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Warfarin and Green Leafy Vegetables Can Be OK

Warfarin was the first prescribed anticoagulant. Now we have Eliquis and Xarelto. They're pricey! Is it safe to combine warfarin and green leafy vegetables?

For decades, patients taking the anticoagulant warfarin, known by the brand name Coumadin, have been admonished to be very careful about consuming foods rich in vitamin K. That’s because too much vitamin K could theoretically counteract the blood thinning properties of warfarin. In practice, this meant that many patients were told that warfarin and green leafy vegetables could be dangerous and lead to blood clots. Many people avoided green leafy vegetables like kale, collards, spinach or broccoli, even though they are heart healthy.

A Change of Heart?

Now a new study from Montreal suggests warfarin and green leafy vegetables should not be considered deadly (Nutrition 2019, The Annual Meeting of the American Society for Nutrition, June 8-11, 2019). The experts who conducted this research suggest that people would do better to eat more green leafy vegetables if they keep their vitamin K intake consistent.

What They Did:

The trial involved 46 patients taking warfarin. They all had a history of difficulty maintaining consistent anticoagulant activity. For six months half of the patients were given nutrition and cooking classes with a general focus on improving nutrition. They were the controls.

The other half received nutrition and cooking classes focused on increasing the amounts of green vegetables and other vitamin-K rich foods in the diet. After six months, half of those who had increased their vitamin K intake had stable anticoagulant levels.

In contrast, only one-fifth of the control group were able to achieve stability. The conclusion:

“Increasing VK [vitamin K] intake ≥150 µd/day through diet strategies improves anticoagulation stability of W [warfarin]-treated patients with a history of anticoagulation instability.”

Making Sense Warfarin and Green Leafy Vegetables:

We’ll bet you have no idea how much vitamin K you consume daily. Your package of broccoli or kale does not list how much vitamin K is in a serving. We’ve got you covered. Our FREE Guide to Coumadin Interactions lists the vitamin K content of dozens of familiar foods.

For example:

  • 3.5 ounces of raw kale has 817 mcg of vitamin K
  • 0.5 cup of cooked spinach has up to 360 mcg of vitamin K
  • 0.5 cup of cooked collards has 440 mcg of vitamin K

You can find out about more about vitamin K and green leafy vegetables in our free Guide to Coumadin Interactions at this link.

You will also learn about medications that can interact with warfarin.

Perhaps it is time for health professionals to counsel their patients taking warfarin to eat more green leafy vegetables rather than fewer and maintain a consistent intake of vitamin K daily. It is also important to have periodic blood tests to make sure your anticoagulation activity is in the sweet spot!

Nutrition 2019, The Annual Meeting of the American Society for Nutrition, June 8-11, 2019.

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About the Author
Joe Graedon is a pharmacologist who has dedicated his career to making drug information understandable to consumers. His best-selling book, The People’s Pharmacy, was published in 1976 and led to a syndicated newspaper column, syndicated public radio show and web site. In 2006, Long Island University awarded him an honorary doctorate as “one of the country's leading drug experts for the consumer.” .
Coumadin Interactions

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Coumadin Interactions
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My husband, who has been on Coumadin since 2008, has eaten raw spinach and leafy greens every day with no problem. He does, of course, have regular bloodwork done.

Did the people who increased their intake of vitamin K foods at a consistent level also have to take higher doses of coumadin? I don’t like that possibility.

My husband and I both take warfarin, have since about 1997. Our cardiologists have all told us that we can eat green vegetables, but try to keep it to 3 servings a week. Over the years we learned that blueberries and asparagus and some other foods we did not realize, also contain Vit. K. More recently, I learned that taking a small serving of a vitamin mineral powder containing Vit. K daily, helps keep the INR readings consistent. We cannot use the newer drugs, but even if we could, I would prefer the warfarin. It is cheaper, and it has a readily-available antidote: in an emergency, I can use a quick serving of Vit K to counteract bleeding caused by an accident of some kind.

Warfarin works fine for me. I just have to work with primary care office to get INR checked once a month. I have my Warfarin dose adjusted so I can eat plenty of Vitamin K veggies and cashew nuts, which are rich in vitamin K. Eliquis would eliminate the need for INR checks but have to watch for drug interaction. Not sure of this but took Eliquis, and it elevated my Dilantin levels which I take for seizures.

I graduated from nursing school in 1994. At that time, we were being taught to instruct our coumadin clients to be consistent in their vitamin K-rich food intake. It wasn’t till a couple of years later that I found clients who were being told “no vitamin K-rich food”. Maybe doctors thought people were too stupid to be consistent.

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