Coumadin is the trade name of the blood-thinning drug warfarin. Taking this medication reduces the coagulability of your blood, meaning the drug interferes with clot formation. Your diet may influence the effectiveness of Coumadin or its elimination from your body. Therefore, you need to monitor your intake of certain foods and avoid others if you take Coumadin.
The Vitamin K-Coagulation Connection
Vitamin K is a fat-soluble micronutrient that you obtain almost exclusively from your diet. Unlike other vitamins that have many metabolic roles, the primary function of vitamin K is working as a required cofactor in the production of your coagulation factors. These proteins join together to form the gel-like material that is the main component of blood clots. By blocking the action of vitamin K, Coumadin interferes with production of the coagulation factors, making your blood less likely to clot.
Influence of Dietary Vitamin K on Coumadin Dose
Your dosage of Coumadin has to be carefully adjusted to get the desired effect. You need enough medication to prevent the formation of clots in your blood vessels, which can damage your tissues by obstructing blood flow. The dose cannot be too high, however, or you may bleed excessively if you sustain an injury. Your dietary intake of vitamin K is an important factor that influences how much Coumadin you need to get the appropriate level of anticoagulation. The right dose of Coumadin for you is the one that produces the desired degree blood thinning, given your dietary intake of vitamin K.
Maintaining a Stable Vitamin K Level
To maintain a stable vitamin K level that "matches" your Coumadin dose, you must consume roughly the same amount of vitamin K each week. The main concern is vitamin K-rich foods, including green leafy vegetables and cruciferous vegetables, such as cauliflower, Brussels sprouts, cabbage and broccoli. You can eat these nutritious foods while taking Coumadin, as long as you eat approximately the same amount each week. Your doctor will advise you about what foods to monitor and may recommend that you limit your intake of certain foods that contain exceptionally high concentrations of vitamin K, such as spinach, kale and collards. If you have questions about your diet while on Coumadin, talk with your doctor.
Coumadin and Cranberries
Chemicals found in cranberries may interfere with the normal breakdown of Coumadin, potentially causing a buildup of the drug in your system. High levels of Coumadin may thin your blood too much, putting you at risk for excessive bleeding. To avoid this potential complication of Coumadin therapy, your doctor may advise you avoid cranberries and cranberry juice while taking this medication.
References
- "Chest"; Oral Anticoagulants: Mechanism of Action, Clinical Effectiveness, and Optimal Therapeutic Range; Jack Hirsh, M.D., et al.; January 2001
- Oregon State University Linus Pauling Institute; Vitamin K; Jane Higdon, Ph.D.; May 2004
- Drugs.com: Warfarin Prescribing Information
- "American Journal of Health-System Pharmacy"; Interaction Potential Between Cranberry Juice and Warfarin; David Q. Pham, Pharm.D., Antony Q. Pham, B.S., B.A.; March 2007
- National Institutes of Health; Important Information to Know When You are Taking Coumadin and Vitamin K; December 2003
- University of Michigan Health System; Warfarin (Coumadin™), Patient Education Handout Associated with UMHS Clinical Care Guideline; UMHS Clinical Care Guidelines Committee; January 2009
