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Vitamin K

Taking Warfarin? The Myth about Foods with Vitamin K

Are you taking the blood thinner warfarin to manage your risk of clots and A-Fib stroke? Have you been told to avoid foods with vitamin K to prevent excess clotting? Want to know the facts about warfarin and vitamin K? Take our 5 question quiz to separate the facts from the myths.

A 5 Question Quiz about Warfarin and Vitamin K

1. True or False: Warfarin and vitamin K actually work against each other in your body.
True. Vitamin K helps your blood clot. Warfarin makes your blood clot more slowly. Your INR level is monitored to keep them in balance.

2. True or False: When taking warfarin, you should limit foods with high levels of vitamin K like dark, leafy greens.
False. You don’t need to avoid foods with vitamin K. The key is to consistently maintain your daily level of vitamin K.

Don’t confuse vitamin K with the K on the periodic table for potassium. One’s a vitamin, the other is a mineral.

3. True or False: Vitamin K information is not included on most packaged food nutritional labels.
True. So it’s often hard to determine the amount of vitamin K in your food.

… Continue with the quiz…->

Arterial Calcification From Warfarin: Vitamin K May Reverse it

The blood thinner, warfarin (Coumadin) is a “vitamin K-antagonist” which works by blocking vitamin K thereby affecting several steps in the anticoagulation pathway and decreasing clotting proteins in the blood.

Graphic: Warfarin and vitamin KBut vitamin K is essential for heart and bone health. Without enough K-2, osteocalcin, a protein that binds calcium to bone, doesn’t function. “When calcium doesn’t stay in bones, it can end up clogging your arteries, causing a heart attack or stroke.” Vitamin K functions to keep calcium out of soft tissues.

In one study, people with the lowest blood levels of vitamin K-2 had a 57% greater risk of dying from heart disease than those with the highest levels. They were also at increased risk for osteoporosis and bone fractures.

Why I Warn Against Taking Warfarin

In a study of 451 women using mammograms to measure arterial calcification, after just one month of warfarin use, arterial calcification increased by 50% compared to untreated women. After five years, arterial calcification increased almost 3-fold.

To avoid arterial calcification, if you are on warfarin (Coumadin), talk to your doctor about switching to Eliquis (apixaban) which tested the best of the NOACs and has the best safety test results. (See my article, Warfarin and the New Anticoagulants.)

Research: Vitamin K Reverses Arterial Calcification from Warfarin

If you have been on warfarin for a while, you will be interested in the evidence that high doses of vitamin K may reverse arterial calcification.

An analysis of kidney failure patients on dialysis found over 50% had vascular calcification (one devastating side effect). A clinical study tested supplementation with vitamin K2 (MK-7) over a six-week period. In the group given 360 mcg of MK-7, the favorable response rate was a remarkable 93%. (When supplementation ceased, these high-risk patients were once again vulnerable to vascular calcification.)

There are three forms of vitamin K: vitamin K1, vitamin K2(MK-4) and vitamin K2(MK-7).

An animal study involved groups of rats who were all initially fed a six-week diet of warfarin to induce calcium buildup in the blood vessels. This was followed by some groups receiving high-dose vitamin K1 or K2 (MK-4).

In six weeks, not only was there no further arterial calcium accumulation, there was a 37% reduction of previously accumulated arterial calcification. After 12 weeks, there was a 53% reduction. The high-dose vitamin K1 and K2 groups also showed a reversal in carotid artery stiffness.

Warfarin - Coumadin tablets various dosages

Warfarin (brand name Coumadin) various dosages

If on Warfarin, You’re Deficient in Vitamin K

According to the U.S. Department of Agriculture (USDA), the recommended range of normal vitamin K intake ranges between 60-80 micrograms for women and 80-120 micrograms for men. (The typical recommended supplement dosage is 90 mcg females, 120 mcg males.)

Nearly everyone is deficient in vitamin K. While most of us may get just enough vitamin K from our diet to maintain adequate blood clotting, most of us should increase our intake of vitamin K through foods like leafy greens, or take vitamin K supplements.

You must always take your vitamin K supplement with fat since vitamin K is fat-soluble and won’t be absorbed without it. Dr. J. Mercola

But if you’re on warfarin, you are NOT getting enough vitamin K to protect you from arterial calcification and a variety of other heart health problems. And certainly not enough to reverse the effects of warfarin on soft tissue calcification.

Counteract Arterial Calcification: What Dosage of Vitamin K?

So the question arises, is there anything we can do to reverse arterial calcification? What amount of vitamin K should you be getting? Sadly, we don’t have enough human research as to the correct dosage, but we do have some indications.

Referring back to the study above with rats, the human equivalent of the vitamin K dose given to the rats is in the range of 52,000 mcg (52mg) to 97,000 MCG) (97mg) per day. Also, in Japan, a 45,000 mcg (45mg) daily dose of the MK-4 form of vitamin K2 is approved as a drug to treat osteoporosis. Admittedly, these are high doses compared to the dietary industry standards. 

Consider a high quality MK-7 form of vitamin K2. And as they are inexpensive, include vitamin K1 and MK-4 to help inhibit and possibly reverse vascular calcification.

Although the exact dosage of vitamin K is yet to be determined, one of the world’s top vitamin K researchers, Dr. Cees Vermeer recommends between 45 mcg and 185 mcg daily for adults. (LifeExtension magazine recommends 200 mcg.)

Consider a high quality MK-7 form of vitamin K2. And since vitamin K1 and MK-4 are inexpensive, it makes sense to include them to inhibit and possibly reverse as much arterial calcification as possible. One product to look at is Life Extension Super K with Advanced K2 Complex Softgels, 90-Count available from Amazon.com

Balancing Vitamin K and Warfarin for Proper INR Ratio

People taking warfarin are often told to lower their intake of vitamin K foods like leafy greens, liver, etc., because they interfere with the anti-blood clotting effect of warfarin. Not true.

Prolific A-Fib blogger Dr John Mandrola (Dr. John M.), posted about misinformation surrounding warfarin patients and vitamin K. He wrote:

“I am so utterly tired of correcting this mistake….Patients on warfarin can indeed eat green vegetables; they should just eat them consistently. I have vegetarians who do beautifully on warfarin. The problem comes when people vary the weekly dose of vegetables.

So, if you and your doctor decide that you should take warfarin, take more vitamin K, not less! You can take vitamin K. The key is to be consistent on a daily schedule. If consumption of vitamin K does affect your INR, your doctor can always adjust the warfarin dosage.

Your Bottom Line Goal

If you continue to take warfarin, your goal is to maintain the highest healthy levels of vitamin K to counteract the effects of warfarin on your arterial and bone health.

If you change from warfarin to a NOAC, your goal is to restore your arterial and bone health from the effects of warfarin by maintaining the highest healthy levels of vitamin K.

References for this article

Stop Taking Warfarin―Produces Arterial Calcification

Stop Taking Warfarin―Produces Arterial Calcification

Warfarin - Coumadin tablets various dosages

Warfarin (brand name Coumadin) various dosages

The blood thinner, warfarin (Coumadin) is a “vitamin K-antagonist” which works by blocking vitamin K (i.e., K-2, menaquinone), thereby affecting several steps in the anticoagulation pathway and decreasing clotting proteins in the blood.

But vitamin K is also essential for heart and bone health. Vitamin K determines whether we maintain strong bone density and soft pliable tissues. Without enough K-2, osteocalcin, a protein that binds calcium to bone, doesn’t function. This vascular calcification produces plaque and reduces aortic and artery elasticity.

“When calcium doesn’t stay in bones, it can end up clogging your arteries, causing a heart attack or stroke.”

Vitamin K chemical structure

Vitamin K chemical structure

Warfarin Blocks Vitamin K: Deposits Calcium in Arteries

By blocking vitamin K (K-2), warfarin deposits calcium in our arteries and progressively turns them into stone. In the absence of vitamin K, bony structures form in soft tissues. When you hear the term “hardening of the arteries,” this means that previously flexible blood vessels are turning into rigid (calcified) bony structures.

In a study of 451 women using mammograms to measure arterial calcification, after just one month of warfarin use, arterial calcification increased by 50% compared to untreated women. After five years, arterial calcification increased almost 3-fold.

Why You Should You Stop Taking Warfarin

If you are taking warfarin (Coumadin), you should talk to your doctor about switching to Eliquis (apixaban) which tested the best of the NOACs and is the safest. (See my article, Warfarin and New Anticoagulants.)

NOACs anticoagulants on notepad 150 pix at 96 res

Eliquis (Apixaban) is one of the new NOACs

The new oral anticoagulants (NOACs) do not block vitamin K. But the NOACs do have drawbacks. In the case of severe bleeding, there is currently no antidote or reversal agent like there is for warfarin (a reversal agent for the direct factor Xa inhibitors Xarelto and Eliquis is close to FDA approval).

Added 2015: The FDA approved a reversal agent Praxbind for the NOAC Pradaxa Oct. 16, 2015. In clinical trials, 5gs of Praxbind (idarucizumab) administered by IV reversed the anticoagulant effect of Pradaxa within minutes (which is significantly faster than the current antidotes for warfarin).

Whether or not to be on an anticoagulant and which one to take is the most difficult decision you and your doctor have to make (and your initial decision may change over time as your body changes.)

If you aren’t happy with your doctor’s response, get a second opinion. You need to feel confident and at peace with this decision.

References for this article

FAQs A-Fib Drug Therapy: Vitamin K Foods and Bleeding Risks

 FAQs A-Fib Drug Therapy: Vitamin K Foods

Drug Therapies for Atrial Fibrillation, A-Fib, Afib11. “Do I need to avoid foods with Vitamin K?  I am on Coumadin (warfarin) to thin my blood and prevent A-Fib blood clots. Do I now need to avoid foods with Vitamin K which would interfere with the blood thinning effects of Coumadin?”

No, don’t avoid Vitamin K foods. Vitamin K is an important nutrient, especially for bone health and brain function. Vitamin K aids the metabolism and regulation of “sphingolipid” metabolism (Sphingolipids are fats that are a major component of brain cell membranes. They have a significant role in the structure and function of the nervous system.).

You should instead try to maintain a consistent intake of vitamin K through food and/or supplements. You should maintain at least the U.S. recommended amounts of Vitamin K (120 mcg/day for men, 90 mcg/day for women). 7

Your liver uses vitamin K to make blood clotting proteins. Warfarin lowers your risk of forming a blood clot by reducing the liver’s ability to use vitamin K to produce these blood clotting proteins. But you still need vitamin K for your overall good health. A lack of vitamin K, for example, can lead to osteoporosis. 8

Prolific A-Fib blogger, Dr John Mandrola (Dr. John M.), recently posted about misinformation surrounding warfarin patients and vitamin-K. He wrote:

“I am so utterly tired of correcting this mistake….Patients on warfarin can indeed eat green vegetables; they should just eat them consistently. I have vegetarians who do beautifully on warfarin.

The problem comes when people vary the weekly dose of vegetables.

Warfarin works by inhibiting vitamin K-dependent clotting factors. If one eats the same amount(dose) of vitamin K, the caregiver can easily adjust warfarin dose….This is not a nitpicky criticism; patients on warfarin have disease, and they should not be avoiding healthy plant-based foods.”

Let’s say you have low levels of vitamin K. If you then eat a spinach salad or liver which are high in vitamin K, this will cause a huge increase in vitamin K intake and consequently a significant drop in your INR (the amount of thinning of your blood). But if you consistently have normal (or preferably higher) levels of vitamin K, a spinach salad or liver will not cause a huge increase in vitamin K.

When starting Coumadin, you should talk over with your doctor how to maintain a consistent diet and/or supplement level of vitamin K. This is especially important if you change your diet. Ideally you should consult your doctor before making any major changes in your diet and vitamin K intake.

Thanks to Ruth McKee for the suggestion of this question.

Update 6/20/15: With the new anticoagulants (NOACs) now available, no one probably should be taking warfarin anymore. Warfarin produces arterial calcification, and also puts patients at increased risk of osteoporosis and bone fractures. (See Stop Taking Warfarin [Coumadin]!!! Switch to Eliquis [Apixaban].)

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