Jewish World Review Feb. 10, 2003 / 8 Adar I, 5763

Eating smart: Vitamin K And the coagulation factor

By Sheldon Margen and Dale A. Ogar | Vitamin K, like vitamins A, D and E, is a fat-soluble vitamin, which means it is metabolized along with fat in the body and is best taken with meals. But unlike those more familiar substances, not much Vitamin K is stored in your body fat. Fortunately, about 80 percent of the vitamin K you need is synthesized by bacteria that live in your intestinal tract.

Without vitamin K, your blood would not clot. The process by which this works is complex; basically, vitamin K acts as a catalyst that transforms anti-clotting proteins into clotting proteins when you suffer a cut or wound.

We have the Danes to thank for this discovery. Back in the 1930s, scientists in Copenhagen found out that chicks fed a fat-free diet suffered from bleeding problems. The researchers eventually discovered that a substance in alfalfa cured the condition. They named it vitamin K, for the Danish spelling of "koagulation.''

The recommended daily allowance for vitamin K is relatively modest, between 60 and 80 mcg, depending on one's age and gender. Deficiencies are extremely rare in healthy people. However, they can occur in those with certain mal-absorption syndromes or liver disease, or who are undergoing long-term antibiotic therapy. In addition, some infants do not have the necessary intestinal bacteria to manufacture vitamin K and may need supplementation for a period of time.

The biggest worry these days about vitamin K is for people who have circulatory or cardiovascular disease and are put on blood-thinning drugs like Coumadin or Warfarin. These drugs can interfere with the body's production of vitamin K; and in a serious injury, it may be difficult to stop the bleeding. However, physicians who prescribe such drugs generally monitor the vitamin K status of their patients.

In the normal course of events, healthy people would have a difficult time getting too much vitamin K. It is only really abundant in leafy green vegetables, such as broccoli and brussels sprouts. Other vegetables, fruits and some fats contain smaller amounts. It bears noting that vitamin K is difficult to measure in foods; thus, the USDA has developed a list of provisional values for a number of foods.

One misconception about vitamin K is that green tea is the richest food source for it, and that drinking green tea (which we have recommended for its other benefits) would be dangerous for people who must control vitamin K intake. However, this is only true if you eat the leaves, instead of brewing them into tea. While it is true that 8 ounces of dried tea leaves contain 1,700 mcg of vitamin K (a huge amount), 8 ounces of leaves would actually make hundreds of cups of brewed tea, which researchers at Tufts University have found contains almost no vitamin K at all.

Keep in mind that very high doses of vitamin E (probably above the levels we recommend) can interfere with vitamin K function; vitamin E not only serves as an antioxidant, but as a mild anticoagulant.

If you're taking any kind of supplements, inform your primary-care provider so that possible interactions and contraindications can be considered. Do not assume that self-prescribed, over-the counter drugs or supplements are completely without risk. This is most important to remember if you have a specific medical condition or are taking prescription medications. Always tell your doctor everything you are taking.

What should you do if your doctor tells you to watch your vitamin K intake? After years of eating more green vegetables because of the health-promoting substances they contain, it may be hard to eliminate those very foods from your diet and still get the benefit of their vitamins, minerals, fiber and antioxidants. Fortunately, Mother Nature has provided; most of the nutrients in broccoli are also available in other foods that may have a lower vitamin K content. Citrus fruits can fill in the vitamin C content. Many of the carotenoids can be found in other dark-green or otherwise brightly colored vegetables and fruits. Some of the so-called cancer-fighting compounds in broccoli may be harder to replace, but for individuals with known cardiovascular and atherosclerotic disease, this is a reasonable trade-off.

"The Coumadin Cookbook: A Complete Guide to Healthy Meals when Taking Coumadin,'' by Rene Desmarais, M.D., Gregory Golden and Gail Beynon, was written to help individuals on anticoagulant drugs. The book is available from the publisher: Marsh Publishing: PO Box 1597, Salisbury MD 21802-1597. Sample recipes are posted online at, which also lists foods low in vitamin K and offers suggestions for calculating the amount of vitamin K you do ingest.

Sheldon Margen, M.D., is a professor of public health at the University of California at Berkeley. Dale A. Ogar is managing editor of the University of California at Berkeley "Wellness Letter.'' They are the authors of "The Simply Healthy Lowfat Cookbook,'' "The Wellness Lowfat Cookbook'' and "The Wellness Encyclopedia of Food and Nutrition.'' Comment by clicking here.


© 2003, Distributed by TMS