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Vitamin K ; Vitamin K 1 (Phylloquinone) ; Vitamin K 2 (Menaquinone) ; Vitamin K 3 (Menadione)

Proposed Uses: Osteoporosis; Treating Medication-induced Vitamin K Deficiency; Menorrhagia (Heavy Menstruation); Nausea

Vitamin K plays a major role in the body's blood clotting system. There are three forms of vitamin K: K 1 (phylloquinone), found in plants; K 2 (menaquinone), produced by bacteria in your intestines; and K 3 (menadione), a synthetic form.
Vitamin K is used medically to reverse the effects of "blood-thinning" drugs such as warfarin (Coumadin). Growing evidence suggests that it may also be helpful for osteoporosis.

Requirements/Sources
Vitamin K is an essential nutrient, but you need only a tiny amount of it.

Vitamin K (in the form of K 1) is found in green leafy vegetables. Kale and turnip greens are the best food sources, providing about 10 times the daily adult requirement in a single serving. Spinach, broccoli, lettuce, and cabbage are very rich sources as well, and you can get perfectly respectable amounts of vitamin K in such common foods as oats, green peas, whole wheat, and green beans, as well as watercress and asparagus.

Vitamin K (in the form of K 2) is also manufactured by bacteria in the intestines, and is a major source of vitamin K. Long-term use of antibiotics can cause a vitamin K deficiency by killing these bacteria. However, this effect seems to be significant only in people who are deficient in vitamin K to begin with.

Pregnant and postmenopausal women are also sometimes deficient in this vitamin.  In addition, children born to women taking anticonvulsants while pregnant may be significantly deficient in vitamin K, causing them to have bleeding problems and facial bone abnormalities.  Vitamin K supplementation during pregnancy may be helpful for preventing this.

The blood-thinning drug warfarin (Coumadin) works by antagonizing the effects of vitamin K. Conversely, vitamin K supplements, or intake of foods containing high levels of vitamin K, block the action of this medication and can be used as an antidote.

Cephalosporins and possibly other antibiotics may also interfere with vitamin K–dependent blood clotting. However, this interaction seems to be significant only in people who have vitamin K–poor diets.

People with disorders of the digestive tract, such as chronic diarrhea, celiac sprue, ulcerative colitis, or Crohn's disease, may become deficient in vitamin K. Alcoholism can also lead to vitamin K deficiency.

Therapeutic Dosages
In the study of osteoporosis described below, vitamin K was taken at the high dose of 1 g daily, more than ten times the necessary nutritional intake.

Therapeutic Uses
Growing evidence suggests that vitamin K should be added to the list of nutrients helpful for preventing osteoporosis.

Based on its ability to help blood clot normally, vitamin K has been proposed as a treatment for excessive menstrual bleeding.

Vitamin K has also been recommended for nausea, although there is as yet no meaningful evidence that it really works.

Preliminary evidence suggests that vitamin K supplementation may help prevent liver cancer.  Very high doses of intravenous vitamin K have also been used to treat advanced liver cancer, with, perhaps, marginal benefits.

Safety Issues
Vitamin K is quite safe at the recommended therapeutic dosages.
Note: Vitamin K directly counters the effects of the anticoagulant warfarin (Coumadin). If you are taking warfarin, you should not take vitamin K  without doctor supervision.

Newborns are commonly given vitamin K 1 injections to prevent bleeding problems. Although some have suggested that this practice may increase the risk of cancer, enormous observational studies have found no such connection.

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