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Vitamin K2

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Common name: Vitamin K2



Vitamin K2 (menatetrenone) effectively prevents fractures and sustains lumbar bone mineral density in osteoporosis.

The role of vitamin K2 in the development of hepatocellular carcinoma in women with viral cirrhosis has been explored in a paper published in the July 21st issue of the Journal of the American Medical Association.

The role of vitamin K2, or menaquinone, in controlling cell growth has been identified in previous studies.

Japanese scientists were therefore interested to discover if vitamin K2 has preventative effects on the development of hepatocellular carcinoma in women with viral cirrhosis of the liver.

Dr Daiki Habu and colleagues from Osaka City University, Osaka, Japan studied 40 women diagnosed with viral liver cirrhosis who were admitted to a university hospital between 1996 and 1998.

The women were randomly assigned to either the treatment group, who received 45 mg/d of vitamin K2 (n = 21), or the control group, who did not receive the vitamin treatment.

Both groups received symptomatic therapy to treat ascites, if necessary, and dietary advice.

The scientists originally set out to assess the long-term effects of vitamin K2 on bone loss in women with viral liver cirrhosis.

However, since study participants also satisfied criteria required for examination of the effects of such treatment on the development of hepatocellular carcinoma, they focused their attention on this.

Hepatocellular carcinoma was detected in 2 of the 21 women given vitamin K2 and 9 of the 19 women in the control group.

The cumulative proportion of patients with hepatocellular carcinoma was smaller in the treatment group, while on univariate analysis, the risk ratio for the development of hepatocellular carcinoma in the treatment group compared with the control group was 0.20.

On multivariate analysis with adjustment for age, alanine aminotransferase activity, serum albumin, total bilirubin, platelet count, -fetoprotein, and history of treatment with interferon alfa, the risk ratio for the development of hepatocellular carcinoma in patients given vitamin K2 was 0.13.

The researchers therefore conclude that there is a possible role for vitamin K2 in the prevention of hepatocellular carcinoma in women with viral cirrhosis.

Vitamin K is known as the anti-hemorrhagic vitamin that is necessary for the synthesis of four of the 13 cofactors required for the normal coagulation of blood.

There are a number of compounds possessing vitamin K activity. Two naturally occurring forms of vitamin K exist: vitamin K1 and K2.

Vitamin K is also necessary for the synthesis of four other proteins involved in hemostasis: proteins C, S, Z and M.

Vitamin K1 and K2 are found in green plants and in microorganisms, respectively.

There are also synthetic forms of vitamin K, one of which is menadione.

Vitamin K1 (phylloquinone or phytylmenaquinone) and K2 (menaquinone or multiprenyl-metaquinone) are fat soluble and stable during cooking.

Vitamin K1 is not stable under sunlight.

Synthetic vitamin K (e.g. menadione) is water-soluble and destroyed to a great degree during cooking.

Natural vitamin K (K1 and K2) requires bile and pancreatic juice for absorption in the small intestine.

Vitamin K2 is synthesized by microflora in the small and large intestine. However, the degree of contribution to vitamin K status in the body and absorption is not well understood.

Menadione is converted to vitamin K2 in the body.

Synthesis of osteocalcin that promotes mineral deposition in bone is dependent on vitamin K.

Vitamin K: Dietary Reference Intake

0 to 6 months: 2.0 mg/day
7-12 months: 2.5 mg/day

1 to 3 years: 30 mg/day
4 to 8 years: 35 mg/day

9 to 13 years: 60 mg/day
14 to 18 years: 75 mg/day
19+ years: 120 mg/day

9 to 13 years: 60mg/day
14 to 18 years:75mg/day
19+ years : 95mg/day

Values are Adequate Intake (AI). Tolerable upper intake levels (UL)are not determinable due to lack of data of adverse effects and concern with regard to lack of ability to handle excess amounts.


Menaquinone (vitamin K2) biosynthesis.