Nattokinase for Heart Health and Blood Clots: What the Research Shows

Introduction

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Nattokinase is a serine protease enzyme extracted from natto, a traditional Japanese food made from soybeans fermented with the bacterium Bacillus subtilis var. natto. The enzyme was first identified in 1987 by Dr. Hiroyuki Sumi at the University of Chicago when he placed natto on artificial fibrin (the protein that forms the structural framework of blood clots) in a petri dish and observed it dissolve the fibrin completely within 18 hours. That observation launched decades of research into whether this enzyme could meaningfully impact human cardiovascular health.

The interest is understandable. Cardiovascular disease remains the leading cause of death worldwide, killing roughly 17.9 million people annually according to the World Health Organization. A significant proportion of cardiovascular events – heart attacks, strokes, pulmonary embolisms – involve the formation of blood clots (thrombi) that block critical blood vessels. Any compound that can safely dissolve clots or prevent their formation without the bleeding risks of pharmaceutical anticoagulants would represent a meaningful advance.

Nattokinase has genuine, measurable biological activity. It is not a vague “heart health” supplement with hand-waving mechanisms. Clinical studies have documented its effects on fibrinolysis, blood pressure, coagulation parameters, and lipid profiles. But the evidence is also more nuanced than supplement marketing suggests. Some effects are well-established. Others require much higher doses than typical supplements provide. And certain populations face serious safety risks.

This article covers the full picture: what nattokinase actually does in your body, what the clinical trials show (including the studies that found no benefit), practical dosing guidance, who should and should not take it, and the body signals that help you track whether it is working for you. Every claim is backed by published research, and every limitation is stated honestly.

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What Is Nattokinase and Where Does It Come From?

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Natto has been consumed in Japan for over 1,000 years. It is made by steaming soybeans and fermenting them with Bacillus subtilis var. natto, which produces a sticky, stringy, pungent food that is an acquired taste for most Westerners. The fermentation process generates several bioactive compounds, including nattokinase, vitamin K2 (menaquinone-7), polyamines, and beneficial bacteria.

Nattokinase is a subtilisin-like serine protease with a molecular weight of approximately 27.7 kDa, consisting of 275 amino acid residues. Despite its name, nattokinase is not a kinase (an enzyme that transfers phosphate groups). The name is a historical misnomer that has persisted. It is a protease – an enzyme that breaks down proteins, specifically the fibrin protein that gives blood clots their structural integrity.

A critical distinction: Nattokinase supplements are not the same as eating natto. Whole natto contains extremely high levels of vitamin K2 – over 880 mcg per 100 grams, primarily as MK-7. Vitamin K2 promotes blood clotting by activating clotting factors. This creates a paradox: natto contains both a clot-dissolving enzyme (nattokinase) and a clot-promoting vitamin (K2). Reputable nattokinase supplements, particularly those using the NSK-SD formulation, have the vitamin K2 removed through ultrafiltration. This is essential for anyone taking the supplement specifically for its anticoagulant or fibrinolytic properties, and absolutely critical for anyone on warfarin or other vitamin K-sensitive medications.

How Nattokinase Works: The Biology of Fibrinolysis

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Understanding why nattokinase generates scientific interest requires a brief look at how your body manages blood clots.

The Clotting-Fibrinolysis Balance

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Your body maintains a constant balance between clot formation (coagulation) and clot breakdown (fibrinolysis). When you cut yourself, a cascade of clotting factors activates to form a fibrin mesh that traps platelets and red blood cells, creating a clot that stops bleeding. Once the wound heals, your body dissolves the clot through fibrinolysis – a process driven primarily by the enzyme plasmin, which is activated from its inactive precursor plasminogen by tissue plasminogen activator (t-PA).

Problems arise when this balance tips too far in either direction. Excessive clotting (hypercoagulability) can lead to deep vein thrombosis, pulmonary embolism, stroke, or heart attack. Insufficient clotting leads to excessive bleeding. Many cardiovascular conditions, including atherosclerosis, diabetes, obesity, and chronic inflammation, shift the balance toward hypercoagulability.

Nattokinase’s Multiple Mechanisms

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What makes nattokinase particularly interesting from a pharmacological standpoint is that it does not work through just one mechanism. Research has identified at least four distinct ways nattokinase affects the clotting-fibrinolysis balance (Chen et al., 2018):

1. Direct fibrinolysis: Nattokinase directly hydrolyzes (breaks down) fibrin, the structural protein of blood clots. Unlike pharmaceutical thrombolytics such as t-PA, which work indirectly by activating plasminogen, nattokinase can break down fibrin directly. This was Dr. Sumi’s original observation.

2. Plasminogen activation: Nattokinase converts inactive plasminogen into active plasmin, amplifying your body’s own clot-dissolving capacity. It also converts pro-urokinase to urokinase, another activator of plasminogen. This means nattokinase boosts your endogenous fibrinolytic system rather than merely acting as an external agent.

3. Inhibition of PAI-1: Plasminogen activator inhibitor-1 (PAI-1) is a protein that blocks t-PA, your body’s natural clot dissolver. Elevated PAI-1 levels are associated with increased cardiovascular risk. Nattokinase degrades PAI-1, effectively removing a brake on your body’s natural fibrinolytic process.

4. Enhancement of t-PA: Nattokinase increases the production and activity of tissue plasminogen activator (t-PA), the primary driver of endogenous fibrinolysis.

This multi-pronged mechanism distinguishes nattokinase from single-mechanism agents. It does not just dissolve clots – it shifts the entire clotting-fibrinolysis balance toward reduced clotting through at least four simultaneous pathways. From a biological standpoint, this is a more comprehensive intervention than many people realize.

Beyond Fibrinolysis: Additional Cardiovascular Mechanisms

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More recent research has identified additional mechanisms that extend beyond simple clot dissolution:

• Blood viscosity reduction: Nattokinase has been shown to reduce blood viscosity, which may improve blood flow through narrowed arteries independently of its fibrinolytic effects.

• Angiotensin-converting enzyme (ACE) inhibition: Some evidence suggests nattokinase may inhibit ACE, the same enzyme targeted by pharmaceutical ACE inhibitors used to treat high blood pressure. This provides a plausible mechanism for its blood pressure-lowering effects.

• HMG-CoA reductase inhibition: Research published in Nutrients in 2025 found that nattokinase may inhibit HMG-CoA reductase, the same enzyme targeted by statin drugs, which could explain some of its lipid-lowering effects at higher doses (Nutrients, 2025).

• Lipoprotein lipase enhancement: Nattokinase appears to enhance the activity of lipoprotein lipase, an enzyme that breaks down triglycerides in the bloodstream.

What the Clinical Research Shows

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Let us examine the human clinical trial data systematically, organized by the cardiovascular outcome being studied.

Fibrinolytic and Anticoagulant Activity

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The most direct evidence for nattokinase’s clot-related activity comes from a well-designed 2015 study published in Scientific Reports (Kurosawa et al., 2015). This was a double-blind, placebo-controlled, crossover study in 12 healthy young males who received either a single 2,000 FU dose of nattokinase or placebo, with blood samples taken at 2, 4, 6, and 8 hours.

Key findings:

• D-dimer levels (a marker of clot breakdown) were significantly elevated at 6 and 8 hours after nattokinase administration
• Fibrin/fibrinogen degradation products (FDP) were significantly elevated at 4 hours
• Factor VIII activity (a clotting factor) declined at 4 and 6 hours
• Antithrombin concentrations were higher at 2 and 4 hours

These findings confirm that a single oral dose of nattokinase produces measurable fibrinolytic and anticoagulant effects in humans within hours. The changes in D-dimer and FDP indicate that existing fibrin is being broken down. The reduction in Factor VIII and increase in antithrombin indicate an overall shift toward reduced coagulation.

However, the study authors noted an important limitation: these are biomarker changes, not clinical outcomes. We know nattokinase changes clotting parameters, but no randomized controlled trial has yet demonstrated that these changes translate into fewer heart attacks, strokes, or venous thromboembolisms.

Blood Pressure

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The blood pressure evidence is arguably the most consistent finding in the nattokinase research literature. A 2024 systematic review and meta-analysis published in Reviews in Cardiovascular Medicine (Gallelli et al., 2024) pooled data from six randomized controlled trials with a total of 546 participants. The results showed:

• Systolic blood pressure reduction: -3.45 mmHg (95% CI: -4.37 to -2.18)
• Diastolic blood pressure reduction: -2.32 mmHg (95% CI: -2.72 to -1.92)

An earlier randomized, controlled trial published in Hypertension Research (Kim et al., 2008) specifically examined the blood pressure effects of nattokinase in 86 participants with pre-hypertension or stage 1 hypertension. After 8 weeks of supplementation with 2,000 FU/day:

• Systolic blood pressure decreased by 5.55 mmHg compared to placebo
• Diastolic blood pressure decreased by 2.84 mmHg compared to placebo

A 3-5 mmHg reduction in systolic blood pressure may seem modest, but at a population level, a sustained 5 mmHg reduction in systolic blood pressure is associated with approximately a 14% reduction in stroke risk and a 9% reduction in coronary heart disease events (Ettehad et al., 2016). For people with borderline or mildly elevated blood pressure who prefer to try a natural approach before committing to pharmaceuticals, this is a clinically meaningful effect.

The proposed mechanism for blood pressure reduction involves nattokinase’s ability to cleave plasma fibrinogen after absorption in the small intestine, which reduces blood viscosity. Additionally, nattokinase may inhibit angiotensin-converting enzyme (ACE), providing a pharmacological mechanism similar to ACE inhibitor medications like lisinopril and enalapril.

The NAPS Trial: Atherosclerosis Prevention

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The largest and most rigorously designed nattokinase study to date is the Nattokinase Atherothrombotic Prevention Study (NAPS), a double-blind, placebo-controlled trial conducted at the University of Southern California (Ren et al., 2021). This was a phase 2 clinical trial that randomized 265 individuals (median age 65.3 years) without clinical cardiovascular disease to either 2,000 FU/day of nattokinase or placebo, with a median follow-up of 3 years.

The primary outcome was the rate of change in subclinical atherosclerosis, measured by serial carotid ultrasound assessing carotid artery intima-media thickness (CIMT) and carotid arterial stiffness (CAS) every 6 months.

The result was negative: After 3 years of supplementation, the annualized rate of change in CIMT and CAS did not significantly differ between the nattokinase and placebo groups.

This is an important finding that deserves honest discussion. The NAPS trial is the gold standard study for nattokinase and atherosclerosis, and it found no benefit at the standard supplemental dose of 2,000 FU/day for slowing the progression of subclinical atherosclerosis over 3 years.

However, a separate study paints a more nuanced picture. A retrospective Chinese study of 1,062 participants published in Frontiers in Cardiovascular Medicine (Ji et al., 2022) found that after 12 months of nattokinase at a much higher dose of 10,800 FU/day, carotid intima-media thickness decreased significantly (from 1.33 mm to 1.04 mm on average, P < 0.001), with plaque size decreasing by up to 36%.

The critical difference is dose: 2,000 FU/day showed no effect on atherosclerosis, while 10,800 FU/day (over 5 times higher) showed significant improvement. However, the Chinese study was retrospective and uncontrolled, meaning patients who chose nattokinase may have differed systematically from those who did not. Without randomization, these results cannot establish causation. Still, the dose-dependent pattern is noteworthy and warrants further investigation in randomized trials.

Lipid Effects: Cholesterol and Triglycerides

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The evidence for nattokinase’s effects on blood lipids is mixed and appears heavily dose-dependent.

The 2024 meta-analysis by Gallelli et al. examined three studies with 134 participants and found no significant effect of nattokinase on triglyceride levels. Similarly, no significant differences were found in HDL cholesterol or LDL cholesterol levels at standard supplemental doses.

However, a 2024 randomized, double-blind, placebo-controlled trial published in Frontiers in Nutrition examined nattokinase combined with red yeast rice in 178 patients with stable coronary artery disease over 90 days (Liu et al., 2024). The study randomized participants to four groups: nattokinase plus red yeast rice, nattokinase alone, red yeast rice alone, and placebo.

Key findings:

• The nattokinase + red yeast rice combination showed the maximum effect: triglycerides decreased by 0.39 mmol/L, total cholesterol decreased by 0.66 mmol/L, diastolic blood pressure decreased by 7.39 mmHg, and HDL cholesterol increased by 0.195 mmol/L
• Nattokinase alone showed more modest lipid changes but still contributed to blood pressure reduction and fibrinolytic improvement
• No adverse effects were reported in any group

The retrospective Chinese study mentioned above (Ji et al., 2022) at 10,800 FU/day showed more pronounced lipid improvements, but lower doses (3,600 FU/day) were found to be ineffective for lipid lowering.

The bottom line on lipids: At standard supplemental doses (2,000 FU/day), nattokinase does not appear to meaningfully improve cholesterol or triglycerides. Higher doses (10,800 FU/day) or combination therapy with red yeast rice may produce significant lipid changes, but this requires further study in well-controlled trials. If your primary goal is lowering cholesterol or triglycerides, nattokinase alone at standard doses is not the right tool. Consider omega-3 fatty acids, berberine, or pharmaceutical statins depending on the severity of your dyslipidemia.

Nattokinase and Long COVID Microclots

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One of the most compelling emerging areas of nattokinase research involves its potential role in addressing the anomalous blood clots associated with Long COVID. Researchers have identified that in some Long COVID patients, fibrinogen polymerizes into an unusual amyloid form, creating what are called “fibrinaloid microclots.” These microclots are resistant to normal fibrinolysis, meaning the body’s standard clot-dissolving machinery cannot break them down effectively. They may contribute to persistent fatigue, brain fog, exercise intolerance, and other Long COVID symptoms by impeding microcirculation.

A 2024 study from the University of Liverpool and Stellenbosch University (Pretorius et al., 2024) used automated microscopy to demonstrate that recombinant nattokinase effectively degrades fibrinaloid microclots in vitro, with a half-life to noticeable clot reduction of approximately 2 hours. This is significant because these microclots are specifically resistant to the body’s normal fibrinolytic processes – nattokinase’s ability to directly hydrolyze fibrin (rather than relying solely on the plasminogen pathway) may be particularly relevant here.

Important context: This is in vitro (laboratory) research, not a clinical trial. No randomized controlled trial has yet demonstrated that nattokinase improves clinical outcomes in Long COVID patients. Anecdotal reports from patients are numerous, and some clinicians have incorporated nattokinase into Long COVID treatment protocols, but the evidence base is preliminary. Clinical trials are needed before definitive recommendations can be made.

Real-World Safety Data

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A 2021 study published in Nutrients examined the safety of nattokinase in real-world clinical use among patients with vascular diseases (Gallelli et al., 2021). The study found that the incidence of adverse reactions was very low, with only occasional minor gastrointestinal discomfort reported. No serious bleeding events were observed when nattokinase was used as directed and not combined with anticoagulant medications.

Toxicology data is also reassuring: no toxic effects have been observed in rats at doses of 22,000 FU/kg/day, which would be equivalent to approximately 1.43 million FU/day in humans – roughly 700 times the standard supplemental dose. In human studies, doses up to 14,000 FU/day have been used without safety concerns.

Clues Your Body Tells You: Signs of Cardiovascular and Clotting Issues

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Your cardiovascular system communicates its health status through a wide range of signals. Many of these get dismissed as “normal aging” or “stress,” but they may indicate that your clotting-fibrinolysis balance, blood pressure, or vascular health could benefit from attention.

Signs Something May Be Wrong

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Circulation-related signals:

• Cold hands and feet, even in warm environments
• Numbness or tingling in extremities
• Slow healing of cuts and bruises
• Varicose veins or spider veins that are worsening
• Swelling in ankles or lower legs, especially by evening
• Skin color changes in the lower legs (reddish-brown discoloration)
• Leg cramps or pain that worsens with walking and improves with rest (intermittent claudication)

Blood pressure-related signals:

• Morning headaches, particularly at the back of the head
• Dizziness or lightheadedness when standing up quickly
• Facial flushing
• Visual changes (blurry vision, spots)
• Ringing in the ears (tinnitus)
• Nosebleeds that are becoming more frequent
• Shortness of breath with mild exertion that was previously tolerable

General cardiovascular warning signs:

• Persistent fatigue that does not improve with rest
• Shortness of breath during activities that previously felt easy
• Chest tightness or pressure during physical exertion
• Heart palpitations or irregular heartbeat sensations
• Unexplained anxiety or sense of impending doom
• Difficulty concentrating or brain fog – which can be related to reduced cerebral blood flow

If you recognize a cluster of these symptoms, they warrant a conversation with your healthcare provider before starting any supplement, including nattokinase. Some of these symptoms can indicate conditions that require medical treatment, not supplementation.

What Improvement Looks Like: Body Signals When Nattokinase Is Working

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Based on the pharmacological actions of nattokinase (improved fibrinolysis, reduced blood viscosity, lower blood pressure), here are the body signals that may indicate the supplement is having a beneficial effect:

Within the first 1-2 weeks:

• Hands and feet may feel warmer, especially in the evening – improved peripheral circulation is one of the earliest effects of reduced blood viscosity
• Mild improvement in energy levels, particularly in the afternoon
• Slightly easier breathing during mild physical activity
• Subtle reduction in the “heavy legs” feeling at the end of the day

At 4-8 weeks (blood pressure effects becoming measurable):

• Morning headaches less frequent or less intense
• Better exercise tolerance – you may notice that activities feel slightly easier
• Improved mental clarity, particularly in the afternoon – reduced blood viscosity may improve cerebral blood flow
• Blood pressure readings lower by 3-5 mmHg systolic if you monitor at home
• Fewer episodes of dizziness or lightheadedness
• Reduced ankle swelling

At 3-6 months:

• More consistent energy throughout the day
• Sustained improvement in exercise capacity
• If monitoring blood pressure, readings may stabilize at a lower baseline
• Some people report that bruises heal faster and are less extensive, consistent with improved microcirculation

Important note: These improvements are subtle, not dramatic. Nattokinase is not a medication that produces obvious, immediate effects in most people. If you have healthy cardiovascular function to begin with, you may not notice much of anything. The benefits are most noticeable in people who start with suboptimal cardiovascular markers – elevated blood pressure, poor circulation, high viscosity, or elevated fibrinogen levels.

Warning Signs to Watch For: When to See a Doctor Immediately

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Nattokinase is generally safe, but because it affects blood clotting, certain warning signs demand immediate medical attention:

Stop nattokinase and seek emergency care if you experience:

• Unusual bleeding – bleeding gums, blood in urine or stool, nosebleeds that do not stop within 15 minutes, unusually heavy menstrual bleeding, or bleeding from cuts that is difficult to control
• Signs of internal bleeding – severe headache of sudden onset (“thunderclap headache”), vision changes, confusion, slurred speech, vomiting blood, or black tarry stools
• Signs of a blood clot – sudden swelling, pain, warmth, and redness in one leg (deep vein thrombosis), sudden shortness of breath with chest pain (possible pulmonary embolism), sudden weakness or numbness on one side of the body (possible stroke)

• Severe drop in blood pressure – extreme dizziness, fainting, cold clammy skin, rapid heartbeat, confusion
• Allergic reaction – hives, swelling of the face/lips/tongue, difficulty breathing (rare but possible, especially in people with soy allergies)

See your doctor (non-emergency) if you notice:

• Bruising more easily or extensively than before
• Small red or purple spots on the skin (petechiae)
• Cuts that take noticeably longer to stop bleeding
• Persistent headaches that began after starting nattokinase
• Any new symptom that correlates temporally with starting the supplement

Timeline of Changes: What to Expect

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Dosing and Timing: A Practical Guide

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Understanding Fibrinolytic Units (FU)

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Nattokinase potency is measured in fibrinolytic units (FU), not milligrams. FU reflects how effectively the enzyme can break down fibrin – the higher the number, the greater the fibrinolytic activity. One FU roughly corresponds to 0.05 mg of nattokinase, so a 2,000 FU capsule contains approximately 100 mg of enzyme.

This distinction matters because a supplement listing “200 mg nattokinase” without specifying FU activity could have widely varying potency depending on the manufacturing process and enzyme quality.

Dose Recommendations by Goal

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General cardiovascular support and blood pressure:

• 2,000 FU per day – This is the dose used in the majority of clinical trials, including the NAPS study and the Kim et al. blood pressure trial. It is the standard recommended dose on most supplement labels and has the most safety data behind it.

Enhanced fibrinolytic activity:

• 4,000-6,000 FU per day – Some clinicians recommend higher doses for individuals with elevated fibrinogen levels, a history of clotting events (with doctor approval), or those seeking stronger fibrinolytic effects. Split into two doses (morning and evening) for more consistent blood levels.

Atherosclerosis management and lipid improvement (under medical supervision only):

• 10,800 FU per day – This is the dose used in the Ji et al. (2022) study that showed significant reductions in carotid intima-media thickness and plaque size. This dose should only be used with medical monitoring due to the increased fibrinolytic activity and potential for interaction with other medications.

Timing

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• Take nattokinase on an empty stomach or with a light meal. Unlike fat-soluble supplements such as CoQ10 or omega-3s, nattokinase is a water-soluble enzyme that does not require dietary fat for absorption.

• Morning dosing is most common in clinical studies. Some practitioners recommend splitting doses between morning and evening for higher daily intakes.

• If you are taking nattokinase for blood pressure: Consistency matters more than timing. Take it at the same time each day. Blood pressure effects build over weeks, not hours.

• If you are taking nattokinase for fibrinolytic effects: Some practitioners recommend evening dosing based on the rationale that clotting risk is highest in the early morning hours. A meta-analysis of cardiovascular events has shown that heart attacks and strokes are most likely to occur between 6 AM and noon, likely due to the morning surge in cortisol and catecholamines that promote coagulation. Taking nattokinase in the evening may provide peak fibrinolytic activity during this high-risk window, though no clinical trial has directly tested this timing strategy.

What to Look for in a Supplement

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Essential criteria:

• FU activity clearly stated – The label should specify fibrinolytic units, not just milligrams. A minimum of 2,000 FU per serving is the standard clinical dose.
• Vitamin K2 removed – Look for the designation “vitamin K2-free” or products using the NSK-SD formulation, which specifically removes vitamin K2 through ultrafiltration. This is critical if you take any anticoagulant medication.
• Third-party tested – ConsumerLab testing found that only 5 out of 8 nattokinase supplements tested delivered enzyme activity within an acceptable margin of their labeled amounts. Two products delivered far less than claimed. Choose brands verified by ConsumerLab, USP, or NSF.
• Soy allergen disclosure – Nattokinase is derived from soybeans. If you have a soy allergy, look for products that specify the final product has been purified to remove soy proteins, or avoid nattokinase entirely.

Reputable formulations:

• NSK-SD is a patented, clinically studied form produced by Japan Bio Science Laboratory (JBSL), the most extensively researched nattokinase ingredient with vitamin K2 removed. Brands using NSK-SD include Doctor’s Best and Pure Encapsulations.
• NOW Nattokinase provides 2,000 FU per serving with vitamin K removed and is a widely available, third-party tested option.

A Practical Nattokinase Protocol: Step by Step

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Week 1-2: Starting Phase

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1. Get a baseline: Before starting nattokinase, get your blood pressure measured (ideally at home, averaged over several readings). If possible, ask your doctor for baseline blood work including fibrinogen, D-dimer, lipid panel, and a complete blood count. These values give you objective markers to track.

2. Start at 2,000 FU/day: Take one capsule in the morning with water. There is no need to build up gradually – this is the standard clinical dose.

3. Watch for any adverse reactions: Pay attention to unusual bruising, bleeding gums, or nosebleeds. These are unlikely at 2,000 FU/day in healthy individuals but should be monitored.

4. Continue all current medications as prescribed: Do not reduce or stop any medication based on starting nattokinase. Only your doctor should make medication changes.

Weeks 2-4: Assessment Phase

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5. Track blood pressure: If you have a home blood pressure monitor, take readings at the same time each day (morning, before food or caffeine). Look for trends, not individual readings.

6. Note energy and circulation changes: Keep a brief daily note about energy levels, exercise tolerance, and extremity warmth. Patterns are easier to spot than single observations.

7. Continue daily dosing: Consistency is key. The blood pressure and cardiovascular effects build over weeks of regular use.

Weeks 4-8: Evaluation Phase

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8. Compare blood pressure to baseline: By 8 weeks, you should see a measurable trend if nattokinase is affecting your blood pressure. A reduction of 3-5 mmHg systolic is consistent with the clinical trial data.

9. Consider dose adjustment: If you have been tolerating 2,000 FU/day well and want to explore higher doses for enhanced fibrinolytic activity, discuss increasing to 4,000 FU/day (split morning and evening) with your healthcare provider.

10. Repeat blood work: Ask your doctor to repeat fibrinogen, D-dimer, and lipid panel to compare against your baseline. This provides objective data on whether nattokinase is affecting your specific markers.

Month 3 and Beyond: Maintenance Phase

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11. Settle into your maintenance dose: For most people, 2,000-4,000 FU/day is sufficient for ongoing cardiovascular support. Higher doses should be reserved for specific clinical situations under medical guidance.

12. Periodic monitoring: Get blood pressure checked at regular intervals. Repeat blood work every 6-12 months to track trends.

13. Reassess need: If you started nattokinase for borderline blood pressure and your readings have normalized with lifestyle changes, discuss with your doctor whether continued supplementation is necessary.

Common Myths About Nattokinase – Debunked

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Myth 1: “Nattokinase is a natural alternative to warfarin”

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Reality: This is dangerous misinformation. A published case report documents a patient with a mechanical aortic valve who substituted nattokinase 100 mg/day for warfarin and developed life-threatening valve thrombosis approximately one year later, requiring emergency valve replacement surgery (Chang et al., 2014). Nattokinase has measurable anticoagulant properties, but it is not a substitute for prescription anticoagulants. Warfarin, heparin, and direct oral anticoagulants have been dose-calibrated in massive clinical trials with validated monitoring protocols (like INR for warfarin). Nattokinase has no equivalent monitoring framework, and its potency is not standardized to the same degree. Never substitute nattokinase for a prescribed anticoagulant.

Myth 2: “Higher doses are always better”

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Reality: The dose-response relationship with nattokinase is real but complex. For blood pressure, 2,000 FU/day appears sufficient. For atherosclerosis and lipid effects, 10,800 FU/day was needed. But higher doses also carry higher bleeding risk. More is not automatically better – it depends on your goal and your risk profile. For most people, 2,000-4,000 FU/day represents the sweet spot of meaningful benefit with minimal risk.

Myth 3: “Nattokinase dissolves arterial plaque”

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Reality: The NAPS trial – the largest, most rigorous study – found no significant effect of 2,000 FU/day on carotid artery plaque over 3 years. The Chinese retrospective study showing plaque reduction used 10,800 FU/day and was not randomized. Nattokinase may influence atherosclerosis at very high doses, but claiming it “dissolves plaque” at standard supplemental doses is not supported by the strongest available evidence.

Myth 4: “Nattokinase is just another blood thinner”

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Reality: Nattokinase’s mechanism is fundamentally different from pharmaceutical blood thinners. Warfarin blocks vitamin K-dependent clotting factor synthesis. Heparin enhances antithrombin activity. Aspirin inhibits platelet aggregation. Nattokinase works primarily by enhancing fibrinolysis – the dissolution of formed clots – while also modulating several other pathways. It occupies a unique pharmacological space that overlaps with, but is distinct from, conventional anticoagulants and antiplatelets.

Myth 5: “Natto and nattokinase supplements are the same thing”

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Reality: Whole natto contains very high levels of vitamin K2, which promotes blood clotting – the opposite of what most people want from nattokinase supplementation. Purified nattokinase supplements (especially those using the NSK-SD formulation) have the vitamin K2 removed. This distinction is critical, particularly for people on warfarin, where consuming natto could dangerously reduce the drug’s effectiveness by providing massive amounts of vitamin K.

Myth 6: “Nattokinase cures Long COVID”

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Reality: The in vitro evidence that nattokinase can degrade fibrinaloid microclots is genuinely interesting and scientifically plausible. But no randomized clinical trial has demonstrated that nattokinase improves Long COVID symptoms. Anecdotal reports are encouraging but not proof. This is an area where the science is promising but preliminary. Using nattokinase for Long COVID is reasonable to discuss with your doctor, but claiming it as a cure is premature.

Who Should Consider Nattokinase – and Who Should Avoid It

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Good Candidates for Nattokinase

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• People with borderline or mild hypertension (systolic 120-139 mmHg) who want to try a natural approach before or alongside lifestyle modifications
• Individuals with elevated fibrinogen levels – fibrinogen above 400 mg/dL is associated with increased cardiovascular risk, and nattokinase’s fibrinolytic activity directly addresses this
• People with poor peripheral circulation who experience cold extremities, leg heaviness, or other signs of high blood viscosity
• Those with a family history of cardiovascular disease seeking additional preventive measures alongside diet, exercise, and medical care
• Long COVID patients – with the caveat that the evidence is still preliminary, nattokinase is one of the more physiologically plausible supplements being explored for microclot-related symptoms
• People taking high-cholesterol supplements who may benefit from adding a fibrinolytic component to their cardiovascular supplement regimen

Who Should NOT Take Nattokinase

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Absolute contraindications:

• People taking warfarin (Coumadin) or other vitamin K antagonists – Even vitamin K2-free nattokinase supplements alter coagulation parameters, creating an unpredictable interaction with warfarin dose management. The risk of either bleeding or inadequate anticoagulation is too high without careful medical monitoring.

• People taking direct oral anticoagulants (DOACs) such as apixaban (Eliquis), rivaroxaban (Xarelto), dabigatran (Pradaxa), or edoxaban (Savaysa) – The additive anticoagulant effect could increase bleeding risk. No clinical data exists on the safety of combining nattokinase with DOACs.

• People with bleeding disorders (hemophilia, von Willebrand disease, thrombocytopenia) – Nattokinase could exacerbate bleeding tendency.

• People with mechanical heart valves – The documented case of valve thrombosis when nattokinase was substituted for warfarin makes this an absolute contraindication for unsupervised use.

Relative contraindications (discuss with your doctor):

• People taking antiplatelet drugs (aspirin, clopidogrel/Plavix) – The combination may increase bleeding risk, though no catastrophic interactions have been documented. Your doctor may approve the combination with monitoring.

• Pre-surgical patients – Discontinue nattokinase at least 2 weeks before scheduled surgery due to its effects on clotting parameters.

• Pregnant or breastfeeding women – Insufficient safety data. The theoretical risk of altered coagulation during pregnancy (a time when the body naturally increases clotting capacity to prepare for delivery) makes nattokinase inadvisable without medical guidance.

• People with active peptic ulcers or GI bleeding – The fibrinolytic effect could theoretically worsen GI bleeding.

• People with high blood pressure on medication – The additive blood pressure-lowering effect could cause hypotension. Monitoring is essential.

Drug Interactions

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Nattokinase Compared to Other Cardiovascular Supplements

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How does nattokinase stack up against other supplements commonly used for heart health?

Nattokinase vs. Omega-3 Fish Oil

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Omega-3 fatty acids have a much larger evidence base, including landmark trials like REDUCE-IT that demonstrated a 25% reduction in major cardiovascular events with high-dose EPA. Omega-3s primarily work through triglyceride reduction, anti-inflammatory effects, and membrane stabilization. Nattokinase works through fibrinolysis and blood viscosity reduction. These are complementary mechanisms, not competing ones. Taking both is reasonable for cardiovascular support, though be aware of the mild additive effect on bleeding time.

Nattokinase vs. CoQ10

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CoQ10 works through a completely different mechanism – mitochondrial energy production and antioxidant protection. The Q-SYMBIO trial showed significant benefits for heart failure patients. CoQ10 does not affect clotting or blood pressure in the same direct way nattokinase does. Again, these are complementary rather than overlapping.

Nattokinase vs. Berberine

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Berberine has stronger evidence for blood sugar control and LDL cholesterol reduction. If your primary concern is cholesterol or blood sugar management, berberine has a more robust evidence base. Nattokinase is stronger for fibrinolysis and blood pressure. For overall cardiovascular risk reduction, some practitioners recommend both.

Nattokinase vs. Aspirin

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Low-dose aspirin has been the standard antiplatelet agent for cardiovascular prevention for decades, though recent guidelines have narrowed the population for whom it is recommended due to bleeding risk. Aspirin works by irreversibly inhibiting cyclooxygenase in platelets, preventing thromboxane A2 production. Nattokinase works through fibrinolysis rather than platelet inhibition. They have different mechanisms, and combining them increases bleeding risk. Nattokinase should not be considered a replacement for aspirin in people for whom aspirin has been specifically prescribed.

Common Questions About Nattokinase

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What are the benefits of nattokinase?

Nattokinase has been studied for various potential health benefits. Research suggests it may support several aspects of health and wellness. Individual results can vary. The strength of evidence differs across different claimed benefits. More high-quality research is often needed. Always review the latest scientific literature and consult healthcare professionals about whether nattokinase is right for your health goals.

Is nattokinase safe?

Nattokinase is generally considered safe for most people when used as directed. However, individual responses can vary. Some people may experience mild side effects. It’s important to talk with a healthcare provider before using nattokinase, especially if you have existing health conditions, are pregnant or nursing, or take medications.

How does nattokinase work?

Nattokinase works through various biological mechanisms that researchers are still studying. Current evidence suggests it may interact with specific pathways in the body to produce its effects. Always consult with a healthcare provider before starting any new supplement or health regimen to ensure it’s appropriate for your individual needs.

Who should avoid nattokinase?

Nattokinase is a topic of ongoing research in health and nutrition. Current scientific evidence provides some insights, though more studies are often needed. Individual responses can vary significantly. For personalized advice about whether and how to use nattokinase, consult with a qualified healthcare provider who can consider your complete health history and current medications.

What are the signs nattokinase is working?

Nattokinase is a topic of ongoing research in health and nutrition. Current scientific evidence provides some insights, though more studies are often needed. Individual responses can vary significantly. For personalized advice about whether and how to use nattokinase, consult with a qualified healthcare provider who can consider your complete health history and current medications.

How long should I use nattokinase?

The time it takes for nattokinase to work varies by individual and depends on factors like dosage, consistency of use, and individual metabolism. Some people notice effects within days, while others may need several weeks. Research studies typically evaluate effects over weeks to months. Consistent use as directed is important for best results. Keep a journal to track your response.

Frequently Asked Questions

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Q: Does nattokinase survive stomach acid?

A: Yes. Nattokinase has demonstrated remarkable stability in the acidic environment of the stomach. Studies have shown that it retains its fibrinolytic activity after exposure to pH levels as low as 2.0, and it remains active in simulated gastric fluid. The enzyme is absorbed in the small intestine and has been detected in systemic circulation after oral administration, as confirmed by the Kurosawa et al. (2015) study showing measurable changes in coagulation parameters within hours of a single oral dose.

Q: Can vegetarians and vegans take nattokinase?

A: Yes. Although nattokinase is derived from soy fermentation, the manufacturing process does not involve animal products. The enzyme itself is produced by Bacillus subtilis bacteria during fermentation. Most nattokinase supplements are suitable for vegetarians, and many are vegan-friendly. Check the capsule material – some use gelatin (animal-derived) while others use vegetable cellulose (HPMC).

Q: Is nattokinase safe for people with soy allergies?

A: This is a nuanced question. Nattokinase is extracted from fermented soybeans, and some soy protein residues may remain in the final product. Highly purified formulations like NSK-SD undergo extensive processing that reduces soy allergen content, but they may not eliminate it entirely. If you have a severe soy allergy (anaphylaxis risk), it is safest to avoid nattokinase supplements. If you have a mild soy sensitivity, consult your allergist – some patients tolerate highly purified nattokinase without issues.

Q: Can I take nattokinase and aspirin together?

A: This combination increases bleeding risk because aspirin inhibits platelet aggregation while nattokinase enhances fibrinolysis – two different pathways that both favor reduced clotting. Some people do take both under medical supervision without problems, but it should not be done without your doctor’s knowledge. Your doctor may recommend choosing one or the other, or may approve the combination with appropriate monitoring.

Q: What is the difference between nattokinase and lumbrokinase?

A: Lumbrokinase is a fibrinolytic enzyme extracted from earthworms (Lumbricus rubellus). Like nattokinase, it has both direct fibrinolytic activity and the ability to activate plasminogen. Some practitioners prefer lumbrokinase for conditions involving more resistant clots, while nattokinase has a larger body of clinical research. Head-to-head comparative trials between the two enzymes are lacking.

Q: Will nattokinase show up on blood tests?

A: Nattokinase itself is not measured on standard blood panels. However, its effects may be visible in coagulation studies: you might see elevated D-dimer levels, increased fibrin degradation products, and potentially prolonged bleeding time. If you have blood work scheduled, inform your doctor that you take nattokinase so they can interpret results accurately.

Q: Can nattokinase help with varicose veins or spider veins?

A: There is limited direct evidence. The theoretical basis is that nattokinase’s fibrinolytic activity and blood viscosity reduction could improve venous circulation. Some practitioners recommend it for chronic venous insufficiency, but no randomized clinical trial has specifically tested nattokinase for varicose veins. Compression stockings, exercise, and vein-specific procedures have much stronger evidence for this condition.

Stacking Nattokinase: Complementary Supplements

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Nattokinase can be part of a comprehensive cardiovascular supplement regimen. Here are evidence-based combinations to consider:

Nattokinase + Omega-3 (EPA/DHA): Complementary mechanisms – nattokinase addresses fibrinolysis and blood viscosity while omega-3s target triglycerides, inflammation, and membrane function. This is one of the most physiologically rational cardiovascular stacks. See our omega-3 guide for dosing details.

Nattokinase + CoQ10: CoQ10 supports mitochondrial function in heart muscle and has blood pressure-lowering effects of its own. The Q-SYMBIO trial demonstrated significant benefits for heart failure. See our CoQ10 guide for comprehensive coverage.

Nattokinase + Magnesium: Magnesium supports healthy blood pressure, vascular tone, and cardiac rhythm. Most Americans are deficient. Combining magnesium with nattokinase addresses multiple cardiovascular risk factors simultaneously.

Nattokinase + Vitamin D: Vitamin D deficiency is associated with increased cardiovascular risk, impaired endothelial function, and elevated blood pressure. Correcting deficiency alongside nattokinase supplementation addresses two independent risk factors. See our vitamin D guide for dosing recommendations.

Nattokinase + Red Yeast Rice: The 2024 Liu et al. trial demonstrated that this specific combination produced the strongest lipid-lowering, blood pressure-lowering, and antithrombotic effects compared to either supplement alone. If lipid improvement is a goal alongside fibrinolytic support, this combination has direct clinical trial support.

Where to Buy Quality Supplements

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Based on the research discussed in this article, here are some high-quality options:

• Vitamin D Supplement
• Omega-3 Supplement
• Fish Oil Supplement
• Magnesium Supplement
• Protein Supplement

The Bottom Line

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Nattokinase is a genuinely interesting cardiovascular supplement with real pharmacological activity. It is not a cure-all, and the evidence is not as extensive as for some other cardiovascular interventions, but what exists is consistent and biologically plausible.

What the evidence clearly supports:

• Nattokinase produces measurable fibrinolytic and anticoagulant effects after a single oral dose
• It lowers blood pressure by approximately 3-5 mmHg systolic at 2,000 FU/day over 8 weeks
• It has a favorable safety profile when used as directed in appropriate populations
• It works through multiple complementary mechanisms that enhance the body’s own clot-dissolving capacity

What the evidence does not yet support:

• Nattokinase as a replacement for prescription anticoagulants – this is dangerous
• Significant lipid improvements at standard supplemental doses (2,000 FU/day)
• Prevention of atherosclerosis progression at standard doses (the NAPS trial was negative)
• Clinical benefits for Long COVID (in vitro data only, no RCTs yet)

What remains uncertain but promising:

• High-dose nattokinase (10,800 FU/day) for atherosclerosis and lipid management
• Nattokinase’s role in addressing Long COVID microclots
• Optimal dosing for different cardiovascular outcomes
• Long-term cardiovascular event reduction (no outcome trial exists)

For people with borderline blood pressure, elevated fibrinogen, poor circulation, or general cardiovascular risk factors, nattokinase at 2,000-4,000 FU/day is a reasonable addition to a comprehensive heart health strategy that includes diet, exercise, stress management, and medical care. It is not a substitute for any of those foundations, but it can complement them with a unique fibrinolytic mechanism that few other supplements provide.

As always, consult your healthcare provider before starting nattokinase, especially if you take any medications that affect blood clotting or blood pressure. This is a supplement with real pharmacological effects that deserves the same respect you would give any medication.

Related Articles

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• Omega-3 for Heart Health: How Much EPA and DHA Do You Actually Need? – Comprehensive analysis of fish oil clinical trials including REDUCE-IT, dosing guidance, and EPA vs DHA.
• CoQ10 Benefits, Dosage, and Side Effects: Complete Evidence-Based Guide – Everything about CoQ10 for heart failure, blood pressure, statin myopathy, and mitochondrial function.
• Best Supplements for High Cholesterol: What Cardiologists Recommend – Evidence-based options for managing cholesterol naturally, including red yeast rice and plant sterols.
• Best Supplements for High Blood Pressure: Natural Options Backed by Research – A full review of supplements that lower blood pressure, including magnesium, potassium, and beetroot.
• Berberine for Blood Sugar and Weight Loss: Complete Research Review – How berberine compares to metformin and its cardiovascular effects.

References

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1. Chen H, McGowan EM, Ren N, et al. Nattokinase: A Promising Alternative in Prevention and Treatment of Cardiovascular Diseases. Biomarker Insights. 2018;13:1177271918785130. doi:10.1177/1177271918785130. PubMed: https://pubmed.ncbi.nlm.nih.gov/30013308/ PMC: https://pmc.ncbi.nlm.nih.gov/articles/PMC6043915/

2. Kurosawa Y, Nirengi S, Homma T, et al. A single-dose of oral nattokinase potentiates thrombolysis and anti-coagulation profiles. Scientific Reports. 2015;5:11601. doi:10.1038/srep11601. PubMed: https://pubmed.ncbi.nlm.nih.gov/26109079/ PMC: https://pmc.ncbi.nlm.nih.gov/articles/PMC4479826/

3. Gallelli G, Di Mizio G, Palleria C, et al. Nattokinase Supplementation and Cardiovascular Risk Factors: A Systematic Review and Meta-Analysis of Randomized Controlled Trials. Reviews in Cardiovascular Medicine. 2024;24(8):234. doi:10.31083/j.rcm2408234. PubMed: https://pubmed.ncbi.nlm.nih.gov/39076715/ PMC: https://pmc.ncbi.nlm.nih.gov/articles/PMC11266782/

4. Kim JY, Gum SN, Paik JK, et al. Effects of nattokinase on blood pressure: a randomized, controlled trial. Hypertension Research. 2008;31(8):1583-1588. doi:10.1291/hypres.31.1583. PubMed: https://pubmed.ncbi.nlm.nih.gov/18971533/ PDF: https://www.nature.com/articles/hr2008203.pdf

5. Ren NN, Chen HJ, Li Y, et al. Nattokinase atherothrombotic prevention study: A randomized controlled trial. Clinical Hemorheology and Microcirculation. 2021;78(4):339-353. doi:10.3233/CH-211147. PubMed: https://pubmed.ncbi.nlm.nih.gov/33843667/

6. Ji H, Wang S, Zhang L, et al. Effective management of atherosclerosis progress and hyperlipidemia with nattokinase: A clinical study with 1,062 participants. Frontiers in Cardiovascular Medicine. 2022;9:964977. doi:10.3389/fcvm.2022.964977. PubMed: https://pubmed.ncbi.nlm.nih.gov/36072877/ PMC: https://pmc.ncbi.nlm.nih.gov/articles/PMC9441630/

7. Liu S, Li Y, Zeng X, et al. Lipid-lowering, antihypertensive, and antithrombotic effects of nattokinase combined with red yeast rice in patients with stable coronary artery disease: a randomized, double-blinded, placebo-controlled trial. Frontiers in Nutrition. 2024;11:1380727. doi:10.3389/fnut.2024.1380727. PMC: https://pmc.ncbi.nlm.nih.gov/articles/PMC11133624/

8. Chang YY, Liu JS, Lai SL, et al. Consequence of patient substitution of nattokinase for warfarin after aortic valve replacement with a mechanical prosthesis. Internal Medicine. 2014;53(20):2375-2377. doi:10.2169/internalmedicine.53.2786. PMC: https://pmc.ncbi.nlm.nih.gov/articles/PMC4264722/

9. Pretorius E, Kell DB, et al. Automated microscopic measurement of fibrinaloid microclots and their degradation by nattokinase, the main natto protease. bioRxiv. 2024. doi:10.1101/2024.04.06.588397. Full text: https://www.biorxiv.org/content/10.1101/2024.04.06.588397v1.full

10. Gallelli G, Cione E, Serra R, et al. Data Recorded in Real Life Support the Safety of Nattokinase in Patients with Vascular Diseases. Nutrients. 2021;13(6):2031. doi:10.3390/nu13062031. PMC: https://pmc.ncbi.nlm.nih.gov/articles/PMC8231931/

11. Research Progress of Nattokinase in Reducing Blood Lipid. Nutrients. 2025;17(11):1784. doi:10.3390/nu17111784. PubMed: https://pubmed.ncbi.nlm.nih.gov/40507053/ PMC: https://pmc.ncbi.nlm.nih.gov/articles/PMC12157000/

12. Ettehad D, Emdin CA, Kiran A, et al. Blood pressure lowering for prevention of cardiovascular disease and death: a systematic review and meta-analysis. Lancet. 2016;387(10022):957-967. doi:10.1016/S0140-6736(15)01225-8.