Vitamin K2 in the MK-7 form (menaquinone-7) is one of the forms of vitamin K, produced by the same bacteria we use to ferment our natto in Zielona Góra. Here I have gathered where the name vitamin K came from, how MK-7 differs chemically from other menaquinones and where to look for it in the diet.
⚠️ 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.
In brief. The key facts about vitamin K2 MK-7
- Vitamin K2 MK-7 (menaquinone-7) is a form of vitamin K formed, among other ways, during fermentation, particularly by the bacterium Bacillus subtilis natto.
- Vitamin K contributes to normal blood clotting and to the maintenance of normal bones: these are the only two health claims authorised in the European Union for this vitamin (Regulation (EU) 432/2012).
- The name “vitamin K” comes from the Danish word “koagulation”, meaning coagulation: that is what its discoverer called it.
- The number in the abbreviation MK-7 refers to seven isoprene units in the side chain of the molecule, more than in the shorter MK-4.
- The richest natural source of MK-7 is natto, the product of soy fermentation.
Where the letter K in the vitamin’s name came from
Danish biochemist Henrik Dam discovered vitamin K in 1929 while studying cholesterol metabolism in chickens fed a fat-free diet. He noticed their tendency to bleed and isolated the compound responsible for normal blood clotting. He published his first results in a German scientific journal, naming the newly discovered substance “Koagulationsvitamin”. The abbreviation of that word, the letter K, was adopted internationally, even though the English word “coagulation” begins with the letter C. In 1943, Dam was awarded the Nobel Prize in Physiology or Medicine, together with Edward Doisy, who determined the chemical structure of the vitamin.
How MK-7 differs from other menaquinones
Vitamin K2 is a collective name for a group of compounds called menaquinones, abbreviated MK-n, where the number n indicates the length of the isoprene chain in the molecule. MK-4 has four such units, while MK-7, present in natto, has seven. The longer chain increases the lipophilicity of the molecule, which research describes as a longer circulation time of MK-7 in the blood compared with MK-4 (Schurgers et al., 2007). This is a description of the chemical structure and pharmacokinetics, not a claim of stronger action. Those looking for a full comparison of both forms will find it in a separate article Vitamin K2 MK-7 vs MK-4.
How MK-7 forms in our natto
MK-7 is produced during the fermentation of soy by the bacterium Bacillus subtilis natto, the same one we use to produce our natto in Zielona Góra. Fermentation lasts from several to several dozen hours, and the bacteria produce, among other things, vitamin K2 in the MK-7 form and the characteristic mucilaginous coating of the beans. That is why natto remains one of the richest natural sources of this form of vitamin K.
| Product | K2 content (µg/100 g, approximate) |
|---|---|
| Natto (fermented soy) | approx. 1000 |
| Gouda / edam cheese | 70 to 80 |
| Egg yolks | approx. 30 |
| Kefir, plain yoghurt | small amounts |
Vitamin K2 MK-7 in our dried natto
Fresh natto contains MK-7 in its natural, original form, and our dried natto with vitamin K2 MK-7 and D3 is a convenient tablet for daily use, produced in Zielona Góra from certified organic soy.
See dried natto with K2 MK-7 and D3 in the shop
Safety and precautions
Natto and supplements with vitamin K2 MK-7 are safe for most healthy people, but given the role of vitamin K in blood clotting, caution is advisable in certain situations.
This applies above all to people taking anticoagulant medicines from the vitamin K antagonist group (for example warfarin or acenocoumarol): consuming products rich in vitamin K, including natto, may affect how these medicines work and therefore requires consultation with a treating doctor. Caution is also advisable during pregnancy and breastfeeding, and when starting new supplementation while taking regular medication. Natto contains soy, so it is not suitable for people with an allergy to this allergen. A dietary supplement or any food product does not replace a varied diet and a healthy lifestyle.
Summary
Vitamin K2 MK-7 is a menaquinone with seven isoprene units in the side chain, whose name traces back to the Danish word “koagulation” and Henrik Dam’s discovery of 1929. Vitamin K contributes to normal blood clotting and to the maintenance of normal bones, and MK-7 belongs to its better-absorbed forms. The richest natural source of MK-7 is natto, the product of the fermentation of soy by the bacterium Bacillus subtilis natto, the same one we use in Zielona Góra.
FAQ
What is vitamin K2 MK-7?
It is a natural form of vitamin K2 (menaquinone-7), formed, among other ways, during the fermentation of soy by the bacterium Bacillus subtilis natto. It belongs to the better-absorbed forms of vitamin K.
Which health claims about vitamin K are authorised?
Two, authorised in the European Union: vitamin K contributes to normal blood clotting and to the maintenance of normal bones (Regulation (EU) 432/2012).
How does MK-7 differ from MK-4?
The number in the name indicates the length of the isoprene chain: MK-4 has four units, MK-7 has seven. The longer chain of MK-7 is associated with a longer circulation time in the blood than in the case of MK-4.
Where is there the most vitamin K2 MK-7?
The richest natural source is natto. Smaller amounts are found in aged cheeses and other fermented products.
Can everyone take vitamin K2?
People taking anticoagulant medicines from the vitamin K antagonist group should consult their doctor about consuming products rich in vitamin K.
Sources
- EFSA Panel, Scientific Opinion on the substantiation of health claims related to vitamin K, EFSA Journal, 2009.
- Schurgers L.J. et al., Vitamin K-containing dietary supplements: comparison of synthetic vitamin K1 and natto-derived menaquinone-7, Blood, 2007.
- Regulation (EC) No 1924/2006 and Regulation (EU) No 432/2012.
- EU Register of Nutrition and Health Claims (European Commission).
Legal and medical note. This article is educational and does not replace the advice of a doctor or pharmacist. Vitamin K has two authorised health claims in the European Union, relating to blood clotting and bones, and we do not attribute any others to it. A dietary supplement is not a medicine and does not replace a varied diet. Full information is on the Legal and medical information page.
