Vitamin K

Vitamin K gets its name from the Scandinavian word koagulation, which means the same as its English counterpart, coagulation. In this case, the name is an indication of the function. Vitamin K is essential to the formation of precursors of thrombin, which is the active agent in the clotting of blood. Thrombin acts upon fibrinogen to form the fibrin blood clot. Vitamin K does not actually become part of the clot or the precursors of thrombin, though it is required for their synthesis in the liver.

A deficiency of vitamin K results in lowered levels of prothrombin and other precursors of thrombin, and, therefore, reduced coagulability of the blood and increased bleeding tendency. Recent research suggests that vitamin K is also necessary for other biochemical functions besides coagulation. Animal studies have shown it is required for proper bone mineralization.

Vitamin K deficiency is relatively rare because the vitamin is synthesized by intestinal bacteria. However, in newborns vitamin K deficiency is fairly common, if not the rule, since newborns have no intestinal bacteria. If the deficiency is severe enough, bleeding from the gastrointestinal tract, bloody stools, or bloody vomiting occur within the first week or so of life. Internal bleeding or bleeding from the umbilicus can follow. In adults, vitamin K deficiency can result in excess bleeding from wounds and blood in the urine and stools.

Nevertheless, deficiencies do exist. Many common factors can cause a vitamin K deficiency. Antibiotic therapy is the most common cause of a deficiency. The vitamin-producing bacteria in the gut are destroyed by antibiotics, thus removing the primary source of this vitamin.

Besides antibiotics, sulfa medications can lead to a vitamin K deficiency. Anticoagulant medications often work by interfering with vitamin K. And vitamin K deficiency hemorrhaging can occur in newborns born to epileptic mothers taking barbiturates or phenytoin. Since vitamin K is a fat-soluble vitamin, any medication or disorder which interferes with absorption of fat will impair vitamin K absorption. Some of these conditions are pancreatic dysfunction, sprue, celiac disease, steatorrhea, and ingestion of mineral oil.

Vitamin K is not destroyed by heat, but it is vulnerable to oxidation, acids, alkalies, and light.
Although there is no reported toxicity for natural vitamin K in adults, the vitamin is available in supplemental form only through a doctor's prescription.

Where is it found ?

The richest natural sources of vitamin K are the green leafy vegetables, such as cabbage, cauliflower, and spinach. Liver and soybeans are also good sources. Of course, the primary source is synthesis by bacteria in the intestine.

Who is likely to be deficient ?

A vitamin K deficiency, which causes uncontrolled bleeding, is rare, except in individuals with certain malabsorption diseases. All newborn infants receive vitamin K to prevent deficiencies that sometimes develop in breast-fed infants.

How much to take

Many physicians suggest 65 to 80 mcg per day, a level ,that can be achieved without supplementation by eating vegetables.

Side effects

Vitamin K interferes with the action of some prescription blood thinners. People taking these medications should never supplement vitamin K without consulting a physician. Phylloquinone-the natural vegetable form of vitamin K-has not been linked with any other side effects.
Vitamin K facilitates the effects of calcium in building bone and proper blood clotting.

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