chapter  6
27 Pages

Absorption, Storage, and Metabolism of Vitamin K

WithJohn W. Suttie

Absorption of phylloquinone from the intestine is via the lymphatic system and is therefore decreased in individuals with biliary insufficiency or various malabsorption syndromes. The distribution of vitamin K in various body organs of the rat was first studied with radioactive forms of the vitamin by using both massive and more physiological amounts of phylloquinone. The finding that a significant portion of dietary phylloquinone is subjected to side-chain cleavage to generate menadione is a very important advance in understanding the overall process of vitamin K metabolism. The substantial available literature dealing with the response of various markers of vitamin K status to alterations in vitamin K intake have seldom addressed the question of bioavailability of the vitamin. Substantial amounts of vitamin K are present in the human gut in the form of long-chain menaquinones. Limited information regarding the subcellular distribution of vitamin K within various tissues is available.