Natto is not only a traditional Japanese dish, but also a source of an enzyme called nattokinase, which is increasingly discussed in the context of fermented food. This article explains what nattokinase is, how it is produced and what the scientific literature says about it. It is educational in nature and does not make any claims about treating or preventing disease.
In brief
- Nattokinase forms naturally during the fermentation of soy by the bacterium Bacillus subtilis natto.
- It is an enzyme from the serine protease group, classified in the literature among fibrinolytic enzymes.
- In the European Union, nattokinase has no authorised health claim (Regulation (EC) 1924/2006).
- Clinical studies in humans are few and methodologically varied.
- Natto is a food, not a substitute for anticoagulant medicines.
What nattokinase in natto is
Nattokinase is a protein enzyme first described in 1987 by the Japanese researcher Hiroyuki Sumi. It forms during the fermentation of soy by the bacteria Bacillus subtilis natto and is a natural product of the activity of these microorganisms. In laboratory studies, its ability to break down fibrin, the protein that is the main structural component of blood clots, has been described.
The amount of nattokinase in natto depends on the quality of the soy and on the temperature and time of fermentation. In fresh natto the enzyme activity can range from several hundred to several thousand FU units per gram, which makes this product one of the richer natural sources of this enzyme.
What research says, and what is not yet known
The best documented mechanism of action of nattokinase under in vitro conditions (in a test tube) is the hydrolysis of fibrin. The literature also describes single studies in animal models and a few clinical studies in humans, including Kim et al. (2008), concerning blood pressure.
An important methodological note: results obtained in a test tube and in animals do not automatically translate into effects in humans after oral intake. Nattokinase is a large protein molecule, and the question of to what extent it reaches the bloodstream in active form after oral administration remains a matter of discussion in the literature. There is also a lack of large, independent clinical studies and of consensus on dosing. For these reasons, no specific health effect of nattokinase has been authorised in the EU.
Nattokinase and vitamin K2
Fresh natto naturally contains both nattokinase and vitamin K2 in the MK-7 form. Unlike nattokinase, vitamin K has two health claims authorised in the EU:
- vitamin K contributes to normal blood clotting,
- vitamin K contributes to the maintenance of normal bones (Regulation (EU) 432/2012).
Some nattokinase supplements are deliberately free of vitamin K2 in order to avoid interaction with anticoagulant medicines. Fresh natto, as a food, contains both substances.
For whom natto may not be advisable
Natto is a food that is safe for most healthy people. Caution is advised for:
- people taking anticoagulant medicines (warfarin, acenocoumarol), because of the vitamin K content,
- patients after surgery or with clotting disorders,
- pregnant and breastfeeding women,
- people with a soy allergy.
In these cases, including natto in the diet is worth consulting with a doctor.
Natto versus a nattokinase supplement
| Feature | Natto (food) | Nattokinase supplement |
|---|---|---|
| Source | Fermented soy | Extract from natto |
| Nattokinase content | Variable (several hundred to several thousand FU/g) | Standardised (e.g. 2000 FU/capsule) |
| Accompanying components | Vitamin K2, fibre, protein, live bacterial cultures | Usually no additional components |
| Status in the EU | Food | Food supplement, without authorised claims for nattokinase |
Natural natto provides a broader spectrum of components, while supplements focus on the enzyme itself.
Summary
Nattokinase is an example of a biologically active compound that forms during the traditional fermentation of soy. Its action has been described mainly in laboratory studies, and clinical data in humans remain limited. Fresh natto is a valuable food that can be part of a varied diet, not an alternative to pharmacological treatment.
FAQ
Is nattokinase a medicine?
No. In the EU it is a component of food or of a food supplement, without the status of a medicinal product and without an authorised health claim.
How much nattokinase does a portion of natto contain?
Depending on the fermentation conditions, from several hundred to several thousand FU units.
Is eating natto every day safe?
For most healthy people, yes. In Japan natto is eaten daily. Caution is advised with anticoagulant medicines.
Can nattokinase be combined with blood medicines?
The decision to combine any preparation with anticoagulant medicines should be made only after consulting a treating doctor.
For whom is natto not recommended?
For people with clotting disorders, pregnant women, and patients taking anticoagulant medicines without consulting a doctor.
Sources
- Sumi H. et al., A novel fibrinolytic enzyme (nattokinase) in the vegetable cheese Natto, Experientia, 1987.
- Kim J.Y. et al., Effects of nattokinase on blood pressure: a randomized, controlled trial, Hypertension Research, 2008.
- Regulation (EC) No 1924/2006 and Regulation (EU) No 432/2012.
- EU Register of Nutrition and Health Claims (European Commission).
We are a Polish producer of natto made from organic soy. Our content is based on scientific literature and a passion for fermented food.
Important note: The content of this article is for educational and informational purposes only. It does not replace professional medical advice, diagnosis or treatment. Natto is a food, not a medicine. Nattokinase has no authorised health claim in the EU. People taking anticoagulant medicines (e.g. warfarin, acenocoumarol) should consult their treating doctor about including natto in their diet, because of its high vitamin K content.
