Coumadin, known generically as warfarin, is a brand of medication used to prevent clots within your blood vessels. Blood clots can be very dangerous. If significant, they can lead to restriction of blood flow and death of affected tissues. Coumadin works by reducing the production of vitamin K within your liver, a fat-soluble vitamin responsible for the formation of blood clots. Several factors, including diet, influence the anti-coagulation ability of Coumadin. Therefore, you should have careful monitoring by your doctor while taking the drug.
Vitamin K Content
You should avoid foods rich in vitamin K while taking Coumadin, as it may counteract the anti-coagulant effects of the drug. In general, green leafy vegetables are the highest sources of vitamin K, with a ½-cup serving of kale possessing the highest content at 660 percent of the recommended daily value. Other foods rich in vitamin K include boiled spinach, collard greens, parsley, boiled turnip greens and boiled mustard greens. Foods possessing moderate amounts include brussels sprouts, broccoli, romaine lettuce and raw spinach.
Alternatively, a diet deficient in vitamin K may enhance the effects of Coumadin and is something you should also avoid. As a rule of thumb, the National Institute of Health recommends consuming no more than one ½-cup serving of food with a high content of vitamin K, equivalent to 200 percent or more of the daily value. The NIH also recommends no more than three ½-cup servings of foods with a moderately high content of vitamin K, equivalent to 60 to 199 percent of the daily value. The established daily value of vitamin K for adults is 80 micrograms.
Alcoholic Beverages
The consumption of three or more alcoholic beverages per day may also amplify the effects of Coumadin. Acute ingestion of alcohol increases the amount of Coumadin in the bloodstream, thereby increasing the risk of bleeding. Chronic alcohol consumption, on the other hand, decreases the amount of Coumadin and reduces its effectiveness. One serving of alcohol is equivalent to 12 oz. of beer, 5 oz. of wine or 1.5 oz. of hard liquor.
Olestra
Olestra is a synthetic fat substitute that contains several fat-soluble vitamins such as vitamin K. Carefully monitor your consumption of food products containing olestra, such as potato chips, and all foods with moderate to high amounts of vitamin K.
Dietary Supplements
A number of dietary supplements also interfere with the effectiveness of Coumadin, including black cohosh, dandelion, ginko biloba, green tea, licorice, nettle, poplar, St. John's wort and yarrow. Vitamin C and vitamin E may also increase bleeding when taken at dosages higher than 500 milligrams and 400 International Units, respectively. Multivitamins are typically low in vitamin K and therefore should not be a cause for concern as long as you take the vitamin regularly.
Warning
Call your physician if you experience mild bleeding that is not life threatening, such as bleeding of the gums or nose that stops after several minutes. Seek immediate medical attention for severe bleeding that does not cease after several minutes or if you vomit blood. These are signs that your Coumadin dosage is too high and in need of adjustment.
References
- New York University Medical Center; Managing Your Warfarin (Coumadin) Therapy: A Patient's Guide; March 2002
- National Institute of Health Drug-Nutrient Interaction Task Force; Coumadin and Vitamin K; December 2003
- "Alcohol Alert"; Alcohol-Medication Interactions; Dr. Charles S. Lieber; January 1995
- Ohio State University Medical Center; Diet and Warfarin (Coumadin); June 2009
