Doctors prescribe warfarin to help thin the blood of people at risk for blood clots that could cause strokes or heart attacks. Warfarin helps keep your blood from clotting, but getting the proper dose is important to limit the risk of excessive bleeding. Some foods, including green leafy vegetables, can interfere with warfarin if you consume too much of them.
Leafy Green Vegetables
Leafy green vegetables, including spinach, kale, collard greens, mustard greens, Swiss chard, Brussels sprouts, parsley, lettuce, broccoli and endive, are very healthy, providing you with fiber and lots of vitamins and minerals, including large amounts of vitamin K. However, if you take warfarin you need to watch your intake of these vegetables, as they can interfere with warfarin and make it less effective.
Vitamin K and Warfarin
Warfarin works by interfering with the blood clotting function of vitamin K, according to the National Institutes of Health, so if you consume too much vitamin K or too little vitamin K your blood may clot too quickly or too slowly. Vitamin K intake while on warfarin should remain consistent.
Amounts to Consume
To keep your vitamin K intake consistent, women should consume approximately 90 mcg per day and men 120 mcg per day, the Mayo Clinic recommends. Limit foods containing 200 percent or more of the daily value for vitamin K to one serving or less per day and foods containing between 60 percent and 199 percent of the daily value to three servings or less per day. Most green leafy vegetables fall into one of these two categories, with 1/2 cup of cooked greens falling in the first category and 1 cup of raw greens falling into the second category.
Considerations
If you have difficulty maintaining a consistent intake of vitamin K, you may want to ask your doctor to switch you to a different blood thinner, as some types of blood thinners are not affected by vitamin K intake. Consuming cranberry juice, alcoholic beverages, vitamin E supplements, antibiotics and certain herbal medicines can also affect warfarin function.
