The prescription drug warfarin or coumadin prevents clot formation in patients with atrial fibrillation, mechanical heart valves and peripheral vascular disease. Warfarin works by blocking certain chemical reactions in the clotting pathway of the body. Patients on warfarin will have regular blood tests to check their PT/INR values. These values indicate how warfarin is working in the body. When taking warfarin the PT/INR will be elevated. Warfarin is an effective anticoagulant but certain foods and vitamins negatively interact with warfarin and should be avoided.
Green Leafy Vegetables
Green leafy vegetables contain vitamin K. The average daily adult intake of vitamin K in the United States is about 70 to 80 micrograms per day. The daily recommended value is 80 micrograms per day. The National Institutes of Health.gov advise patients taking warfarin to keep daily intake of vitamin K to 60 percent or less of the daily value to prevent a decrease in the PT/INR. Foods such as kale, collard greens, spinach and parsley contain more than 200 percent of the daily value of vitamin K and should be limited to one serving per day. Brussels sprouts, iceburg lettuce and broccoli contain 60 to 199 percent of the daily recommended value.
Vitamin E
According to the National Institutes of Health website, evidence suggests that vitamin E has blood thinning effects. Taking more than 1000 international units, IU, increases the risk of bleeding. The institute notes that it may be safe to ingest up to 800 IUs per day, but warns patients taking warfarin should discuss the use of vitamin E supplementation with their health care provider.
Cranberries
Drugs.com also notes that patients on warfarin should avoid eating cranberries, drinking cranberry juice or taking cranberry herbal products. Cranberries can intensify the effect of warfarin and make the blood very thin. The risk of gastrointestinal bleeding increases when the PT/INR becomes excessive.
Alcohol
Patients taking warfarin should avoid alcohol. According to Drugs.com alcohol increases the effect of warfarin. Consuming alcohol also increases the risk of falling which can lead to a head injury. Fatal subdural hematomas or bleeding on the brain have occurred because of alcohol intoxication and the exacerbated anticoagulant effect of warfarin.
