Menaquinone-7

Menaquinone-7, usually abbreviated MK-7, is one of the menaquinones, the family of fat-soluble molecules that together make up vitamin K2 ^[1][4]. All menaquinones are built around the same naphthoquinone ring but differ in the length of an attached isoprenoid tail; in the MK-n shorthand the number states how many isoprenoid units that tail contains, so MK-7 carries seven of them ^[1][4]. The longer-chain menaquinones, a group that includes MK-7 along with MK-8 and MK-9, are typical of fermented foods, whereas the short MK-4 is the form that animal tissue can generate from vitamin K1 ^[1].

The outstanding dietary source of MK-7 is natto, a traditional Japanese dish of soybeans fermented with Bacillus subtilis, in which it accounts for most of the vitamin K2 content ^[1][2]. Lesser amounts are found in some aged cheeses and other fermented products, all of which reflect the capacity of bacteria to build menaquinones ^[1]. This bacterial origin also underlies modern manufacturing, since commercial MK-7 destined for supplements is generally obtained by controlled fermentation with Bacillus strains rather than by chemical synthesis ^[6]. Interest in the compound grew as researchers recognized that the naturally occurring long-chain menaquinones behave differently in the body from the more familiar vitamin K1 ^[4].

Like all K vitamins, MK-7 serves as a cofactor for gamma-glutamyl carboxylase, the enzyme that activates a set of vitamin K-dependent proteins by adding carboxyl groups to their glutamate residues ^[4]. Among these proteins are the clotting factors made in the liver, osteocalcin in bone, and matrix Gla protein in cartilage and blood-vessel walls, the last of which helps restrain the calcification of soft tissue ^[2][4]. On the strength of these roles, MK-7 has been studied for its potential to support bone mineralization and cardiovascular health, and comparative work shows that it produces more complete carboxylation of osteocalcin than vitamin K1 does ^[2]. Even so, whether supplementing specifically with vitamin K2 offers a clear advantage over vitamin K1 remains unsettled, and the clinical evidence is often described as inconclusive ^[1].

A defining feature of MK-7 is its pharmacokinetics. Human studies find that after absorption it persists in the circulation with a much longer half-life than either vitamin K1 or MK-4, giving steadier blood levels and allowing it to accumulate over days of repeated intake ^[2][3]. In one comparison, dietary MK-4 did not measurably raise serum vitamin K levels at nutritional intakes, whereas MK-7 reliably did, a finding frequently cited as a reason to prefer the long-chain form in supplements ^[3]. MK-7 is marketed as an over-the-counter dietary supplement rather than a prescription drug, and it is sold both as isolated menaquinone and as natto-derived extract in capsules and tablets ^[2]. Because even modest amounts of MK-7 can interfere with the action of vitamin K antagonist anticoagulants such as warfarin, its use is generally discouraged in people taking those medicines ^[5].

MK-7 is very safe and well tolerated with no established toxicity at normal doses. The big exception is that it can interfere with warfarin and similar vitamin-K-antagonist blood thinners, so those users must not take it without medical guidance. Natto-derived MK-7 may matter for soy allergy depending on the product.