Nattokinase is a powerful fibrinolytic enzyme extracted from natto, a traditional Japanese food made from fermented soybeans. For over 1,000 years, natto has been consumed in Japan as a heart-healthy food. Today, modern science has isolated nattokinase as the active compound responsible for natto's cardiovascular benefits, particularly its ability to dissolve blood clots and improve circulation.
Quick Facts
Reading time: 12 min
Evidence level: Research-backed
Target audience: US & European consumers
What Is Nattokinase?
Nattokinase is an enzyme produced by Bacillus subtilis natto during the fermentation of soybeans. It was discovered in 1980 by Dr. Hiroyuki Sumi, who found that it had potent fibrinolytic (clot-dissolving) activity.
Unlike prescription blood thinners that prevent clot formation, nattokinase actively breaks down fibrin, the protein mesh that forms blood clots. This makes it unique among natural cardiovascular supplements.
The enzyme is measured in fibrinolytic units (FU), with most clinical studies using 2,000-7,000 FU daily. The NSK-SD brand is the most clinically studied form and is considered the gold standard.
- Fibrinolytic enzyme from fermented soybeans (natto)
- Actively dissolves blood clots (fibrin breakdown)
- Measured in fibrinolytic units (FU)
- NSK-SD is the most clinically studied form
- 1000+ year history of safe consumption as natto
Cardiovascular and Circulation Benefits
Nattokinase's primary benefit is improving blood flow by breaking down fibrin and reducing blood viscosity. A 2024 meta-analysis in the Journal of Nutrition examined 15 clinical trials and found consistent reductions in blood pressure with nattokinase supplementation.
A landmark study found that 2,000 FU of nattokinase daily for 8 weeks reduced systolic blood pressure by an average of 5.5 mmHg and diastolic by 2.8 mmHg in hypertensive patients.
Beyond blood pressure, nattokinase reduces blood viscosity (thickness), improves microcirculation, and may help dissolve existing micro-clots. This makes it particularly valuable for people with poor circulation or elevated cardiovascular risk.
- Reduces systolic BP by 5-6 mmHg at 2000 FU daily
- Lowers diastolic BP by 2-3 mmHg
- Reduces blood viscosity and improves flow
- Breaks down fibrin (clot protein) safely
- Improves microcirculation throughout the body
Blood Clot Prevention and Safety
Nattokinase's clot-dissolving ability is its most clinically significant property. It works by converting plasminogen to plasmin, the body's natural clot-busting enzyme, and directly degrading fibrin.
Unlike pharmaceutical clot busters (like tPA), nattokinase works gradually over hours, making it safe for daily use. It does not cause excessive bleeding in healthy individuals at recommended doses.
However, nattokinase should NOT be combined with prescription blood thinners (warfarin, Eliquis, Xarelto, Plavix) without medical supervision, as the combination may increase bleeding risk. Always consult your doctor if you take any anticoagulant medications.
- Converts plasminogen to plasmin (natural clot buster)
- Degrades fibrin directly without excessive bleeding risk
- DO NOT combine with prescription blood thinners without doctor approval
- Stop 2 weeks before any surgery
- Not recommended for people with bleeding disorders
Dosage and How to Take Nattokinase
The standard dose used in most clinical studies is 2,000 FU (fibrinolytic units) daily, typically split into two doses of 1,000 FU each. For cardiovascular support, this dose is effective for blood pressure and circulation improvement.
Take nattokinase on an empty stomach (30 minutes before meals or 2 hours after) to prevent the enzyme from being used for protein digestion rather than systemic fibrinolysis.
Some practitioners recommend taking it at bedtime, as blood clot risk is highest during sleep when circulation slows. The effects are cumulative, with maximum benefits seen after 4-8 weeks of consistent use.
- Standard dose: 2,000 FU daily (split into 2 doses)
- Take on empty stomach for systemic absorption
- Best taken before meals or at bedtime
- Full effects take 4-8 weeks of consistent use
- Look for NSK-SD or Doctor's Best branded enzyme
Choosing the Best Nattokinase Supplement
The most important quality marker is the FU (fibrinolytic units) rating. Avoid products that list milligrams without FU, as this doesn't indicate enzyme activity. The clinically studied NSK-SD form is preferred.
Top brands include Doctor's Best Nattokinase (NSK-SD, 2,000 FU), NOW Foods Nattokinase, and Double Wood Supplements Nattokinase. All of these use the NSK-SD enzyme and clearly list FU content.
Avoid products that combine nattokinase with other blood-thinning ingredients like garlic extract, ginkgo, or fish oil in the same capsule, as this makes dosing less precise and increases bleeding risk.
- Always check FU (fibrinolytic units), not just mg
- NSK-SD is the most clinically studied form
- Avoid products with added blood thinners in same capsule
- Top brands: Doctor's Best, NOW Foods, Double Wood
- Store in a cool, dry place - heat degrades the enzyme
Important Safety Note
This information is for educational purposes only and is not medical advice. Always consult with a qualified healthcare provider before starting any supplement regimen.
The Bottom Line
Nattokinase is a powerful fibrinolytic enzyme extracted from natto, a traditional Japanese food made from fermented soybeans. For over 1,000 years, natto has been consumed in Japan as a heart-healthy Understanding the science behind these products is essential for making informed health decisions.
For more information, explore our related guides, check our FAQ page, or browse our supplement glossary.
Frequently Asked Questions
Is nattokinase safe to take daily?
Yes, nattokinase is safe for daily use at recommended doses (2,000 FU) for most healthy adults. However, do not take it if you are on prescription blood thinners, have a bleeding disorder, or are scheduled for surgery within 2 weeks. Always consult your doctor if you take any medications.
Can nattokinase replace blood thinners?
No. Nattokinase should not be used as a replacement for prescription anticoagulants (warfarin, Eliquis, Xarelto) without your doctor's supervision. It may complement conventional treatment, but never stop prescribed blood thinners on your own. Discuss with your cardiologist.
Does nattokinase have vitamin K2?
Pure nattokinase enzyme supplements do not contain significant vitamin K2. However, whole natto (the food) is rich in K2. If you want both, take nattokinase for circulation and a separate K2 supplement for bone/arterial health. Some combination products include both.
What time of day should I take nattokinase?
Take nattokinase on an empty stomach, either 30 minutes before meals or at bedtime. Many practitioners recommend bedtime dosing, as blood clot risk increases during sleep. Split the daily dose into two servings (morning and evening) for sustained fibrinolytic activity.