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Vitamin K

Definition

Vitamin K is a fat-soluble vitamin.

Alternative Names

Phylloquinone; K1; Menaquinone; K2; Menadione; K3

Function

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

Food Sources

The best way to get the daily requirement of vitamin K is by eating food sources. Vitamin K is found in the following foods:

• Green leafy vegetables, such as kale, spinach, turnip greens, collards, Swiss chard, mustard greens, parsley, romaine, and green leaf lettuce
• Vegetables such as Brussels sprouts, broccoli, cauliflower, and cabbage
• Fish, liver, meat, eggs, and cereals (contain smaller amounts)

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.

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

If you take blood thinning drugs (such as anticoagulant/antiplatelet drugs), you may need to limit vitamin K foods. You should know that vitamin K or foods containing vitamin K can affect how these drugs work.

It is important for you to keep vitamin K levels in your blood about the same from day to day. Ask your health care provider how much vitamin K-containing foods you should eat.

Recommendations

The Recommended Dietary Allowance (RDA) for vitamins reflects how much of each vitamin most people should get each day.

• The RDA for vitamins may be used as goals for each person.
• How much of each vitamin you need depends on your age and gender.
• Other factors, such as pregnancy, breast-feeding, and illness may increase the amount you need.

The Food and Nutrition Board at the Institute of Medicine Recommended Intakes for Individuals - Adequate Intakes (AIs) 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

References

Escott-Stump S, ed. Nutrition and Diagnosis-Related Care. 8th ed. Philadelphia, Pa: Lippincott Williams & Wilkins; 2008.

Sarubin Fragaakis A, Thomson C. The Health Professional's Guide to Popular Dietary Supplements. 3rd ed. Chicago, IL: American Dietetic Association;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.

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.