Vitamin K comprises a family of compounds known as quinones which include phylloquinone from plants and menaquinone from animal sources. Phylloquinone is the most biologically active form. Menaquinones are also synthesized by bacteria in the colon and absorbed, contributing about 10 percent of total vitamin-K needs.
Vitamin-K absorption depends on normal consumption and digestion of dietary fat. It is primarily stored in the liver.
The critical role of vitamin K in blood clotting, was first noted in 1929, by the Danish researcher Henrik Dam who named it ‘vitamin K’ for "Coagulation."
Vitamin K helps in the activation of seven blood-clotting-factor proteins that participate in a series of reactions to form a clot that eventually stops the flow of blood.
Vitamin K also participates in the activation of bone proteins, which greatly enhances their calcium-binding properties. Low levels of circulating vitamin K are associated with low bone-mineral density. Thus, adequate intake of vitamin K may help in protection against hip fractures.