Nattokinase: The Fibrinolytic Enzyme From Ancient Japan and What the Research Actually Says

Nattokinase is a proteolytic enzyme derived from natto — a traditional Japanese fermented soybean food — that has been studied for decades for its role in supporting circulatory and cardiovascular wellness. Unlike many trending supplements with limited scientific backing, nattokinase has a well-documented discovery history and a growing body of clinical research examining its fibrinolytic properties. Here's what the science says — and what to look for if you're considering nattokinase as part of your daily wellness routine.

From Ancient Japan to Modern Research: The Origin of Nattokinase

Natto has been consumed in Japan for more than a thousand years, long revered in traditional culture as a food that supports circulation and heart health. The scientific story, however, began in 1987, when Dr. Hiroyuki Sumi — a researcher at the University of Chicago Medical School — placed a sample of natto onto an artificial blood clot in a petri dish and observed that the clot began dissolving within 18 hours [1]. The reaction was faster than any of the conventional thrombolytic agents Sumi had been studying at the time.

That observation launched a formal scientific investigation. Sumi and his colleagues isolated and characterized the specific enzyme responsible — naming it nattokinase — and published their findings the same year in the journal Experientia [1]. Nattokinase is produced not by the soybean itself, but by the bacterium Bacillus subtilis var. natto during the fermentation process. Importantly, it is the only soy-based food known to naturally contain this enzyme, and its concentration in natto is uniquely high.

Since Dr. Sumi's initial discovery, researchers in Japan, South Korea, China, and the United States have published extensively on nattokinase's pharmacological properties — making it one of the more thoroughly studied natural enzyme compounds in cardiovascular research [2].

Understanding the Fibrinolytic System

To understand why nattokinase has attracted sustained research interest, it helps to understand the role of fibrin in the body.

Fibrin is an insoluble protein that forms the structural backbone of blood clots. When the coagulation cascade is triggered — by injury, inflammation, or other stimuli — a protein called fibrinogen is converted into fibrin, which polymerizes into a mesh that traps blood cells and helps stop bleeding. This process is essential and life-preserving in the right context.

The body also has its own built-in mechanism for dissolving fibrin: a process called fibrinolysis, carried out primarily by the enzyme plasmin. Plasmin is activated from an inactive precursor (plasminogen) by tissue plasminogen activator (t-PA). In healthy individuals, the coagulation and fibrinolytic systems are in balance. When fibrinolytic activity is reduced or coagulation is excessive, fibrin can accumulate in ways that affect circulatory function.

This is where nattokinase enters the picture. Research has identified multiple mechanisms through which nattokinase supports the fibrinolytic system, all working at the biochemical level to help maintain the balance between clot formation and clot resolution [2, 3].

How Nattokinase Works: Five Mechanisms

Nattokinase is classified as a serine protease — specifically a member of the subtilisin family — with a molecular weight of approximately 28 kDa and 275 amino acid residues [2]. It is not a single-mechanism compound. Research has identified at least five distinct pathways through which it may exert its effects:

1. Direct Fibrin Degradation: Nattokinase directly cleaves fibrin crosslinks, breaking down the protein mesh that forms the structural core of blood clots. This is the mechanism first observed in Sumi's original 1987 experiments — and one of the most well-replicated findings in the nattokinase literature [1, 2].

2. Activation of Endogenous t-PA: Beyond direct fibrinolysis, nattokinase has been shown to stimulate the release of tissue plasminogen activator (t-PA) from vascular endothelial cells — essentially activating the body's own fibrinolytic enzyme system. This amplification effect means nattokinase does not act in isolation but works alongside the body's existing regulatory mechanisms [2, 3].

3. Inhibition of PAI-1: Plasminogen activator inhibitor type 1 (PAI-1) is an endogenous molecule that suppresses fibrinolytic activity by inactivating t-PA. Nattokinase has been demonstrated to cleave and inactivate PAI-1, thereby supporting the body's capacity for fibrin breakdown [3].†

4. Antiplatelet Activity: Research suggests nattokinase may support healthy platelet function by modulating thromboxane formation and platelet aggregation pathways — an area of ongoing investigation in cardiovascular wellness research.†

5. Fibrinogen Reduction: Several clinical studies have reported that nattokinase supplementation may support healthy fibrinogen levels already within the normal range, which is relevant because fibrinogen is the upstream precursor protein in the clotting cascade [2].†

What Is a "Fibrinolytic Unit" (FU)?

If you've been researching nattokinase supplements, you've likely encountered dosing expressed in FU — Fibrinolytic Units. This is the standardized measurement of enzyme activity used for nattokinase, and it's a more meaningful number than milligrams alone.

FU measures how much fibrin the enzyme can degrade under standardized laboratory conditions in a set amount of time. A higher FU count means higher enzymatic potency — not just more bulk weight of nattokinase. Two products may contain the same number of milligrams yet have very different actual fibrinolytic activity depending on the quality and concentration of the enzyme used.

The most commonly referenced doses in clinical research have clustered around 2,000–4,000 FU in earlier studies, with more recent work — and current consumer interest — moving toward 10,800 FU as a higher-potency benchmark. Therexa Nattokinase provides exactly 10,800 FU per serving (540 mg), delivering the level of enzyme activity that matches the upper end of what research has examined.

Why Enteric Coating Is a Critical Factor

Nattokinase is an enzyme — a protein — and like other proteins, it is susceptible to degradation in the acidic environment of the stomach (pH approximately 1–2 in a fasted state). Research has confirmed that nattokinase maintains its activity in a pH range of approximately 5–9, but activity drops sharply at lower pH levels [4]. Gastric acid and pepsin can inactivate a meaningful portion of nattokinase before it has the opportunity to reach the small intestine, where absorption occurs.

Enteric coating is a pH-sensitive coating applied to capsules specifically to address this problem. The coating resists dissolution in the acidic stomach environment and releases the enzyme in the more alkaline environment of the small intestine (pH approximately 6–7.5). From there, research — including intestinal transport studies in animal models — has confirmed that nattokinase can be absorbed across the intestinal tract and detected in the bloodstream [5].

Several clinical studies that have reported meaningful outcomes with nattokinase have used enteric-coated formulations [2]. Despite this, the majority of nattokinase products on the market — particularly at the 10,800 FU tier — do not include an enteric coating. This is a significant gap, as a product's FU count on the label reflects what was produced in the lab, not necessarily what remains intact after passing through the stomach.

Key Benefits Supported by Research

The research on nattokinase spans in vitro studies, animal models, and a growing number of human clinical trials. While research is ongoing and not all findings have been fully replicated, the consistent areas of focus include:

Cardiovascular and Circulatory Wellness: A comprehensive 2018 review published in Biomarker Insights examined the full scope of nattokinase's cardiovascular-relevant pharmacological effects, concluding that it represents a natural compound with several favorable properties for circulatory wellness — including fibrinolytic, antiplatelet, and blood pressure–related activities observed in preclinical and early human research [2].†

Healthy Fibrinolytic Activity: This is the most replicated area of nattokinase research. Multiple studies have documented that oral nattokinase supplementation can increase plasma fibrinolytic activity in healthy volunteers — supporting the body's own capacity to maintain healthy blood flow and breakdown of fibrin within the normal range [2, 3].†

Healthy Coagulation Factor Levels: Clinical research has found that regular nattokinase supplementation may support healthy levels of coagulation markers — including fibrinogen, factor VII, and factor VIII — already within normal ranges. In one published study, subjects using enteric-coated nattokinase for two months experienced reductions in these markers of approximately 7–19% [2].†

Arterial Health Support: Nattokinase has also been studied in the context of lipid metabolism and arterial tissue integrity, with a growing body of research examining its potential role in supporting healthy arterial function over time [2].†

What to Look for in a Nattokinase Supplement

With the growth in nattokinase's popularity, the market has become crowded — and quality varies considerably. Here's what matters most when evaluating a product:

FU count, not just milligrams: Always check the Fibrinolytic Unit count, not just the weight in milligrams. "Nattokinase 200 mg" means nothing without knowing the FU activity that corresponds to it. 10,800 FU represents the higher-potency tier that reflects current research interest.

Enteric coating: Given what is known about nattokinase's acid sensitivity, an enteric-coated capsule is a meaningful delivery advantage. It ensures the enzyme reaches the small intestine with its fibrinolytic activity intact — yet this feature is absent in the overwhelming majority of 10,800 FU products currently on the market.

Single-ingredient transparency: Nattokinase research has been conducted on nattokinase alone — not in combination with serrapeptase, bromelain, or multi-enzyme complexes. A clean, single-ingredient supplement panel makes it easier to attribute any response to the active compound and reflects how the most commonly cited research was designed.

Supply duration and value: Enzyme supplementation is most meaningful when maintained consistently. A 30-day supply requires a monthly purchase cadence that makes long-term adherence harder to maintain. 60-day supply bottles at comparable or lower per-serving cost represent a meaningfully better value proposition.

Quality signals: Third-party lab testing for enzyme activity and purity, GMP-registered facility production, and CoA availability are the baseline transparency markers that distinguish credible products from those with little accountability behind the label.

Therexa Nattokinase 10,800 FU: Formulated for Targeted Delivery

Therexa Nattokinase was designed to address each of the key gaps the research and market analysis point to. The formula delivers:

10,800 FU enzyme activity per serving (540 mg nattokinase) — the high-potency benchmark increasingly sought by informed consumers and referenced in emerging research.

Enteric-coated capsules — protecting enzyme activity through the acidic gastric environment and supporting targeted release in the small intestine, where absorption occurs.

120 capsules / 60-day supply — double the supply duration of most comparable 10,800 FU products at their standard bottle size, enabling consistent long-term supplementation.

Clean single-ingredient active panel — nattokinase is the only active ingredient listed in Supplement Facts; no fillers, combo enzymes, or secondary actives added.

Standalone nattokinase, not a multi-enzyme blend — matching the design of the studies most commonly referenced for nattokinase's fibrinolytic properties.

Every batch is produced in a GMP-registered facility and verified through independent, third-party lab testing for purity and potency. A Certificate of Analysis is available at therexa.co for full transparency. The formula is vegan-certified — no animal-derived capsule materials.

Important Notes Before You Start

Warfarin and anticoagulant medications: Nattokinase has fibrinolytic properties that may interact with blood-thinning medications, including warfarin (Coumadin), heparin, aspirin, and other antiplatelet drugs. If you are currently taking any anticoagulant or antiplatelet medication, do not take nattokinase without first consulting your healthcare provider. This is the most important safety consideration with this supplement.

Timing: Nattokinase is most commonly recommended on an empty stomach or between meals to minimize competition from food proteins. However, if you experience any digestive sensitivity, taking it with a small amount of food is a practical adjustment.

Consistency: Enzyme supplementation for circulatory wellness is intended as a long-term support strategy, not a one-time intervention. The clinical studies that have documented effects used supplementation durations of 4 weeks to several months — reinforcing the importance of consistent, uninterrupted use.

Not a replacement for medical care: Nattokinase is a dietary supplement, not a pharmaceutical agent. It should not replace prescribed medications or physician-guided treatment plans for cardiovascular conditions.

References

1. Sumi H, Hamada H, Tsushima H, Mihara H, Muraki H. A novel fibrinolytic enzyme (nattokinase) in the vegetable cheese Natto; a typical and popular soybean food in the Japanese diet. Experientia. 1987;43(10):1110–1111. doi:10.1007/BF01946480. PMID: 3678757.

2. Chen H, McGowan EM, Ren N, et al. Nattokinase: A Promising Alternative in Prevention and Treatment of Cardiovascular Diseases. Biomark Insights. 2018;13:1177271918785130. doi:10.1177/1177271918785130. PMID: 30013308. PMC: PMC6043915.

3. Urano T, Ihara H, Umemura K, et al. The profibrinolytic enzyme subtilisin NAT purified from Bacillus subtilis cleaves and inactivates plasminogen activator inhibitor type 1. J Biol Chem. 2001;276(27):24690–24696. doi:10.1074/jbc.M101751200. PMID: 11333271.

4. Lin HY, Tsai WC, Chen HC, et al. Stabilization and Target Delivery of Nattokinase Using Compression Coating. Drug Dev Ind Pharm. 2007;33(1):57–65. doi:10.1080/03639040600685932.

5. Fujita M, Hong K, Ito Y, Misawa S, Takeuchi N, Kariya K, Nishimuro S. Transport of nattokinase across the rat intestinal tract. Biol Pharm Bull. 1995;18(9):1194–1196. doi:10.1248/bpb.18.1194. PMID: 8520148.

6. Peng Y, Yang X, Zhang Y. Microbial fibrinolytic enzymes: an overview of source, production, properties, and thrombolytic activity in vivo. Appl Microbiol Biotechnol. 2005;69(2):126–132. doi:10.1007/s00253-005-0199-z. PMID: 16167153.

7. Wang C, Du M, Zheng D, et al. Purification and characterization of nattokinase from Bacillus subtilis natto B-12. J Agric Food Chem. 2009;57(20):9722–9729. doi:10.1021/jf902134p. PMID: 19803499.

Disclaimer

Structure/Function Claim Notice: The statements marked with † throughout this article have not been evaluated by the Food and Drug Administration (FDA). Therexa Nattokinase 10,800 FU is not intended to diagnose, treat, cure, or prevent any disease.

Not Medical Advice: The content in this article is provided for general informational and educational purposes only. It is not intended as, and should not be construed as, professional medical advice, diagnosis, or treatment. Always seek the guidance of your physician or another qualified healthcare professional before starting any new supplement regimen — particularly if you are pregnant, nursing, have a pre-existing medical condition, or are taking prescription medications.

Critical Drug Interaction Warning: Nattokinase has fibrinolytic properties that may affect the body's normal clotting mechanisms. It may potentiate the effects of blood-thinning medications including warfarin (Coumadin), heparin, aspirin, clopidogrel (Plavix), and other antiplatelet or anticoagulant agents. Individuals taking any such medications must consult a qualified healthcare provider before use. Nattokinase should be discontinued at least two weeks prior to any scheduled surgery.

Individual Results May Vary: Dietary supplements affect individuals differently. The benefits described in this article reflect findings from the referenced peer-reviewed research and are not a guarantee of specific outcomes for any individual.

Research Limitations: The scientific literature on nattokinase continues to evolve. While the referenced studies represent peer-reviewed findings, some areas of nattokinase research are still limited by small sample sizes or the need for larger randomized controlled trials. The studies cited do not constitute an endorsement of any specific product by the authors or their institutions.