Metabolism of vitamin K

There are two principal forms of vitamin K: vitamin K1 (phylloquinone) is found in plant foods and vitamin K2 (menaquinone) is derived from animal and bacterial sources.

Vitamin K1, K2 and K3 (menadione) are essential nutrients associated with blood clotting and bone metabolism.

Vitamin K1 is fat soluble and requires bile salts for absorption in the upper gastrointestinal tract.

Vitamin K seems to play an indispensible role in the formation of normal amounts of prothrombin by the liver.

Prothrombin, in turn is a constituent of the blood essential to normal blood clotting. Deficiency in prothrombin results in an appreciable prolongation of the clotting time of the blood.

Vitamin K acts a factor in the final synthesis of proteins with modified amino acid residue.

This modified glutamic acid residue is found in the blood and along vessel walls, along with platelet-derived phospholipid, where it binds and facilitates the action of calcium, and is an integral part of the clotting process.

Many drugs impair vitamin K metabolism. Broad spectrum antibiotics destroy the colonic bacteria that produce vitamin K and can increase risk of deficiency.

Drugs which impair fat absorption aloes can reduce absorption of vitamin K.
Metabolism of vitamin K