natto, which is rich in vitamin K2 and can interfere with blood-thinning medications like warfarin.

The enzyme itself is a serine protease with a molecular weight of approximately 27.7 kDa and 275 amino acid residues ^[6]. While that's technical detail most people don't need, it matters for one reason: nattokinase is a relatively large molecule, which raises questions about how much of it survives digestion and reaches the bloodstream — a point we'll address when examining the clinical evidence.

What the Clinical Evidence Shows

Meta-Analysis Results: Moderate Evidence

The most comprehensive look at nattokinase and blood pressure comes from a systematic review and meta-analysis published in Reviews in Cardiovascular Medicine. Researchers pooled data from 6 randomized controlled trials involving 546 participants ^[2].

The results:

• Systolic blood pressure reduced by an average of 3.45 mmHg (95% CI: -4.37 to -2.18, p<0.00001)
• Diastolic blood pressure reduced by an average of 2.32 mmHg (95% CI: -2.72 to -1.92, p<0.00001)

Both reductions were statistically significant across the pooled studies. To put those numbers in context, epidemiological data suggests that even a 5 mmHg reduction in systolic blood pressure is associated with roughly a 10% lower risk of major cardiovascular events at the population level. So while the numbers may seem small on a blood pressure monitor, they represent a meaningful shift in cardiovascular risk — particularly for people hovering near hypertension thresholds.

It's worth noting what the meta-analysis also found about nattokinase's effects beyond blood pressure. The review reported that nattokinase supplementation was associated with favorable changes in certain coagulation markers, including increased collagen-epinephrine closure time and activated partial thromboplastin time — suggesting the enzyme affects the blood clotting system broadly, not just blood pressure in isolation ^[2].

The Landmark Trial

The most frequently cited study is a randomized, double-blind, placebo-controlled trial published in Hypertension Research (a Nature journal). Eighty-six participants with pre-hypertension or stage 1 hypertension (systolic BP 130-159 mmHg) took either 2,000 FU of nattokinase or placebo daily for 8 weeks ^[1].

Key findings:

• Systolic BP reduced by 5.55 mmHg (95% CI: -10.5 to -0.57, p<0.05)
• Diastolic BP reduced by 2.84 mmHg (95% CI: -5.33 to -0.33, p<0.05)
• Renin activity decreased by 1.17 ng/mL/h (p<0.05)

The renin reduction is notable because renin is a key enzyme in the system that regulates blood pressure. Lower renin activity suggests nattokinase may influence blood pressure through a specific physiological pathway, not just a general effect.

A North American Multicenter Trial

A separate randomized, double-blind, placebo-controlled trial conducted across multiple sites in North America studied nattokinase in a hypertensive population with diverse genetic, dietary, and lifestyle backgrounds ^[3].

Key findings:

• Diastolic BP in the nattokinase group was significantly lower than placebo (84 ± 1.9 mmHg vs 87 ± 1.7 mmHg, p<0.01)
• Von Willebrand factor — a cardiovascular risk marker — decreased by 15% in hypertensive participants

This study is important because it tested nattokinase in a non-Japanese population, suggesting the effects aren't limited to specific genetic or dietary backgrounds.

The Study That Didn't Show Results

Honesty about evidence requires mentioning the Nattokinase Atherothrombotic Prevention Study (NAPS) — the longest controlled nattokinase trial to date. This randomized study followed participants for a median of 3 years ^[4].

The result: no significant effect on blood pressure compared to placebo.

This creates important nuance. Short-term studies (8-12 weeks) consistently show modest reductions, but the only long-term study did not confirm that these effects persist. The NAPS study focused primarily on atherosclerosis progression rather than blood pressure as its main outcome, so it may not have been optimally designed to detect BP effects — but the finding cannot be ignored.

Bottom line: The evidence for nattokinase lowering blood pressure is moderate. Short-term effects are real but modest (3-5 mmHg). Long-term data is insufficient to confirm lasting benefits. More large-scale, long-duration trials are needed.

How Nattokinase May Lower Blood Pressure

Research suggests nattokinase may influence blood pressure through several mechanisms, though not all are equally well-supported in human studies.

Fibrinolytic Activity: Strong Evidence

Nattokinase directly dissolves fibrin — a protein that forms the structural framework of blood clots. By breaking down fibrin, nattokinase may reduce blood viscosity and lower resistance in blood vessels ^[7]. This fibrinolytic activity has been described as comparable to or greater than plasmin, the body's own clot-dissolving enzyme ^[6].

Why this matters for blood pressure: When blood flows more easily through less obstructed vessels, the heart doesn't need to pump as hard — potentially lowering blood pressure.

Renin Activity Reduction: Moderate Evidence

In the landmark clinical trial, nattokinase supplementation reduced plasma renin activity by 1.17 ng/mL/h ^[1]. Renin is part of the renin-angiotensin-aldosterone system (RAAS) — the same system that many blood pressure medications target. Lower renin activity means less angiotensin II production, which leads to less blood vessel constriction.

ACE Inhibition: Preliminary Evidence

Animal studies suggest nattokinase contains peptides that inhibit angiotensin-converting enzyme (ACE) — the same mechanism used by ACE inhibitor medications like lisinopril and ramipril. Research in spontaneously hypertensive rats showed dose-dependent ACE inhibition from natto extract ^[9].

However, ACE inhibition has not been directly measured in human blood pressure trials. The animal data is promising but should not be presented as proven in humans.

Von Willebrand Factor Reduction: Moderate Evidence

Von Willebrand factor (VWF) is a protein involved in blood clotting and a recognized cardiovascular risk marker. In the North American multicenter trial, nattokinase reduced VWF levels by 15% in hypertensive participants ^[3]. Elevated VWF levels are associated with increased cardiovascular risk, so this reduction — while not directly a blood pressure mechanism — suggests nattokinase may improve vascular health more broadly.

How These Mechanisms Work Together

The current understanding is that nattokinase may lower blood pressure through a combination of effects: reducing blood viscosity through fibrinolysis, influencing the renin-angiotensin system, and potentially improving vascular function markers. No single mechanism fully explains the observed blood pressure reductions in clinical trials, which suggests a multi-pathway effect rather than a single-target mechanism ^[14].

Dosage, Timing, and How to Take It

FU (Fibrinolytic Units) is the standard measure of nattokinase activity. When choosing a supplement, look for FU on the label rather than milligrams alone — two products with the same milligram amount can have very different activity levels.

What the research doesn't tell us: Optimal timing (morning vs evening), whether to take with or without food, and whether higher doses produce proportionally greater effects. These questions have not been directly studied in controlled trials.

One practical consideration: since nattokinase has fibrinolytic effects that may influence blood viscosity over several hours, some practitioners suggest taking it in the morning when cardiovascular risk tends to be highest. However, this is a theoretical recommendation, not one supported by head-to-head timing studies.

Quality markers to look for on labels: Choose supplements that list FU (fibrinolytic units) on the label, specify vitamin K2 removal (especially if you take blood thinners), and ideally carry JNKA certification or NSK-SD designation. These quality signals indicate adherence to the most established nattokinase manufacturing standards.

How Long Until You See Results?

Based on clinical trial data, measurable blood pressure changes appeared after 8 weeks of consistent daily supplementation at 2,000 FU ^[1].

Practical guidance:

• Don't expect overnight results. Blood pressure changes from nattokinase are gradual, not immediate
• Monitor your blood pressure regularly during supplementation — this is the only way to know if it's working for you
• 8-12 weeks is a reasonable trial period before evaluating whether nattokinase is having an effect
• The effects are modest — typically 3-5 mmHg systolic. If your blood pressure requires significant reduction, nattokinase alone is unlikely to be sufficient
• Keep perspective on the magnitude — a 3-5 mmHg reduction may be meaningful for borderline hypertension but is unlikely to replace medication for established hypertension
• Talk to your doctor before starting, especially if you're already on blood pressure medication

Safety and Side Effects

Overall Safety Profile

Clinical trials report a favorable safety profile for nattokinase at standard doses. A toxicological assessment conducted under Good Laboratory Practice (GLP) standards found no adverse effects at doses up to 1,000 mg/kg/day in rats — roughly 100 times the standard human dose — and no toxicologic concerns in human volunteers at 10 mg/kg for 28 days ^[10].

A large clinical study involving 1,062 participants found no toxic side effects from nattokinase supplementation ^[12].

In the meta-analysis of 6 RCTs, no notable adverse events were reported across all included studies, and compliance rates exceeded 95%, indicating good tolerability ^[2].

Gastrointestinal Effects

Gastrointestinal side effects appear rare. In a 189-patient randomized trial, only one case of abdominal discomfort was reported in the nattokinase group — and one case was also reported in the placebo group, suggesting it may not have been related to nattokinase ^[5].

Drug Interactions — Critical Safety Information

This is where careful attention is needed. Nattokinase has fibrinolytic (clot-dissolving) activity, which means it can interact with medications that also affect blood clotting or blood pressure.

An observational clinical trial in patients with vascular diseases found that nattokinase administered alongside anticoagulant medications did not produce adverse drug reactions — but this was closely monitored with regular INR testing, renal function monitoring, and clinical assessments ^[11]. This is not a green light for self-experimentation. The study reinforces that combination use requires medical oversight with proper monitoring protocols.

It's also important to note that case reports of bleeding complications with nattokinase have been documented, though they are rare. A systematic review noted that "several case studies have recently emerged that provide contradictory findings on allergic and bleeding risks of nattokinase" — underscoring the importance of individual medical assessment before starting supplementation ^[2].

Who Should Avoid Nattokinase

• People taking blood thinners (warfarin, heparin, aspirin, clopidogrel) — unless specifically approved and monitored by their doctor
• Anyone scheduled for surgery — stop nattokinase at least 2 weeks before any surgical procedure due to its fibrinolytic effects
• People with bleeding disorders — nattokinase may worsen bleeding tendencies
• Pregnant or nursing women — insufficient safety data exists for these populations
• People with soy allergies — nattokinase is derived from fermented soybeans

Realistic Expectations

Nattokinase is not a replacement for prescribed blood pressure medication. The clinical evidence shows modest reductions of 3-5 mmHg — meaningful for borderline or mildly elevated blood pressure, but insufficient for moderate or severe hypertension. It may serve as a complementary approach alongside lifestyle modifications (diet, exercise, stress management), but always with your healthcare provider's knowledge and approval.

From Fermented Soybeans to Clinical Research: The Japanese Origins of Nattokinase

Nattokinase is one of the few supplements where the Japanese research heritage directly matters for the quality of what you buy. Here's what most English-language guides don't cover.

A Discovery Born From Traditional Food Science

Nattokinase wasn't identified in a pharmaceutical lab — it came from studying a food that Japanese people have eaten for over 1,000 years. Natto, made by fermenting soybeans with Bacillus subtilis, has been a traditional breakfast staple in Japan, long associated with cardiovascular health and longevity in Japanese dietary patterns ^[16].

Dr. Hiroyuki Sumi's 1980 discovery at Okayama Prefectural University of Science launched decades of Japanese research into nattokinase's mechanisms — research that English-language clinical trials later built upon ^[8].

Why this matters: The clinical research you read about in English-language studies often traces back to Japanese foundational work. Understanding this lineage helps evaluate the supplement's credibility — it's grounded in decades of systematic research, not a recent trend.

The Vitamin K2 Problem — and the Japanese Solution

Here's a practical concern that rarely gets adequate attention in English-language nattokinase guides. Whole natto is naturally rich in vitamin K2 (specifically MK-7). Vitamin K2 promotes blood clotting — the exact opposite of nattokinase's fibrinolytic effect. More critically, vitamin K2 directly interferes with warfarin, a widely prescribed blood thinner.

Japanese manufacturers developed NSK-SD — a patented purification process by Japan Bio Science Laboratory (JBSL) that selectively removes vitamin K2 from nattokinase extracts while preserving the enzyme's fibrinolytic activity. The Japan Nattokinase Association (JNKA) sets quality standards requiring vitamin K2 removal and minimum purity of 20,000 FU per gram ^[17].

Why this matters: If you're taking warfarin or any blood thinner, whether your nattokinase supplement has been processed to remove vitamin K2 is a critical safety consideration. Look for supplements that specify vitamin K2 removal or NSK-SD on the label.

A Regulatory Framework That Supports Research Claims

In Japan, nattokinase supplements can be registered as functional foods with function claims (機能性表示食品) through the Consumer Affairs Agency (消費者庁). This system, established in 2015, requires manufacturers to submit clinical evidence supporting their health claims — a more rigorous process than the supplement regulation framework in many international markets ^[18].

Why this matters: Japanese nattokinase supplements that carry functional food claims have undergone evidence review by a regulatory body. This doesn't guarantee the claims are correct, but it does mean the manufacturer had to present clinical data rather than relying solely on structure/function claims. For international consumers, this regulatory recognition provides an additional layer of confidence beyond what's available for most supplements in other markets.

The natto market itself reflects growing interest. Japanese domestic natto consumption reached 2,184 billion yen, representing a 26% increase over a five-year period, and nattokinase supplement exports from Japan grew by 150% year-over-year in the first half of a recent reporting period ^[16]. This growth signals both domestic confidence in nattokinase products and increasing international demand.

Quality Standardization Through JNKA

The Japan Nattokinase Association (JNKA) established industry standards for nattokinase purity, activity measurement, and vitamin K2 absence. JNKA-certified products meet minimum thresholds for enzyme activity and undergo standardized testing ^[17].

Why this matters: When evaluating nattokinase supplements, JNKA certification or NSK-SD designation provides a quality signal. Not all nattokinase products are manufactured to the same standards, and these certifications indicate adherence to the most established quality framework.

Our Recommendations

Japanese Nattokinase 4000

Why We Selected This: This supplement provides 4,000 FU per serving — double the standard clinical trial dosage of 2,000 FU. Manufactured in Japan with quality controls aligned with the standards that the Japanese nattokinase industry was built on. We chose it for customers who want a higher-potency option backed by Japanese manufacturing heritage.

The 4,000 FU dosage falls within the range studied in clinical research (2,000-10,000 FU), where no serious adverse effects have been reported. For people who want to start at the standard clinical trial dose, taking half a serving provides approximately 2,000 FU.

View Japanese Nattokinase 4000 →

Nattokinase EX

Why We Selected This: A comprehensive cardiovascular support formula that combines nattokinase with complementary ingredients for circulation support. For customers who want a multi-ingredient approach to cardiovascular wellness rather than nattokinase alone.

This option is well-suited for people interested in broader circulatory support beyond blood pressure specifically, combining the fibrinolytic benefits of nattokinase with additional cardiovascular-supporting ingredients.

View Nattokinase EX →

Conclusion

The clinical evidence shows that nattokinase can modestly reduce blood pressure — with meta-analysis data supporting a reduction of approximately 3-5 mmHg systolic and 2-3 mmHg diastolic over 8-12 weeks. These effects are statistically significant and clinically meaningful for people with mildly elevated blood pressure, but they do not approach the efficacy of prescription medications.

The key points from our review: the standard clinical trial dose is 2,000 FU per day; nattokinase must not be combined with blood thinners without medical supervision; the longest controlled study (3 years) did not find sustained blood pressure effects; and Japanese quality certifications like JNKA and NSK-SD provide meaningful quality signals when choosing a supplement.

Nattokinase is best suited as a complementary approach for people with borderline blood pressure who are already pursuing lifestyle modifications — not as a standalone treatment. As with any supplement that affects cardiovascular function, the conversation starts with your healthcare provider.

This article is for informational purposes only and does not constitute medical advice. Consult a healthcare professional before starting any new health regimen, especially if you have existing health conditions or take medications. Statements about dietary supplements have not been evaluated by the FDA and are not intended to diagnose, treat, cure, or prevent any disease.