Prescription drugs often interact with each other and with the foods you eat. It is the patient's responsibility to understand which foods should be consumed or avoided while taking a prescription drug. This is especially true for patients undergoing Coumadin therapy, as drug-food interactions can potentially lead to a heart attack, stroke or other life-threatening complication.
Significance
Coumadin is a brand name prescription drug containing warfarin sodium. It is generally taken once a day, and patients have frequent laboratory tests to ensure their warfarin levels are therapeutic without being too high or too low. Doctors prescribe Coumadin to prevent blood clots in patients with an increased risk of dangerous clotting. It works by lowering the activity of a clotting agent, vitamin K. Maintenance of a stable level of vitamin K is important for warfarin users.
NIH Guidelines on Leafy Greens
Most, if not all, leafy green vegetables contain some amount of vitamin K. According to the National Institutes of Health, those with high levels include mustard greens, turnip greens, kale, collard greens, Swiss chard and spinach. Consumption of boiled quantities of these foods should generally not surpass 1/2 cup each day. The NIH also advises not eating more than 1/4 cup of raw parsley, also considered a high-level vitamin K food, each day while taking Coumadin.
Some leafy greens fall into the category of moderate level vitamin K foods. These include a cup of raw green leaf lettuce, raw Romaine lettuce or raw endive lettuce. One cup of chopped raw spinach or raw chopped turnip greens also fall into this category. Three servings of these moderate level vitamin K leafy greens per day is acceptable, according to the NIH.
NIH Guidelines on Other Vegetables
The NIH advises that a 1 cup serving of raw broccoli contains a moderate amount of vitamin K. A 1/2 cup serving of Brussels sprouts is also considered a moderate vitamin K food. These foods, along with the moderate level vitamin K leafy greens, should be limited to a total of three servings a day. For example, one serving of Brussels sprouts, one serving of raw broccoli and one serving of raw spinach in a day is the maximum acceptable limit under NIH guidelines.
Green Tea
The Mayo Clinic advises individuals taking warfarin not to consume a large amount of green tea, which contains vitamin K. The amount of the vitamin may vary according to the way the tea is prepared. It is important to read the ingredient label on any tea consumed, as some teas that appear dark actually contain a percentage of green tea.
Other Dietary Limitations
Some foods are limited for individuals taking warfarin for reasons other than vitamin K. Cranberry juice might be off limits, and alcohol may be prohibited, limited to one drink per day or limited to three drinks per day, depending on the patient's condition. Some clinicians recommend restricting caffeine products, including coffee, tea, caffeinated soda and foods and beverages containing chocolate. Vitamin supplements, dietary supplements, over-the-counter medications and herbs should only be taken with the consent of the physician who manages the warfarin therapy.
Warning
Despite the guidelines from the NIH, a patient taking Coumadin should seek the advice of his physician regarding his particular needs. Because foods rich in vitamin K contain a variety of important nutrients, patients are often encouraged to eat them as described, rather than abstain. It is also important that someone who has been consuming these foods regularly not stop eating them suddenly without advising his physician.
