Vitamin K is made up of several compounds that are essential to blood clot-ting. Vitamin K1, commonly called phylloquinone, is found in dietary sources, especially green leafy vegetables such as spinach and in animal tissue. Vitamin K2, called menaquinone, is synthesized in the intestine by bacteria and is also found in animal tissue. In addition, there is a synthetic vitamin K, called mena-dione. Vitamin K is destroyed by light and alkalies.
Vitamin K is absorbed like fats, mainly from the small intestine and slightly from the colon. Its absorption requires a normal flow of bile from theliver, and it is improved when there is fat in the diet.
Functions. Vitamin K is essential for the formation of prothrombin, which permits the proper clotting of the blood. It may be given to newborns immediately after birth because human milk contains little vitamin K and the intestines of newborns contain few bacteria. With insufficient vitamin K, newborns may be in danger of intracranial hemorrhage (bleeding within the head). Vitamin K may be given to patients who suffer from faulty fat absorption; to patients after extensive antibiotic therapy (ingestion of antibiotic drugs to combat infection) because these drugs destroy the bacteria in the intestines; as an antidote for an overdose of anticoagulant (blood thinner such as warfarin sometimes sold as Coumadin or Warnerin); or to treat cases of hemorrhage.
Sources. The best dietary sources of vitamin K are green leafy vegetables such as broccoli, cabbage, spinach, and kale. Dairy products, eggs, meats, fruits, and cereals also contain some vitamin K. Cow’s milk is a much better source of vitamin K than human milk. The synthesis of vitamin K by bacteriain the small intestine does not provide a sufficient supply by itself. It must be supplemented by dietary sources.
Requirements.Vitamin K is measured in micrograms. The AI for vita-min K is 120μg for men and 90μg for women. This is not increased during pregnancy or lactation. Infants up to 6 months should have 2.0μg a day. Those between 6 months and 1 year should receive 2.5μg a day. Vitamin K must be ingested daily. What is absorbed today will be utilized immediately with very little storage in the liver.
Hypervitaminosis.Ingestion of excessive amounts of synthetic vitaminK can be toxic and can cause a form of anemia.
Deficiency.The only major sign of a deficiency of vitamin K is defectiveblood coagulation. This increases clotting time, making the client more prone to hemorrhage. Human deficiency may be caused by faulty fat metabolism, antacids, antibiotic therapy, inadequate diet, or anticoagulants.