Vitamin K derives its name from the German word ‘koagulation’. It is a fat-soluble vitamin important for the functioning of various proteins necessary for blood clotting. The term coagulation refers to the process of blood clot.
Vitamin K occurs in two natural forms. These are named vitamins K1 and K2, both derivatives of quinone.
Vitamin K functions primarily as a cofactor for an enzyme that carboxlates and catalyzes the amino acid and glutamic acid which finally converts to gamma-carboxyglutamic acid. The important
vitamin K-dependent proteins are coagulation proteins, anticoagulation proteins like proteins C, S and Z and a few others including bone proteins osteocalcin and matrix-Gla protein. These proteins need vitamin K to be biologically active.
Some people have the risk of forming blood clots which could prevent the flow of blood in the arteries of the lungs, brain and the heart causing heart attack or stroke. Though vitamin K is a fat-soluble vitamin, the body stores very little and that too gets depleted very quickly if not supplement by regular diet. Since the body does not store much of the vitamin K, it gets recycled by the body through a process called
vitamin K cycle. The vitamin K cycle permits a small amount of vitamin K to act in the in the gamma-carboxylation of proteins thereby reducing the dietary need. Oral anticoagulants or warfarin blocks the recycling of vitamin K by preventing two important reactions and creating a functional K deficiency. Large intake of vitamin K both in food and as supplements can guard the anticoagulant effect of vitamin K antagonists. Therefore, patients are issued a warning against taking large quantities of vitamin K in their diets.
Green leafy vegetables, cauliflower and liver are good sources of vitamin K. The main source of
vitamin K however, is the bacterial synthesis in the large intestine. The fetus receives its vitamin K from the mother.
Vitamin K deficiency causes impaired blood clotting with symptoms like bruising, bleeding gums, nose bleeds and blood in stools or even heavy menstrual bleeding. Vitamin K deficiency can prove fatal in infants leading to life-threatening bleeding in the skull. In adults, however,
vitamin K deficiency is rare mainly because it can be found in their daily diet. It is also conserved by the vitamin K cycle. People who suffer from vitamin K deficiency are those who consume vitamin K antagonist anticoagulant drugs.
Individuals with disorders of fat malabsorption are at a risk of vitamin K deficiency. Newborn babies who are breastfed are deficient in
vitamin K compared to formula fed babies. This is because the intestines of new born babies are not ready to synthesize menaquinones with bacteria. It has been researched that vitamin-K dependent proteins play a significant role in bone maintenance.
Heavy doses of vitamin A and vitamin E are said to antagonize
vitamin K. While tocopherol quinone, a form of vitamin E may block vitamin K dependent carboxlyase enzymes, Vitamin A on the other hand interferes with the absorption of vitamin K.
