Does Peanut Butter Interact With Warfarin?

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Many foods interact with the anticoagulant warfarin, but peanut butter isn’t one of them. Foods with moderate or high vitamin K content can potentially decrease warfarin’s effectiveness. Certain vegetables, cooking oils, fruits and nuts are high in vitamin K and must be consumed with care, but peanuts and peanut butter contain little vitamin K and pose no such dangers. Work with your doctor to come up with a safe diet plan to complement warfarin therapy.

Vitamin K and Warfarin

Dietary vitamin K facilitates blood clotting and can make warfarin less effective. Consistency is key; the goal isn’t to avoid vitamin K-containing foods, but to consume the same amount of vitamin K regularly. To maintain a steady response to warfarin, avoid abruptly increasing or decreasing high-K foods in your diet. Your doctor can recommend a target range for vitamin K consumption.

Nuts and Vitamin K

The consensus among U.S. government sources is that peanut butter contains little or no vitamin K. Certain medical center patient guides may list peanut butter as a moderate source of vitamin K, but this is incorrect. Other nuts and nut butters, however, do provide appreciable amounts of vitamin K, especially pine nuts, cashews and hazelnuts. Almonds, Brazil nuts, macadamia nuts and walnuts contain little or no vitamin K.

High-K Foods

Foods with very high vitamin K content include kale, spinach, cooking greens, parsley and green onion. Pay attention to all vegetables, many of which contain moderate to high amounts of vitamin K. Margarine, olive oil and soybean oil are also rich in vitamin K. Among fruits, avocado, blackberries, blueberries, kiwifruit, prunes and figs have the most vitamin K. Multivitamins and nutritional supplement drinks may have added vitamin K -- check nutrition information labels before consuming them.

Other Interactions

Though not high in vitamin K, mango fruit, cranberry juice, pomegranate juice, soy milk and chewing tobacco may also interfere with warfarin therapy through mechanisms that are not fully understood. Check with your doctor before consuming these foods. Many common medications are dangerous to take with warfarin, including aspirin, ibuprofen, acetaminophen, other blood thinners, thyroid hormones, antibiotics and antifungals. Inform your prescribing physician about the medications, supplements and herbs that you take before starting warfarin therapy.