The vitamin K present in plant foods is called phylloquinone; while the form of the vitamin present in animal foods is called menaquinone. Both of these vitamins are absorbed from the diet and converted to an active form called dihydrovitamin K.
Vitamin K deficiency can be prevented by assuring that the diet contains foods such as green leafy vegetables (spinach, lettuce, broccoli), alfalfa, brussels sprouts and cabbage, which are good sources, containing about 8mg/kg. Cow's milk is also a good source of the vitamin, as are soy foods, egg yolks, and cauliflower. Soybean oil, canola oil and olive oil are good sources of the vitamin, while corn oil and peanut oil are very poor sources.
Vitamin K is a fat-soluble set of molecules that are required for the health of the human population. First discovered in the treatment of chicks with hemorrhagic diseases, vitamin K is vitally involved in the process of blood clotting. Three forms of biologically active vitamin K are known, they are menadione, phylloquinone, and menaquinone-7. Not only is vitamin K involved in the synthesis of clotting factors VII, IX, and X; it is also involved in the conversion of pre-prothrombin to prothrombin (the precursor to thrombin), which is important in fibrin blood clot formation.
The most common deficiency of vitamin K is at birth since vitamin K does not traverse well through the placenta, nor through breast milk. It is very common to give an intramuscular vitamin K shot to newborns for this reason.
When needed for the correction of prolonged bleeding due to over-anticoagulation with warfarin, oral vitamin K (1-5mg) was found to be as effective as IV administration, but had a slower onset of action. [Br J Haematol 2001;115(1): pp.145-149]
The US RDA recommends 1mcg of vitamin K per kilogram of weight per day. This means a person weighing 165 lbs (75 kilos) should ingest 75mcg of vitamin K daily. The RDA for vitamin K is 80mcg for adult males, 65mcg for adult females, and 5mcg for newborn infants.
People on any drug that is intended to change the blood clotting time, like Coumadin, should contact their physician before taking large amounts of vitamin K.
The U.S. RDA is 65mg.
Based on its ability to help blood clot normally, vitamin K has been proposed as a treatment for excessive menstrual bleeding and is beneficial for some women. Although bleeding time and prothrombin levels in women with menorrhagia are typically normal, the use of vitamin K (often in the form of chlorophyll) does have limited research support. Green leafy vegetables and other sources of vitamin K should be eaten freely.
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