Table of Contents
Key Takeaways:
- Nattokinase is an enzyme created by Bacillus subtilis var. natto bacteria during fermentation. The bacteria make the enzyme, not the soybean, which is why it can also be produced on chickpeas for a soy-free version with identical activity.
- Nattokinase’s discovery is credited to Dr. Hiroyuki Sumi, who observed a sample of natto dissolve an artificial blood clot in about 18 hours (Sumi et al., 1987).
- Potency is measured in fibrinolytic units (FU), not milligrams. FU describes how much fibrin-degrading activity a dose delivers under standardized lab conditions.
- The clinically studied supplement dose is 10,800 FU per day. Most commercial products provide around 2,000 FU, and natto is effectively the only meaningful food source of the enzyme.
Nattokinase is a fibrinolytic enzyme, meaning an enzyme that breaks down fibrin, the protein mesh that gives blood clots their structure. It’s produced by the bacterium Bacillus subtilis var. natto during the fermentation of natto, a traditional Japanese food, and it’s taken as a supplement to support healthy circulation and normal blood flow. Its potency is measured in fibrinolytic units (FU), a measure of enzyme activity rather than weight.
Where Does Nattokinase Come From?
Nattokinase was identified in natto, a fermented food eaten in Japan for over 1,000 years, and its discovery is credited to researcher Dr. Hiroyuki Sumi. In the experiment described in Sumi et al. 1987, he placed a sample of natto on an artificial blood clot in a petri dish and watched the clot dissolve within about 18 hours.
That single observation launched decades of research into nattokinase as a natural fibrinolytic agent. The name is a bit misleading: despite the "-kinase" suffix, nattokinase is a serine protease, an enzyme that cuts other proteins, not a kinase in the biochemical sense.
Natto itself remains a breakfast staple in parts of Japan. The food and the enzyme are related but not interchangeable, which trips up many first-time buyers.
How Is Nattokinase Produced?
Nattokinase is produced by the bacterium Bacillus subtilis var. natto during fermentation; the bacterium produces the enzyme, not the bean it grows on. Traditionally, the bacteria are cultured on steamed soybeans, which is how natto has been made for centuries.
Because the enzyme comes from the microbe rather than the substrate, manufacturers can ferment alternative legumes and get the same output. When Bacillus subtilis is cultured on chickpeas instead of soybeans, it produces the same nattokinase enzyme with identical fibrinolytic activity. That is how soy-free nattokinase is made, and it matters for the many people who avoid soy for allergy or dietary reasons.
For supplements, the enzyme is then isolated from the fermentation culture, standardized for activity, and tested. The purification step is also why most nattokinase supplements contain little or no vitamin K2, even though K2 occurs naturally alongside the enzyme in whole natto.
What Do Fibrinolytic Units (FU) Measure?
Fibrinolytic units (FU) measure how much fibrin-degrading activity a nattokinase dose delivers, not how many milligrams of powder it contains. Enzymes are catalysts, so what matters is activity: two products with the same milligram weight can have very different FU values depending on strain, production quality, and handling.
This is the single most useful number on a nattokinase label. Milligrams tell you how much material is in the capsule or scoop. FU tells you what that material can actually do, as measured against a standardized fibrin substrate in the lab.
It is also why "proprietary blend" labels are a red flag in this category. If a product does not state its FU per serving, there is no way to know whether it delivers a research-relevant dose or a trace amount.
How Do Supplement Doses Compare to Eating Natto?
The clinically studied dose of nattokinase is 10,800 FU per day, whereas most commercial supplements provide about 2,000 FU per serving. The largest clinical study to date (Chen et al., 2022; 1,062 participants over 12 months) used 10,800 FU daily, and a 3,600 FU arm in the same study was found to be ineffective. Dose matters because enzymatic effects are threshold-dependent: below a certain activity level, there is simply not enough fibrinolytic capacity to measure an effect.
Food is the other route, but it has practical limits. Natto is effectively the only meaningful dietary source of nattokinase, and its enzyme content varies from batch to batch because fermentation is a living process. Natto's strong smell, sticky texture, and acquired taste also keep it off most Western tables.
Two practical notes carried over from the research on the live page:
- Orally taken nattokinase survives digestion. Research published in Scientific Reports confirmed the enzyme is absorbed intact and retains fibrinolytic activity in the bloodstream (Kurosawa et al., 2015).
- The enzyme has a functional half-life of approximately 8 to 12 hours, which is consistent with the once-daily dosing used in most clinical trials.
For people who want the studied dose without eating natto daily, that’s the role a supplement like Toku Flow fills. A powder format makes the full 10,800 FU practical in a single serving, along with vitamin K2 (MK-7), which purification usually strips out.
Parting Thoughts
Nattokinase is best understood in three ways: it’s an enzyme produced by bacteria during fermentation, its potency is measured in FU rather than milligrams, and the studied dose (10,800 FU) is well above what most products and any realistic diet provide. Start with the FU number on the label, and if you want the mechanism in detail, the science article below picks up where this definition leaves off.
FAQs
What is the food natto?
Natto is a traditional Japanese food made by fermenting steamed soybeans with Bacillus subtilis var. natto bacteria, and it has been a dietary staple in Japan for over 1,000 years. The fermentation gives natto its characteristic sticky strands, strong aroma, and nutritional profile: nattokinase, vitamin K2, protein, and beneficial bacteria. It is most often eaten over rice at breakfast.
What beans have nattokinase?
No bean naturally contains nattokinase; the enzyme only appears when Bacillus subtilis var. natto bacteria ferment a legume. Soybeans are the traditional substrate because natto is a soybean food. The same bacteria cultured on chickpeas produce the same enzyme with identical fibrinolytic activity, which is the soy-free method Toku uses for Toku Flow.
What foods are highest in nattokinase?
Natto is effectively the only meaningful food source of nattokinase. Other fermented foods, such as miso, tempeh, or kimchi, use different microbes or processes and do not provide the enzyme in comparable amounts. If natto is not part of your diet, a standardized supplement is the practical way to get a defined FU dose.
What does nattokinase do in the body?
Nattokinase supports the body's normal fibrinolysis process, the routine breakdown and clearing of fibrin. It acts on fibrin directly and also supports the body's own plasmin system, the natural machinery for dissolving fibrin once a clot has done its job. Research shows the enzyme survives digestion, reaches the bloodstream in active form (Kurosawa et al., 2015), and remains active for roughly 8 to 12 hours per dose. Because it influences clotting-related pathways, anyone taking anticoagulant or antiplatelet medication should talk to their doctor before using it.
*The information provided in this article is for educational and informational purposes only and is not intended as health or medical advice. Always consult a physician or other qualified health provider regarding any questions you may have about a medical condition or health objectives. This content has not been evaluated by the Food and Drug Administration and is not intended to diagnose, treat, cure, or prevent any disease.
Sources:
- Sumi H, Hamada H, Tsushima H, et al. A novel fibrinolytic enzyme (nattokinase) in the vegetable cheese Natto. Experientia. 1987;43(10):1110-1111. https://link.springer.com/article/10.1007/BF01956052
- 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. https://www.nature.com/articles/srep11601
- Chen et al., 2022. Effective management of atherosclerosis progress and hyperlipidemia with nattokinase: A clinical study with 1,062 participants. https://www.frontiersin.org/journals/cardiovascular-medicine/articles/10.3389/fcvm.2022.964977/full
- 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. https://www.nature.com/articles/hr2008203
