Vitamin K is one of four fat-soluble vitamins needed to maintain good health. Vitamin K supports blood clotting and may help protect your bone health. Vitamin K is available in a number of common foods, so most people do not need vitamin K supplementation. While you only need small amounts of vitamin K, it is of great value to your body.
Function
Vitamin K helps your blood coagulate. If you are cut or wounded, the coagulating, or clotting, ability of your blood prevents you from bleeding to death. Some evidence indicates that vitamin K plays a role in bone metabolism and can help protect against osteoporosis. A review of the literature on vitamin K's impact on bone health published in "Nutrition and Clinical Practice" in Octboer 2007 noted that studies and trials consistently support the relationship between vitamin K intake and improved bone mineral density and reduced risk of fracture.
Dosage
Because vitamin K can be stored in the liver and fatty tissues, you lose it much more slowly than you do water-soluble vitamins such as B and C vitamins. However, the body has the ability to store only a little vitamin K, so it is important to obtain it regularly from your diet. The Institute of Medicine recommends that adult women consume 90 micrograms of vitamin K daily and adult men consume 120 micrograms. One cup of raw spinach contains 145 micrograms of vitamin K.
Food Sources
Vitamin K is found primarily in dark, leafy greens. Kale, spinach, collard greens, parsley, Swiss chard, Brussels sprouts, cabbage and broccoli are common sources. Cooking these greens does not diminish their stores of vitamin K. Vitamin K deficiency is rare, but supplements are available. Deficiency is characterized by easy bruising and bleeding.
Considerations
If you are on prescription blood thinners, talk to your doctor about your vitamin K intake. Too much vitamin K can affect the way in which the drugs work. If you consume a lot of vitamin A, it may interfere with your ability to absorb vitamin K. If you are hoping to elicit bone benefits from vitamin K, you may need more than the 90 to 120 micrograms recommended daily. Speak to your doctor before purposefully increasing your intake, however.
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