Vitamin K2

It was formerly given to premature infants, but due to inadvertent toxicity in the form of hemolytic anemia and jaundice,[failed verification] it is no longer used for this purpose.

[5] Vitamin K2, the main storage form in animals, has several subtypes, which differ in isoprenoid chain length.

Menaquinone-4 (also known as menatetrenone from its four isoprene residues) is the most common type of vitamin K2 in animal products since MK-4 is normally synthesized from vitamin K1 in certain animal tissues (arterial walls, pancreas, and testes) by replacement of the phytyl tail with an unsaturated geranylgeranyl tail containing four isoprene units, thus yielding menaquinone-4 which is water soluble in nature.

All K vitamins are similar in structure: they share a "quinone" ring, but differ in the length and degree of saturation of the carbon tail and the number of repeating isoprene units in the "side chain".

[1] Research suggests that vitamin K2 (Menaquinone 7, MK-7]) may reduce the rate and severity of night time leg cramps.

[citation needed] Vitamin K is absorbed along with dietary fat from the small intestine and transported by chylomicrons in the circulation.

[citation needed] Parts of the scientific literature, dating back to 1998, suggest that the AI values are based only on the hepatic requirements (i.e. related to the liver).

[15][16] This hypothesis is supported by the fact that the majority of the Western population exhibits a substantial fraction of undercarboxylated extra-hepatic proteins.

[citation needed] Thus, complete activation of coagulation factors is satisfied, but there does not seem to be enough vitamin K2 for the carboxylation of osteocalcin in bone and MGP in the vascular system.

According to Rebecca Rocchi et al., 2024, creating natto by using Bacillus subtilis to ferment boiled red lentils, chickpeas, or green peas produced greater amounts of MK-7 than creating natto by using Bacillus subtilis to ferment boiled soybeans, lupins, or brown beans.

[25] Food frequency questionnaire-derived estimates of relative intakes of vitamins K in one northern European country suggest that for that population, about 90% of total vitamin K intakes are provided by K1, about 7.5% by MK-5 through MK-9 and about 2.5% by MK-4;[citation needed] the intense smell and strong taste of nattō appear to make this soya food a less attractive source of K2 for Western tastes.

Supplement companies sell nattō extract reportedly standardized with regard to K2 content, in capsule form.

[citation needed] Notes: Recent studies found a clear association between long-term oral (or intravenous) anticoagulant treatment (OAC) and reduced bone quality due to reduction of active osteocalcin.

Also in humans on OAC treatment, two-fold more arterial calcification was found as compared to patients not receiving vitamin K antagonists.

[32][33] Among consequences of anticoagulant treatment: increased aortic wall stiffness, coronary insufficiency, ischemia, and even heart failure.

[38] One hydrogenated MK that sees relevant amounts of human consumption is MK-9(4H), found in cheese fermented by Propionibacterium freudenreichii.