Tuesday, April 30, 2013

Greens and Coumadin (aka. warfarin)

Photo credit:vegetable matter@blogspot.com

If I had a dollar for every time a patient told me (or I heard a doctor tell a patient) they "can't eat greens or salads because I take Coumadin," well, let's just say, I wouldn't have to keep this doctor thing up!  What's the matter with this?  Well, it's not true. [For those of you wondering what Coumadin (generic name, warfarin) is, a description follows.]
As a doctor who is focused on helping people eat better, you can imagine how crazy this drives me.  And, more importantly, how negative an impact this has on the health of millions of people.
Don't lose faith in your trusty medical providers if you've been told this along the way.  Avoiding greens used to be the standard teaching.  The thing about medical science is that it's constantly evolving and advancing.  As one of my professors said early on in medical school, "half of what I'm telling you will be proven wrong in the future - I just don't know which half."

What’s so special about greens?

Leafy greens are an important part of a healthy diet.  They're also an important part in cultural traditions throughout the world.  Greens add vitamin A, vitamin C, fiber, calcium, iron, potassium, B vitamins, other minerals, omega-3 fatty acids, many phytochemicals and phytonutrients  - and the cause of concern when it comes to Coumadin, but vitally important for health, vitamin K.  Vitamin K is necessary to keep bones strong, prevent heart disease and regulate bleeding and clotting.
Photo credit: www.wellbeingmag.com

Before I get carried away, I won’t assume everyone eats like a rabbit and knows what I mean when I say “greens.”  Greens are literally any green vegetable or herb. 

Some examples of greens

Examples of the hundreds (maybe thousands) out there are: kale, spinach, chard, watercress and other cress, lettuces, amaranth, celery, beet greens, turnip greens, collard greens, mustard greens, dandelion, cabbage, Brussels sprouts, broccoli, bok choy, rapini, endive, chicory, Jew’s mallow, Miner’s lettuce, cilantro, basil, parsley, sage, arugula, spring mix and other mixed baby greens, fiddlehead ferns, lovage, sorrel, sea kale, nori, chickweed, thyme, salsify, sea vegetables…I could go on and on!

Exposing the myth

Why did the "I can't eat greens" myth propagate so widely?  It's because greens DO interact with Coumadin.  I know this is confusing - stick with me.  
Coumadin is a blood thinner – called an "anti-coagulant" in medical terminology.  Millions of people take it to prevent blood clots that can cause death or serious injury due to stroke, blood clots in the lungs (called pulmonary emboli), leg pain and swelling, among other things.  People start taking it either temporarily, or permanently, depending on the reason it was started in the first place.  Some reasons people start taking Coumadin are that they have irregular heart rhythms, orthopedic surgeries (like hip replacement), artificial heart valves, previous blood clots in the legs or lungs, problems with the blood or diseases that cause increase risk of developing blood clots like lupus, factor V Leiden, polycythemia vera, just to name a few.  Cancers can also cause blood clots but are treated with a different type of anti-coagulant.

How vitamin K interacts with Coumadin

Vitamin K, in addition to the things mentioned above, is used to make components (called "clotting factors") in the blood that help the blood to clot. These clotting factors are made in the liver. When we eat foods or take daily vitamins with vitamin K in them, we don’t just use up the vitamin K and get rid of it.  Our bodies recycle vitamin K! Once vitamin K is used, it’s turned into an inactive (not useful) form of vitamin K. For the liver to use the vitamin K again, it needs to be converted back to an active (useful) form of vitamin K. Coumadin prevents the body from recycling inactive vitamin K to active vitamin K.  This basically makes most of the vitamin K in our bodies invisible or useless. 
The trick with Coumadin is to block just the right amount of vitamin K – not too little and not too much.  This makes the blood less likely than usual to clot, but not impossible.  We need some vitamin K active to make some clotting factors because if we weren’t able to clot our blood at all, we would bleed to death. It's a delicate balance.  People born with diseases of the blood that make clotting difficult, like hemophilia, live precariously with this problem.  If 100 people took Coumadin for 1 year, 7 would have major bleeding and 1 person would die from bleeding. It's very complicated to keep Coumadin at the right level because many things besides vitamin K affect it. Regulating the level often takes medical professionals who focus specifically on caring for patients taking this medicine at a Coumadin clinic.  Some doctors that have close relationships with their patients and see them frequently, adjust the dose themselves, but this is getting less common because of the amount of work involved.

Interactions with Coumadin

Greens are just one of the many, many things that interact with Coumadin – almost every medication both prescription and over the counter, alcohol, grapefruit juice, cranberries, multivitamins (especially vitamins A, C, E and K), some spices and seasonings (fenugreek, anise, garlic, ginger, horseradish, licorice, turmeric), many herbal and nutritional supplements, liver, natto (a Japanese food item), omega-3’s and green tea just to name a few. As you can imagine, completely avoiding everything that interacts is going to make life very tough to live!  Many of these things are difficult or impossible to give up.  

How to live your life healthfully AND keep a safe Coumadin level

For things that would have negative consequences for your health if given up - like greens, sources of omega-3 fatty acids, losing weight, antibiotics and other lifesaving treatments - don't give them up.  Not giving them up means that you need to work closely with your physician or Coumadin clinic to regulate your level. For things that are in your normal daily routine, work with your providers to stabilize your Coumadin level WHILE YOU CONTINUE TO use/eat them.  Then, BE AWARE WHEN CHANGES OCCUR to your routine and understand that some of those changes will require close medical follow up to make sure that your Coumadin level doesn't get too high or low.

Example 1, let's say you eat a green salad three nights per week and have collard greens with your Sunday meal.  That's a lot of vitamin K, right? (It is, trust me on this.) But remember, if this is your ROUTINE, let your doctors know and they can adjust your Coumadin accordingly and get it to a stable level.  Then, you only need to be concerned about greens (or any other thing that affects Coumadin levels) if you make a significant change.  
Example 2 - Let's say, it's a hot summer and you start eating large salads for one meal every day.  You've just doubled your intake of greens, and along with them doubled your intake of vitamin K.  You will likely need a higher dose of Coumadin than you did before you made this change.    
Example 3 - Your doctor gets the level adjusted and all is well until the fall. Suddenly, you crave the warm comfort of soups and stews while the crisp, coolness of salads seem less appealing.  You cut out salads completely, but keep collards with your Sunday meal.  Well, now you are getting only about one-seventh the amount of greens (and vitamin K) each week that you got in the summer.  You will definitely need a reduced Coumadin dose or risk life threatening bleeding.  
Example 4 - Similarly, it you got pneumonia and had to take antibiotics, you would need your Coumadin dose adjusted while on antibiotics.  
Example 5 - If you hurt your shoulder and needed to take tylenol, again, adjustment would be needed.
For most of you reading this who don't take Coumadin (and many who are), you're thinking, "this is too complicated!" Well, it's true.  Coumadin is one of the most complicated medications you can take.  No matter what your life choices, your Coumadin level will likely need regular adjusting.  Many, many people are stuck with this archaic medication regimen.  For some lucky patients who meet very specific criteria, there are some substitute drugs that are not nearly as difficult to regulate.  Unfortunately, they're expensive and they're not right for everyone.  

Big Picture

Photo credit: www.healthwisehome.com

Constant things don't usually require big dose adjustments, changes to your lifestyle, foods and medications/supplements often do. The key is to create routines and stick with them.  Notify your doctor or Coumadin clinic of any changes to that routine.  By doing this, you can maintain a normal, healthy lifestyle - including eating a healthy diet rich in green vegetables!


  1. I've been taking warfarin for 13 years and was constantly having to adjust the dosage. I started calculating my vitamin K intake daily 4 years ago and perhaps once a year it's changed by .5 µg. By setting a level of 700 µg daily I can have a decent serving of Swiss chard, kale, etc, or have a lower vitamin k food such as broccoli along with other greens, such as a salad. It takes some effort but much less than getting my blood checked every 4 or 5 days to adjust the warfarin level for what I had been eating (but not what I will be eating). I realize that my calculations are not scientifically accurate but over the course of a month the average out, particularly since I make a point of varying the types of greens I have. Because my inr is consistently in the desired range I only get my blood checked once a month,
    It's a great website; thank you for maintaining it. We need more doctors with your perceptiveness.

  2. I'm so glad you've found a way to eat greens and keep your INR in check and that this website has been helpful!

  3. Great article. In fact the best I have ever read. I had a Pulmonary Embolism which was misdiagnosed as "Pneumonia" by a doctor. I was on antibiotics for the 10 day series and became sicker and sicker. Rushed to the emergency room and not expected to survive, the alert pulmonary specialist told me that he thought I had an Embolism. I was told that my blood had the Lupus and the Factor 5 which meant I will be on Coumadin for the rest of my life. I eat a romaine salad every day. My numbers remain between the 2-3 safety zone. I learned to stick to the Romaine because mixed green salads raise my numbers. In the beginning it was terribly confusing to get the numbers right. In the beginning I had to have my blood tested daily for 2 weeks. Now 3 years later my numbers remain well within limits only if I continually have a romance salad.

    One question from your article is about Tylenol. I cannot take aspirin, I am told although a baby Aspirin I do take. But being in the 70's sometimes my bones ache according to the weather. I wish I could take Aleve which worked so well for me. But my doctor says ok and my nurse who monitors my blood levels says no. What do you think? Thanks for your wonderful article.


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