Warfarin can be a life-saving medication when administered properly, decreasing the activity of vitamin K and thereby slowing the process by which blood clots form in the body. Patients taking this medication must exercise caution in their dietary practices and monitor their intake of foods high in vitamin K. Patients should discuss any other medications and supplements they are taking with their physician before taking Warfarin.
Warfarin
Warfarin, the active ingredient in Coumadin, is a powerful blood-thinning medication typically prescribed in cases in which there is considerable risk of blood clot formation. The individual already might have a clot in or near the heart that could trigger a heart attack, stroke or organ damage. Warfarin also is prescribed when there is a clot in the lungs, as in pulmonary embolism, or elsewhere in the body, as with venous thrombosis. Those with heart rhythm abnormalities and/or mechanical artificial heart valves also can have a tendency to form blood clots.
Vitamin K and Warfarin
Warfarin works by decreasing the activity of vitamin K, which plays a key role in the chemical reactions that lead to the formation of a blood clot. Therefore, the amount of vitamin K consumed in the diet must stay relatively constant for Warfarin to work properly. An increased intake of vitamin K foods can decrease the blood thinning action of Warfarin, and a decreased intake of vitamin K can lead to excessive thinning of the blood and a greater risk of uncontrolled bleeding.
Foods High in Vitamin K
Green, leafy vegetables -- such as the boiled forms of kale, collards, spinach, turnip greens, mustard greens and Swiss chard -- and raw parsley contain the highest levels of vitamin K per serving. A single half-cup serving of any of these vegetables can contain anywhere from 260 percent to 660 percent of your daily recommended vitamin K. Raw romaine lettuce, green leaf lettuce, spinach, turnip greens, broccoli, endive lettuce and boiled Brussels sprouts have moderately high concentrations of vitamin K. For individuals taking Warfarin, the National Institutes of Health recommends no more than one serving per day of foods high in vitamin K and no more than three servings per day of those moderately high in vitamin K.
Other Nutrient and Supplement Considerations
Soybean oil, red cabbage, asparagus and iceberg lettuce have often been singled out as high in vitamin K, but they contain far less than the above-mentioned foods. The NIH advises that these foods can be consumed as desired, but other foods and products like alcoholic beverages, cranberries, various herbal supplements, vitamin E and certain antibiotics have been found to affect the action of Warfarin. The Food and Drug Administration advises those taking Warfarin to avoid consuming cranberry products and alcoholic beverages completely and to clear all dietary supplements and other medications with their physicians.
Warning
While taking warfarin can be life-saving, the potential side effects also are quite dangerous and there is increased risk for internal bleeding if the drug is taken incorrectly. Bleeding issues become more likely in people over 75 and those taking other blood-thinning medications. It is very important to discuss all potential side effects and warning signs with your doctor once this medication is prescribed.
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