Coumadin, which is the brand name of the prescription anticoagulant medication warfarin, is subject to interactions with several types of food and health supplements. Finding the right dose of Coumadin can be tricky, because the dose must be large enough to reduce the risk of blood clots, but not so large that the risk of excess bleeding is increased. Several foods, including certain types of meat, can alter the activity of Coumadin, requiring alterations in dose to maintain the delicate balance of effectiveness. If you are taking Coumadin, be sure to ask your doctor before radically changing your diet.
Coumadin and Vitamin K
Coumadin slows blood clotting by inhibiting the activity of vitamin K, a critical factor in the formation of blood clots. Eating foods that contain large amounts of vitamin K can counteract the effect of Coumadin, rendering it less effective and increasing the risk of blood clots. While you do not have to avoid foods containing vitamin K altogether, you do need to avoid eating massive amounts of vitamin K-rich foods in a single sitting.
Vitamin K Levels in Meat
Most cuts of meat, including beef, ham, chicken, pork and turkey, contain relatively low levels of vitamin K and do not pose a large risk of interacting with Coumadin. However, organ meats, including beef and chicken liver, contains very high levels of vitamin K. Use caution eating these meats while taking Coumadin, and take care not to combine them with other foods high in vitamin K such as green vegetables like broccoli and Brussels sprouts.
High-Protein Diet
Reports are emerging that following a low-carbohydrate, high-protein diet can interfere with the activity of Coumadin, explains an article published in the April 2008 issue of the medical journal "Pharmacotherapy." In at least three cases, patients who were taking Coumadin and started a high-protein diet experienced a drop in the effectiveness of the medication and had to increase their doses by 16 to 30 percent. Although these results are preliminary and need confirmation by clinical trials, you may want to monitor the levels of meat and other high-protein foods in your diet while taking Coumadin.
Mechanism
Doctors are not sure exactly why a high-protein diet may reduce the effectiveness of Coumadin. One possible reason is that high-protein diets raise levels of a protein called cytochrome P450. In your liver, cytochrome P450 breaks down drugs like Coumadin and removes them from the bloodstream. By increasing levels of P450, a diet consisting of large amounts of meat and other high-protein foods may increase the breakdown of Coumadin and decrease its effectiveness, explains the article published in "Pharmacotherapy."
References
- "Pharmacotherapy"; Potential Interaction Between Warfarin and High Dietary Protein Intake; L.B. Hornsby et al.; April 2008.
- "Annals of Pharmacotherapy"; Decreased Warfarin Effect After Initiation of High-Protein, Low-Carbohydrate Diets; S.J. Beatty et al.; April 2005
- Agency for Healthcare Research and Quality: Blood Thinner Pills; August 2010
- University of Michigan Health System: Warfarin (Coumadin®) and Your Diet; 2010
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