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Vitamin K

By Shereen Jegtvig, About.com

Updated March 19, 2009

About.com Health's Disease and Condition content is reviewed by our Medical Review Board

Spinach

Spinach is a great source of vitamin K.

Photo © Florin Bleiceanu
Definition: Vitamin K is a member of the fat-soluble family of vitamins that also includes vitamin D, vitamin E and vitamin A. Vitamin K is important for normal blood clotting and may help to keep your bones strong as you age.

Vitamin K deficiency is rare, but may occur after long-term use of antibiotics. It is important to note that people who are taking blood thinners should consult with their doctors or pharmacists about vitamin K supplementation because taking extra vitamin K can reduce the effectiveness of blood thinners.

Daily Requirements

Males

1 to 3 years 30 mcg per day
4 to 8 years 55 mcg per day
9 to 13 years 60 mcg per day
14 to 18 years 75 mcg per day
19+ years 120 mcg per day

Females

1 to 3 years 30 mcg per day
4 to 8 years 55 mcg per day
9 to 13 years 60 mcg per day
14 to 18 years 75 mcg per day
19+ years 90 mcg per day

Vitamin K is found in dark green leafy vegetables, cabbage, cauliflower, broccoli, and soybeans. Vitamin K is also synthesized in your digestive tract by friendly bacteria.

Also Known As: Phylloquinone, menaquinone

Sources:

MedlinePlus. "Vitamin K." NIH. Updated 01/2007.

Food and Nutrition Board. "Dietary Reference Intakes." Institute of Medicine. Published 2004.
Vegetables Rich in Vitamin K
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