Most people who ask this question are taking warfarin (Coumadin).

Warfarin is used to treat people who need to have the body's blood clotting ability reduced. This includes people who have certain types of artificial heart valves, other heart problems, or who have had a blood clot in the leg or lungs.

Warfarin "thins" the blood by interfering with the production of vitamin K-dependent clotting factors. The right dose of warfarin varies from person to person and is sensitive to how much vitamin K the person takes in. An important way to keep blood clotting activity constant is to ingest the same amount of vitamin K daily.

Vitamin K comes from two sources -– from foods, especially vegetables, and from the normal bacteria that live in our intestines. Unless you take antibiotics that kill bacteria, the amount of vitamin K from bacteria remains quite constant. It is food sources that make a big difference.

Many different foods contain vitamin K. Green leafy vegetables have some of the highest amounts of vitamin K. The ones really high in vitamin K are:

• Kale
• Spinach
• Swiss chard
• Collard, turnip and mustard greens

Brussels sprouts and sprouts are good vitamin K sources, but the amount of vitamin K per ounce is not as high as the vegetables above.

Keep eating your vegetables. Just try to eat the same amount each day.