If you are at risk of developing blood clots, your doctor may prescribe the drug warfarin, sold under the brand name Coumadin. The blood thinner may decrease your chances of stroke or heart attack. A wide range of prescription drugs, over-the-counter pain medicines and herbal supplements have been cited as either counteracting or dangerously accelerating warfarin’s effects. Some vitamin supplements and foods can also cause warfarin resistance. Always talk to your doctor to determine which drugs, dietary supplements or foods you need to avoid or decrease while on prescription medication.
Vitamin K
Vitamin K was named for “koagulation,” the German word for coagulation. Given its fame in helping blood to clot, it’s not surprising that vitamin K is the nutrient most often noted as a possible antagonist for the blood thinner warfarin. For the general population or for people experiencing heavy blood loss after surgery or during menstruation, vitamin K can be a useful nutrient. But for people who need to thin their blood, rather than to encourage a coagulant effect, extra vitamin K can be counteractive to warfarin’s effectiveness.
Foods to Limit
Some cooking greens offer several day’s worth of the vitamin K recommended for the general population, notes the Office of Dietary Supplements. A 1/2 cup serving of cooked kale, for example, provides 660 percent of the daily value for vitamin K. Other cooked greens containing at least twice the daily value for vitamin K include Swiss chard, collard greens, spinach, turnip greens and mustard greens. Using about 1/4 cup of the fresh herb parsley will deliver about 300 percent of the daily value of vitamin K. Vegetables with at least 100 percent of the nutrient in an average serving include brussels sprouts and uncooked vegetables, such as spinach, broccoli and dark green lettuce varieties. Consider using cooking oils other than olive, soybean or canola, which are high in vitamin K.
Considerations
If greens are a significant part of your diet, or you were taking vitamin K supplements, talk to your doctor about stepping down from the nutrient. A significant or sudden decrease in vitamin K from your system might amplify warfarin’s effects to a dangerous extent, notes the Office of Dietary Supplements. The Office of Dietary Supplements recommends keeping your intake of the vitamin consistent, and limiting foods high in vitamin K to one serving a day. Eat foods with moderately high vitamin K no more than two or three times a day.
Vitamin C Caution
Interactions between warfarin and vitamin C are not as well documented as those between warfarin and vitamin K. Some researchers believe warfarin resistance in some patients may be due to overusing vitamin C supplements. Because concern centers on high doses of vitamin supplements, rather than on foods rich in vitamin C, limiting foods like orange juice, citrus fruits or tomatoes is not considered necessary for warfarin patients. Tell your physician if you consistently or occasionally take vitamin C tablets.
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