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How Vitamin K Works

Foods That Contain Vitamin K
Vitamin K should be an important dietary elements, but where do you find vitamin K? It can be found in a number of foods, including some types of produce and beverages.

The best food sources of vitamin K are green leafy vegetables such as cabbage, turnip greens, broccoli, lettuce, and spinach. Green tea is another good source with one cup giving you your daily requirement of this nutrient. 

Broccoli is a great source of vitamin K.
©2007 Publications International, Ltd.
Green vegetables such as broccoli are great sources of vitamin K

Beef liver is another good source; chicken liver, pork liver, milk, and eggs contain smaller amounts of the vitamin. Liver, however, may also contain environmental toxins. Other sources, such as green tea, are better choices.

Not all of the vitamin K we get comes from the foods we eat. About one-third of our vitamin K comes from the bacteria living in our digestive tracts, which produce this vitamin as a by-product of their own metabolism. It used to be thought that intestinal bacteria produced about one-half of our vitamin K needs, but current findings indicate this was an overestimation.

Here is a chart you can use to find foods rich in vitamin K:

  Quantity  Vitamin K (mg)
Turnip greens
   2/3 cup        650
Lettuce    1/4 head
Cabbage    2/3 cup
Liver, beef
   3 ounces        110
Broccoli    1/2 cup        100
Spinach    1/2 cup
Asparagus    2/3 cup
Liver, pork
   3 ounces
Peas    2/3 cup
Ham    3 ounces

Dietary Requirements
For a long time, we didn't know enough about vitamin K to establish requirements. The first recommendation for the vitamin wasn't established until the 1989 edition of the RDAs.

The requirement varies by age; for men, it ranges from 75 to 120 mg as age increases from 11 to over 50 years. For women, the range is from 75 to 90 mg. A typical well-balanced diet in the United States supplies 300 to 500 mg of vitamin K -- more than enough to meet average dietary needs.

However, not every person meets the basic vitamin K requirements. In the next section, we'll discuss how even some healthy eaters with the best of intentions can become vitamin K deficient.

In addition to vitamin K, some other vitamins you might want to learn more about include:
  • Vitamin A is the vitamin found in carrots that improves eyesight. Learn more about this key vitamin in How Vitamin A Works.
  • Vitamin B3, also called niacin, assists other substances in the conversion of protein, carbohydrate and fat into energy. Learn more in How Vitamin B3 Works.
  • How Vitamin C Works will show you how this vitamin can strengthen your immune system.
  • Discovered only about 60 years ago, Biotin assists in several metabolic reactions. Learn more about it in How Biotin Works.
  • Vitamin B12 has a a chemical structure much more complex than that of any other vitamin. Learn about this vitamin How Vitamin B12 Works.
  • To learn about the many vitamins in our diet, how much you should be eating, and where to find them, go to our general Vitamins page.
  • Find the best prices on vitamin K supplements.
This information is solely for informational purposes. IT IS NOT INTENDED TO PROVIDE MEDICAL ADVICE. Neither the Editors of Consumer Guide (R), Publications International, Ltd., the author nor publisher take responsibility for any possible consequences from any treatment, procedure, exercise, dietary modification, action or application of medication which results from reading or following the information contained in this information. The publication of this information does not constitute the practice of medicine, and this information does not replace the advice of your physician or other health care provider. Before undertaking any course of treatment, the reader must seek the advice of their physician or other health care provider.