Nutrition Information Regarding Coumadin®
(Warfarin) Therapy

A number of dietary–related factors can affect your medication. It is important that you are aware of these in order to keep the effect of Coumadin® consistent.

The production of some clotting factors is dependent upon the availability of vitamin K. Without vitamin K, some of these clotting factors may be produced but are not active in clotting. Therefore, people who are vitamin–K deficient will have a bleeding tendency. Coumadin works to increase the time it takes for blood to clot (thinning the blood) by interfering with the action of vitamin K. So, while on Coumadin, the amount of vitamin K in your diet is important, as increasing amounts of vitamin K will work against the action of Coumadin. As you can see, the amount of vitamin K in the diet can impact the effects of Coumadin.

The most important point to remember is to keep the amount of vitamin K you consume in your diet fairly consistent. Swings in intake of vitamin K may cause the PT/INR (the laboratory test that measures the effect of Coumadin) to change. You do not need to eliminate foods containing vitamin K from your diet, however, be aware of foods that are particularly high in vitamin K, and try to keep the amounts fairly consistent on a daily basis.

Note: The average person in the U.S. consumes about 60-80 micrograms (mcg) of vitamin K per day. One microgram is one–millionth of a gram. Thirty grams equal one ounce. Variations in small amounts of vitamin K can have a significant effect on PT/INR time in some patients. It is not necessary for most people to count vitamin K micrograms. However, if you are someone who is having difficulty stabilizing your PT/INR times, you may benefit by recording your daily intake of vitamin K to ensure that your daily intake is consistent.

Vitamin K–Rich Foods

As a Coumadin patient, suddenly increasing or decreasing the vitamin K content in your diet can change the effectiveness of your medication. Aim for consistency! Eat a balanced diet, with a variety of foods. If your normal pattern is, for example, to have two servings per day of food high in vitamin K, then make sure that you continue with this pattern every day. If you do not normally eat these foods, do not suddenly eat a large amount of them.

The following foods are very high in vitamin K and should be avoided (if you eat them one day and not the next, your medication may be affected):

Kale, parsley (except as a garnish – a sprig or a tablespoon chopped), Swiss chard, seaweeds, mint leaves, natto (a Japanese fermented soybean product).

The following foods are high in vitamin K – they contain 60–400 + mcg. of vitamin K per serving (for vegetables, this would be 1/2 cup cooked, or 1 cup raw):

Avocado (1/8th of an avocado), broccoli, brussel sprouts, cabbage (fresh or boiled), collards, endive, lentils (1/2 cup), lettuce (head, bib, leaf), liver (3.5 oz.), garbanzo beans (3/4 cup), green onion, green pepper, soybeans (3/4 cup) – but not tofu, spinach, turnip greens (and other greens), watercress.

The following foods have a moderate amount of vitamin K – they contain 3-59 mcg. of vitamin K per serving (for vegetables, this would be 1/2 cup cooked, or 1 cup raw):

Canola and soybean oil (2 tbsp.), margarine (2 tbsp.), mayonnaise (2 tbsp.), green apple, asparagus, celery, iceberg lettuce, okra, peanut butter (2 tbsp.), summer squash.

Dietary Changes

When you start taking Coumadin, eat your usual amount of vitamin K–containing foods while your doctor finds the right dose for you.

Any time your diet changes significantly, your vitamin K intake is likely to be affected. Tell your doctor if you change your vitamin K food pattern, so your INR can be monitored more closely.

Examples of changes that would affect the vitamin K content of your diet are when you…

• Go on a weight reduction diet and your intake of vegetables increases.
• Eat more fresh vegetables in the spring and summer because of the larger selection.
• Are sick and unable to eat solid foods for a few days.
• Have been in the hospital and on a limited diet due to surgery or illness, and return home to your normal diet.
• Travel to a place where the foods are unfamiliar, and your diet changes as a result.
• Decide to make a change in your diet that results in an increase of your intake of lentils, beans, dried peas, and vegetables.

Important Dietary Tips

• Please take into account that some multiple vitamins contain vitamin K. Check all vitamins carefully, and inform your physician if your vitamin contains vitamin K, and the amount that it contains.
• Dried basil, thyme and oregano contain high levels of vitamin K. However, a teaspoon of these herbs in their fresh form contains only a small amount.
• Store–bought margarine and mayonnaise contain unknown quantities of various vegetable oils; as a result, the amount of vitamin K in these foods is unpredictable. So use small amounts of butter instead of margarine. Mayonnaise should be homemade with oils that are lower in vitamin K. If prepared products are used, they should be the “light” variety and used in very small portions (no more than several teaspoons).
• For the same reason, be cautious of store–bought salad dressings. Homemade dressings are preferred.
• Watch out for foods normally low in vitamin K but packed in oil (such as tuna fish), especially when the type of oil is unknown. It is best to use canned items packed in water.
• The vitamin K content of food is not altered by cooking or gamma irradiation.
• Exposure of oils to sunlight or fluorescent light destroys approximately 85% of the vitamin K. You can expose high vitamin K oils to light for at least 48 hours by placing them in a transparent container in the sunlight. The oil does not need to be open to the air, as oxygen will cause it to oxidize.
• DO NOT EAT GRAPEFRUIT OR DRINK GRAPEFRUIT JUICE. Grapefruit and grapefruit juice decrease the body’s ability to metabolize Coumadin.
• Avocados can unpredictably alter the PT/INR. Avocados are high in vitamin K. The amount of vitamin K varies from avocado to avocado. The vitamin K content in products such as guacamole can vary by as much as 40 times.
• Alcohol can alter your response to Coumadin. Discuss alcohol use with your physician.
• Vitamins A, E and possibly C may affect how your Coumadin works. The amounts in a multiple vitamin are not a problem, however. Discuss taking vitamin supplements beyond a multiple vitamin with your doctor.

Herbal Products

Use caution with herbal supplements, as they may interfere with Coumadin. The following herbs have either been reported to affect Coumadin activity or to affect blood clotting on their own:

Chamomile, echinacea, Saint John’s wort, garlic, feverfew, ginkgo biloba, ginseng, ginger, saw palmetto, alfalfa, angelica, aniseed, arnica, asafoetida, fenugreek, horse chestnut, melilot, prickly ash, quassia, red clover, sweet woodruff, tonka beans.

Resources

The following web site is sponsored by DuPont Pharmaceuticals, the maker of Coumadin, and is an excellent resource for information relating to Coumadin: www.coumadin.com.

The Coumadin Cookbook gives the vitamin K content of hundreds of recipes and foods. The goal of this book is to teach the person on Coumadin to easily consume the same amount of vitamin K each day in a heart–healthy way. A link detailing more about this useful resource for patients on Coumadin, including ordering information, can be found at: www.coumadincookbook.com.