Vitamin K is a major nutrient that plays a role in blood clotting, among other functions. Vitamin K is a fat-soluble vitamin. Such vitamins are absorbed into the body dissolved in lipids (fatty or oily substances). They are stored in the body in the liver and in fat tissues.
Three forms of vitamin K are known. One form, called phylloquinone or K1, is produced by plants. Another form, called menaquinone or K2, is produced by bacteria living naturally in the intestines . Synthetic vitamin K is called menadione, or K3. All three forms serve the same purpose in the body.
Food sources of vitamin K include green, leafy vegetables such as kale and spinach . However, it is difficult to accurately measure the amount of vitamin K present in foods.
Deficiency.
People who lack a particular vitamin can develop a vitamin deficiency disease. Because vitamin K is synthesized by bacteria in the colon , part of the large intestine, deficiency is rare. It sometimes occurs in people with disorders that impair the absorption of fats or with liver disease. Inadequate levels of vitamin K result in the formation of nonfunctional blood clotting proteins, leading to hemorrhage (bleeding).
Function.
Vitamin K functions as a cofactor for an enzyme called carboxylase. In the body, enzymes serve as catalysts, substances that speed up chemical reactions . Cofactors are substances that serve to activate or enable enzymes. Carboxylase is involved in the production of proteins that bind calcium . Such proteins include those that promote blood clotting and others involved in bone formation.
Anticoagulant medications, such as warfarin, work in opposition to vitamin K. These medications are used to prevent blood clots in people who are at risk of stroke . Patients who take these medications should establish a consistent intake of vitamin K. Doctors can then adjust the drug dosage to balance the vitamin K intake.
Vitamin K toxicity (poisoning) rarely occurs in adults. It is occasionally seen when a high dose of the synthetic form is given to newborn babies.
History.
The Danish chemist Henrik Dam observed a disease in newborn chicks whose symptoms, bleeding and an increased blood clotting time, were caused by the lack of a particular nutrient. Dam called this substance vitamin K, short for koagulations-vitamin. Coagulation (Dutch, koagulation) is another word for clotting. In 1929, Dam and others managed to isolate a fat-soluble vitamin present in the green leaves of cabbage, tomatoes, and soybeans, as well as animal liver. In 1939, the American chemist Edward Doisy isolated and synthesized vitamin K3.
