Which food should be avoided on warfarin therapy because it is high in vitamin K?

• A. Bananas
• B. Kale
• C. Oats
• D. Pasta

Answer: (B)

Warfarin works by blocking the recycling of vitamin K, which is needed to activate several clotting factors. Foods very high in vitamin K can counteract this effect, making the anticoagulation weaker and potentially destabilizing the INR. Kale is extremely rich in vitamin K, so it will significantly impact warfarin therapy if eaten in typical amounts, which is why it should be avoided or limited. The other options—bananas, oats, and pasta—contain relatively low amounts of vitamin K and do not markedly affect warfarin’s action when consumed consistently. The key idea is to maintain a steady vitamin K intake and adjust warfarin dose under medical guidance if your diet changes.