The human body produces some of its own vitamin K, but most comes from food. People taking anticoagulant medications such as warfarin, brand name Coumadin, need to follow a vitamin K regulated diet. This does not mean eliminating vitamin K from the diet, but keeping intake consistent from day to day.
Function
Vitamin K is important for bone structure and strength, as well as for nervous system function and general cell health, according to the Linus Pauling Institute, or LPI, at Oregon State University. It is also essential for proper blood clotting, as the liver uses vitamin K to make prothrombin, a protein involved in the clotting process.
Warfarin
People with certain medical conditions, such as some types of arrhythmia, are at increased risk of developing blood clots, which can lead to heart attack and stroke. Some oral anticoagulants, the most common being warfarin, inhibit blood clotting by interfering with the action of vitamin K in the production of prothrombin. People who take warfarin must have regular blood tests to check a measurement called prothrombin time, or pro time, to ensure a correct warfarin dosage, explains Jackson/Siegelbaum Gastroenterology. Too high a dose can cause excessive bleeding and too low a dose makes the drug ineffective.
Effects
If you take warfarin and eat more vitamin K than usual, this decreases the effectiveness of warfarin. In contrast, if you eat less vitamin K than usual, it can lead to unwanted bleeding. Because vitamin K is essential for health, you cannot eliminate it from your diet. The Food and Nutrition Board of the Institute of Medicine has established the adequate intake level for vitamin K at 90mg per day for a woman 19 years of age and older, and 120mg per day for men 19 years of age and older. Pregnant and breastfeeding women need more. A vitamin K diet involves not making large changes in the amount of this vitamin you consume from day to day. This keeps blood clotting function consistent with the same medicine dosage each day.
Vitamin K Foods
Leafy green vegetables contain the largest amounts of vitamin K, according to Jackson/Siegelbaum Gastroenterology. Many vegetables provide the same amount or more of the daily adequate intake amount for vitamin K in just one serving. People shouldn't eat a large amount of these foods on one day if they don't do so every day. These foods include asparagus, broccoli, Brussels sprouts, green cabbage, collard greens, endive, scallions, spinach, Swiss chard and watercress.
Tips
Rather than eating a large salad of green vegetables once in awhile, which can disrupt the action of warfarin, other options are available, notes licensed dietitian Joanne Larsen at Ask the Dietitian. She suggests including low-to-moderate sources of vitamin K such as avocado, beets, carrots, peeled cucumbers, mung bean sprouts, peas, radishes, red cabbage, red and orange peppers, tomatoes, white mushrooms, and cooked dried beans such as garbanzo or red kidney beans.
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