Coumadin, also known as warfarin, is an anticoagulant medication, or blood thinner. According to Drugs.com, Coumadin is prescribed to reduce the formation of blood clots in those individuals at risk for heart attack, stroke, or blood clots in veins and arteries. Research has found that Coumadin may interact with certain foods, specifically those high in vitamin K, which may include limiting or avoiding certain vegetables and fruits.
Coumadin Interaction Information
Coumadin aids in stabilizing the international normalized ratio, or INR, and prothrombin time, or PT, lab values, which determine the time it takes for a clot to form. According to Drugs.com, Coumadin may interact with certain medications commonly prescribed for pain, fever and arthritis, such as acetaminophen, aspirin, ibuprofen and naproxen. Such medications may affect blood clotting and increase risk of stomach bleeding. Consumption of alcohol may increase side effects of Coumadin, while a high consumption of foods rich in vitamin K may decrease the effectiveness of Coumadin.
Vitamin K Information
The Institute of Medicine recommends that most individuals consume approximately 90 to 120 mcg of vitamin K daily. According to the Clinical Center at the National Institutes of Health, those individuals taking Coumadin should limit their vitamin K intake to those foods containing less than 60 percent of the daily value of vitamin K in order to keep INR and PT values within normal limits. Foods such as kale, spinach, turnip greens and collard greens contain more than or equal to twice the recommended daily value of vitamin K per 1/2 cup serving, and therefore should be limited to one serving per day in those taking Coumadin. Brussels sprouts, spinach, lettuce and broccoli also contain high amounts of vitamin K. In addition, foods such as liver and herbs such as tonka beans, sweet clover or sweet woodruff should be limited by those taking Coumadin.
Fruits to Avoid
According to Drugs.com, cranberries, cranberry juice, and cranberry herbal products should be avoided by those taking Coumadin. According to a 2010 study in the "British Journal of Pharmacology," consuming more than 16 oz. of cranberry juice daily should be avoided since such high dose effects need further research. A 2010 study in the "Journal of Young Pharmacists" found that lime fruit juice may reduce the anticoagulant effect of Coumadin and therefore should be avoided by those taking the medication. The U.S. Department of Agriculture identifies 1 cup of grapes as having about 23 mcg of vitamin K, 1 cup of raw blackberries or blueberries having 28 mcg of vitamin K, and one medium kiwi having about 31 mcg of vitamin K. Therefore, such fruits containing about 30 percent of vitamin K should not be eaten in excess, but may be eaten by those taking Coumadin without much concern.
Considerations
The Clinical Center at the National Institutes of Health recommends to those taking Coumadin to follow their prescription exactly, keep up on follow-up appointments to get INR and PT levels checked, and to contact health care professionals if there are any questions or concerns regarding their prescription or diet. It is important to keep vitamin K intake constant day to day while taking Coumadin and to avoid herbal products and dietary supplements that may affect vitamin K and Coumadin unless approved by a health care professional.
References
- Drugs.com: Coumadin Information
- Clinical Center: National Institutes of Health: Important Information to Know When You Are Taking Coumadin and Vitamin K
- Institute of Medicine: Dietary Reference Intakes: Vitamins
- "British Journal of Clinical Pharmacology"; Effect of High-Dose Cranberry Juice on the Pharmacodynamics of Warfarin in Patients; C.K. Mellen, et al.; July 2010
- U.S. Department of Agriculture: Vitamin K Content of Selected Foods per Common Measure
- "Journal of Young Pharmacists"; Evaluation of the Effect of Lime Fruit Juice on the Anticoagulant Effect of Warfarin; G. Adepoju, et al.; July 2010
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