Dietary Reference Intake For Vitamin K

Vitamin K is a fat-soluble vitamin that is actually comprised of three related compounds, two of which are found in nature. Phylloquinone, or vitamin K-1, is the form that was first discovered in foods. Menaquinone, or vitamin K-2, is produced by bacteria in your intestine. A third form of vitamin K, K-3 or menadione, is synthesized in the laboratory and used for medical purposes. Like other fat-soluble vitamins -- A, D and E -- some vitamin K can be stored in your tissues.

Function

Phylloquinone was discovered in Denmark and labeled vitamin K when its role in "koagulation" was identified, according to nutritionist Elson Haas, M.D. Vitamin K is required for the synthesis of several proteins in your bloodstream called "clotting factors." Clotting factors are produced in your liver, and four of them are not fully functional until they are converted to their active forms by a vitamin-K dependent enzyme.

Sources

Vitamin K is found in both plant and animal foods. Alfalfa, kelp, polyunsaturated plant oils, such as safflower oil, dark leafy greens and most other green plants are good sources. Fish liver oils, liver, milk, yogurt and egg yolks are good animal sources of vitamin K. The bacteria in your intestine manufacture vitamin K in the form of menaquinone. Antibiotic therapy can reduce your ability to manufacture intestinal vitamin K.

Deficiency

Since vitamin K is fat-soluble, fat malabsorption can lead to vitamin K deficiency. Extremely poor intake of vitamin K-containing foods can also cause deficiency. A study published in April 2011 in "Nutrition" demonstrated that inflammatory bowel disease, such as Crohn's disease and ulcerative colitis, prevents adequate absorption of vitamin K. Treatment with the drug warfarin creates a relative deficiency of vitamin K by preventing its recycling after it participates in clotting factor synthesis. Bleeding is the usual manifestation of vitamin K deficiency.

Dietary Reference Intake

The Food and Nutrition Board at the Institute of Medicine has set dietary intake guidelines for vitamin K. On a daily basis, the DRI for infants 0 to 6 months is 2 micrograms; for ages 6 to 12 months, it's 2.5 micrograms; for children 1 to 3 years, it's 30 micrograms; for 4 to 8 years, it's 55 micrograms; for children 9 to 13 years, it's 60 micrograms; for adolescents 14 to 18 years, it's 75 micrograms; for males and females 19 years and older, it's 90 micrograms. If you take warfarin, you should avoid vitamin K supplements and limit your consumption of vitamin K-containing foods as recommended by your doctor..