Heart Health

Updated 27 September 2016

Warfarin and your diet

Be warned: what you eat can have an effect on Warfarin - a powerful and very popular anticoagulant drug.

Warfarin is an anticoagulant often prescribed to prevent the formation of blood clots in the vessels, and their movement to other parts of the body.

While the foods you eat can have an effect on how well warfarin works for you, there are also drug-drug interactions that can have an effect. If you’re on warfarin, you shouldn’t take aspirin or ibuprofen as these medications could increase the risk of bleeding. You can take paracetamol, but you need to stick to the recommended dosages very carefully.

You should have regular blood tests when taking warfarin in order to test your International Normalised Ratio (INR). If your INR is high, you have an increased risk of bleeding. If it’s too low, you have an increased risk of blood clotting.

There are several foodstuffs that can interfere with the working of warfarin in your body.

Doctors recommend that you don’t make any major changes to your diet when starting to take warfarin. However, there are certain foods to avoid or limit.

Any foods that contain large amounts of vitamin K can lessen warfarin’s effectiveness, especially if not eaten in consistent weekly amounts. You don’t have to avoid these foods, but do take care not to have a large amount of it in one week, and nothing the following week. These foods include green, leafy vegetables, such as Brussels sprouts, spinach, broccoli and parsley. Green tea has the same effect, and so do cauliflower, cooked chickpeas, cooked lentils, beef liver and cooked soybeans.

The following foodstuffs don’t have such a serious effect, but shouldn’t be eaten in great quantities, or irregularly:

• Cooked asparagus
• Cooked green beans
• Raw green onions
• Lettuce
• Cooked cabbage
• Raw celery
• Green apples
• Pistachio nuts
• Soybean oil
• Rolled oats
• Wheat bran
• Wheat flour
• Wheat germ
• Chicken liver
• Pork liver
• Coffee

The following foods are low in vitamin K. One cup of the foods of your choice can be eaten per day without having an effect on the effectiveness of the warfarin you may be taking:

• Sweet corn (raw or cooked)
• Onions (raw or cooked)
• Pumpkin (cooked)
• Squash and butternut (cooked)
• Potatoes (cooked)
• Sweet potatoes (cooked)
• Aubergine (cooked)
• White mushrooms (raw or cooked)
• Tomatoes (raw or cooked)
• Cucumbers (raw)
• Iceberg lettuce

Drinks that can increase the effect of warfarin include cranberry juice and alcohol. It’s especially dangerous to binge drink while you’re taking warfarin, as alcohol increases the effect of the warfarin, which means it could increase the risk of bleeding.

When you’re taking warfarin, it’s essential to go for regular blood tests, to avoid foods that may be harmful, and to speak to your doctor or pharmacist before taking any over-the-counter medications.

- (Susan Erasmus, Health24)

References: mayoclinic.org: nhs.uk; webmd.com


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