Natto and Vitamin K2 MK7

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⚠️ Are you taking anticoagulant medication (for example acenocoumarol or warfarin)? Natto is one of the richest natural sources of vitamin K, which may affect how these medicines work. Consult your diet and supplements with a doctor. See the important legal and medical information.

Natto is one of the richest natural sources of vitamin K, mainly in the form of menaquinone-7 (K2 MK-7). Vitamin K contributes to normal blood clotting and to the maintenance of normal bones (Regulation (EU) 432/2012). On this page we have gathered knowledge about the scientific basis of these claims, the bioavailability of MK-7 and the differences between the forms of vitamin K.

Why natto is one of the richest sources of vitamin K in the MK-7 form

Natural natto has several features that set it apart from other sources of vitamin K:

  • High content: fresh natto contains about 1970 µg of vitamin K per 100 g, predominantly in the K2 MK-7 form.
  • The K2 MK-7 form: the long-chain form of menaquinone-7 has a long half-life in the body, which is confirmed by scientific research[1].
  • Natural origin: vitamin K2 MK-7 is formed during the fermentation of soy by Bacillus subtilis Natto bacteria. It is naturally accompanied by other compounds present in fermented soy, including the enzyme nattokinase.

Why the MK-7 form matters

Vitamin K2 occurs in several forms (menaquinones from MK-4 to MK-13). MK-7 is the long-chain form with a long half-life, which means it stays in the body longer than the short-chain MK-4 and provides a more stable level with once-daily consumption. A full comparison of both forms is in the article Vitamin K2 MK-7 vs MK-4, differences between forms.

Vitamin K and the maintenance of normal bones

Vitamin K contributes to the maintenance of normal bones (Regulation (EU) 432/2012). This is the only authorised health claim linking vitamin K with bone tissue.

What the science says. In the scientific literature, research on vitamin K2 MK-7 and bone tissue focuses on the activity of osteocalcin, a calcium-binding protein in the bone matrix. Vitamin K is one of the cofactors needed to activate osteocalcin[2]. A three-year study from 2013 showed an effect of low doses of MK-7 on markers of bone-structure maintenance in postmenopausal women[2].

In line with food law, here we describe the scientific context. The only authorised health information about vitamin K and bones remains the wording from Regulation (EU) 432/2012 (above).

Vitamin K and vitamin D in the diet

Vitamin K and vitamin D are nutrients whose EFSA health claims complement one another in the context of the skeletal system and calcium metabolism.

NutrientAuthorised EFSA wordings (selected)
Vitamin K
  • Vitamin K contributes to normal blood clotting.
  • Vitamin K contributes to the maintenance of normal bones.
Vitamin D
  • Vitamin D contributes to the normal absorption and utilisation of calcium and phosphorus.
  • Vitamin D contributes to the maintenance of normal bones.

All the wordings above were authorised by Regulation (EU) 432/2012.

In the scientific literature, research is published on the metabolic interactions between these vitamins and bone mineralisation[3].

Frequently asked questions

How does K2 MK-7 differ from vitamin K1?
K1 (phylloquinone) comes mainly from green vegetables, while K2 (menaquinones, including MK-7) is produced primarily through bacterial fermentation. These are two distinct groups within vitamin K.
Is natto a good source of vitamin K2?
Natto is the richest known natural dietary source of vitamin K2 in the MK-7 form. Content can vary between batches, which is natural for a fermented product.
Are K2 MK-7 and nattokinase the same thing?
No. Vitamin K2 MK-7 is a vitamin, and nattokinase is an enzyme produced during the fermentation of natto. These are two different substances. Nattokinase has no authorised health claim in the EU.

In-depth knowledge about vitamin K2

We have gathered extended knowledge about vitamin K2 on our topical site k2mk7.pl.

📚 Scientific sources and bibliography

The content presented is based on peer-reviewed scientific publications:

  1. Bioavailability of MK-7 from natto. Sato T. et al. (2012). Nutrition Journal. DOI: 10.1186/1475-2891-11-93
  2. MK-7 and bone tissue. Knapen M.H.J. et al. (2013). Osteoporosis International. DOI: 10.1007/s00198-013-2325-6
  3. Interactions of vitamins D and K. van Ballegooijen A.J. et al. (2017). International Journal of Endocrinology. DOI: 10.1155/2017/7454376

Marek Kołodziejski, M.Sc. Eng., founder of the Natto.pl manufactory

About the author

Marek Kołodziejski, M.Sc. Eng., founder and creator of the Natto.pl manufactory, an engineer leading research and development work on the fermentation and drying of natto.

Author of the low-temperature convection drying technology that protects vitamin K2 MK-7, nattokinase and live bacterial cultures.

Winner of the Economic Award of the Marshal of the Lubuskie Region (2024, Innovative Micro-enterprise category) for research work and the production of fresh and dried natto as a functional food.

Legal and medical note. This page is educational and does not replace the advice of a doctor or pharmacist. The health claims cited regarding vitamin K and vitamin D are authorised by Regulation (EU) 432/2012 and refer to these nutrients, not to a specific product. A food supplement is not a medicine and does not replace a varied diet. Full information is on the Legal and medical information page.