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Vitamin K

Definition

Vitamin K is a fat-soluble vitamin that plays an important role in blood clotting. The body can store fat-soluble vitamins in fatty tissue.

Alternative Names

Vitamin K deficiency; Deficiency - vitamin K

Function

Vitamin K is known as the clotting vitamin, because without it blood would not clot. Some studies indicate that it helps in maintaining strong bones in the elderly.

Food Sources

Vitamin K is found in cabbage, cauliflower, spinach and other green leafy vegetables, cereals, soybeans, and other vegetables. Vitamin K is also made by the bacteria that line the gastrointestinal tract.

Side Effects

Vitamin K deficiency is very rare. It occurs when the body can't properly absorb the vitamin from the intestinal tract. Vitamin K deficiency can also occur after long-term treatment with antibiotics.

Individuals with vitamin K deficiency are usually more likely to have bruising and bleeding.

Recommendations

Specific recommendations depend on age, gender, and other factors (such as pregnancy). The best way to get the daily requirement of essential vitamins is to eat a balanced diet that contains a variety of foods from the food guide pyramid.

The Food and Nutrition Board at the Institute of Medicine recommends the following dietary intake for vitamin K:

Infants

  • 0 - 6 months: 2.0 micrograms per day (mcg/day)
  • 7 - 12 months: 2.5 mcg/day

Children

  • 1 - 3 years: 30 mcg/day
  • 4 - 8 years: 55 mcg/day
  • 9 - 13 years: 60 mcg/day

Adolescents and Adults

  • Males and females age 14 - 18: 75 mcg/day
  • Males and females age 19 and older: 90 mcg/day

If you take warfarin (a blood thinner), you should know that vitamin K or foods containing vitamin K can affect how the drug works. Ask your health care provider how much vitamin K or vitamin K-containing foods you should consume.

References

Rakel D, ed. Integrative Medicine. 2nd ed. Philadelphia, Pa: Saunders Elsevier; 2007.

Hamrick I, Counts SH. Vitamin and mineral supplements. Wellness and Prevention. December 2008:35(4);729-747.

Goldman L, Ausiello D, eds. Cecil Medicine. 23rd ed. Philadelphia, Pa: Saunders Elsevier; 2007.

Institute of Medicine. Food and Nutrition Board. Dietary Reference Intakes for Vitamin A, Vitamin K, Arsenic, Boron, Chromium, Copper, Iodine,Iron, Manganese, Molybdenum, Nickel, Silicon, Vanadium, and Zinc. National Academy Press, Washington, DC, 2001.

Review Date: 3/7/2009
Reviewed By: Linda Vorvick, MD, Family Physician, Seattle Site Coordinator, Lecturer, Pathophysiology, MEDEX Northwest Division of Physician Assistant Studies, University of Washington School of Medicine. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.
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