Food sources of vitamin K2: Reprint

For some reason, my December, 2007, Heart Scan Blog post, Food sources of vitamin K2, has been receiving a lot of traffic.

I therefore reprint the vitamin K2 post below.

Vitamin K2 is emerging as an exciting player in the control and possible regression of coronary atherosclerotic plaque. Only about 10% of dietary vitamin K intake is in the K2 form, the other 90% being the more common K1.

The ideal source of K2 is natto, the unpalatable, gooey, slimy mass of fermented soybeans that Japanese eat and has been held responsible for substantial decreases in osteoporosis and bone fractures of aging. Natto has an ammonia-like bouquet, in addition to its phlegmy consistency that makes it virtually inedible to anyone but native Japanese.

I say that the conversation on vitamin K2 is emerging because of a number of uncertainties: What form of vitamin K2 is best (so-called MK-4 vs. MK7 vs. MK-9, all of which vary in structure and duration of action in human blood)? What dose is required for bone benefits vs. other benefits outside of bone health? Why would humans have developed a need for a nutrient that is created through fermentation with only small quantities in meats and other non-fermented foods?

Much of the developing research on vit K2 is coming from the laboratories of Drs. Vermeer, Geleijnse, and Schurgers at the University of Maastricht in the Netherlands, along with several laboratories in Japan, the champions of K2.

MK-7 and MK-8,9,10 come from bacterial fermentation, whether in natto, cheese, or in your intestinal tract; MK-4 is naturally synthesized by animals from vitamin K1. While natto is the richest source of the MK-7 form, egg yolks and fermented cheeses are the richest sources of the MK-4 form.

Chicken contains about 8 mcg MK-4 per 3 1/2 oz serving; beef contains about 1 mcg. Egg yolks contain 31 mcg MK-4 per 3 1/2 oz serving (app. 6 raw yolks). Hard cheeses contain about 5 mcg MK-4 per 3 1/2 oz serving, about 70 mcg of MK-8,9; soft cheeses contain about 30% less. Natto contains about 1000 mcg of MK-7, 84 mcg MK-8, and no MK-4 per 3 1/2 oz serving.

Feta cheese

Thanks to the research efforts of the Dutch and Japanese groups, several phenomena surrounding vitamin K2 are clear, even well-established fact:

--Vitamin K2 supplementation (via frequent natto consumption or pharmaceutical doses of K2) substantially improves bone health. While K2 by itself exerts significant bone density/strength increasing properties in dozens of studies, when combined with other bone health-promoting agents (e.g., vitamin D3, prescription drugs like Fosamax and calcitonin), an exaggerated synergy of bone health-promoting effects develop.

--The MK-4 form of vitamin K2 is short-lived, lasting only 3-4 hours in the body. The MK-7 form, in contrast, the form in natto, lasts several days. MK-7 and MK-8-10 are extremely well absorbed, virtually complete.

--Bone health benefits have been shown for both the MK-7 and MK-4 forms.

--Coumadin (warfarin) blocks all forms of vitamin K.

Interestingly, farm-raised meats and eggs do not differ from factory farm-raised foods in K2 content. (But please do not regard this as an endorsement of factory farm foods.)

Another interesting fact: Since mammals synthesize a small quantity of Vit K2 forms from vitamin K1, then eating lots of green vegetables should provide substrate for some quantity of K2 conversion. However, work by Schurgers et al have shown that K1 absorption is poor, no more than 10%, but increases significantly when vegetables are eaten in the presence of oils. (Thus arguing that oils are meant to be part of the human diet. Does your olive oil or oil-based salad dressing represent fulfillment of some subconscious biologic imperative?)

If we believe the data of the Rotterdam Heart Study, then a threshold of 32.7 micrograms of K2 from cheese yields the reduction in cardiovascular events and aortic calcification.

It's all very, very interesting. My prediction is that abnormal (pathologic) calcium deposition will prove to be a basic process that parallels atherosclerotic plaque growth, and that manipulation of phenomena that impact on calcium depostion also impact on atherosclerotic plaque growth. Vitamins D3 and K2 provide potential potent means of at least partially normalizing these processes.

As the data matures, I am going to enjoy my gouda, Emmenthaler, Gruyere, and feta cheeses, along with a few egg yolks. I'm going to be certain to include healthy oils like olive and canola with my vegetables.

All images courtesy Wikipedia.

Copyright 2007 William Davis, MD

Comments (59) -

  • Chloe

    1/19/2010 3:11:02 AM |

    "Egg yolks contain 31 mcg MK-4 per 3 1/2 oz serving (app. 6 raw yolks)."

    Any data on the effect of cooking or methods of cooking that would affect the MK-4 in eggs?  Soft boiled, hard boiled, fried (I use coconut oil or butter)whole yolk like over easy, scrambled, in a quiche?  

    Any thoughts on other fermented foods and vitamin K--sauerkraut, kim chi, dill pickles?  

    And...I have the Thorne Vitamin K2 supplement that supplies vitamin K2 (menatetrenone) one drop equivalent to 1 mg (1250% %DV).  How number of drops daily?

    Thank you, Dr. Davis, for bumping this information to more current status.

  • Dexter

    1/19/2010 3:24:22 AM |

    Dr Davis,

    I have read on several blogs that
    canola oil...rapeseed one of the frankenfood oils to avoid
    along with corn oil, soybean oil,
    safflower oil because they are high in PUFA omega 6 and thus are pro inflamatory agents.
    Dr Kurt Harris at is one who has written to avoid canola as well as flaxseed oil.

  • Ed

    1/19/2010 3:26:55 AM |

    I thought bone marrow had k2 in it? If so, this would have been a very appealing source to primitive man.

  • Dexter

    1/19/2010 3:28:06 AM |

    Dr Davis,

    I was under the impression that canola oil as well as flaxseed oil
    is to be avoided because of the high PUFAs Omega 6 FA.

    Dr Kurt Harris at has written to avoid those oils high in O-6s.

  • Stan (Heretic)

    1/19/2010 3:30:21 AM |

    Another beneficial effect of K2 is reversal of tooth decay and self-healing of broken teeth.   This is based on my personal observations.

  • Hillary

    1/19/2010 4:17:06 AM |

    An interesting study was published within the past several years, by Chris Masterjohn.  His study was to identify the "activator X" factor reported by Dr Weston Price in the early 20th century as being found in the butterfat, organs and fat of animals feeding on rapidly growing green grass (i.e. in the spring).  "X" was also found in fish roe and perhaps other seafood.  

    Dr Price believed the vitamin-like 'activator X' was critical for the body's utilization of minerals, prevention of tooth decay, brain function, protection against heart disease and so on. He was never able to identify this factor but did concentrate butterfat (from (spring) grassfed cows) into a butter oil which he gave to patients in his studies on various health issues, with reportedly excellent results.  At least one company today sells butter oil produced from grassfed cows under the same conditions and I know several people who are convinced this has helped keep their families healthy.

    For more than 60 years no one knew what activator X actually was until Masterjohn investigated it in detail.  It is his belief that activator X is vitamin K2.  His study (with references)can be found at:


  • pmpctek

    1/19/2010 4:23:45 AM |

    Don't forget butter fat is another very good source of vitamin K2 MK-4.

    Weston Price would argue that dairy fat and eggs from farm raised animals fed (K1 rich) fast-growing grass do have a higher K2 content when compared to grain-fed factory raised animals.  Much of modern animal feeds have high amounts of menadione (a K3 supplement) but the animal's ability to synthesis this to K2 is unknown.

    Price's analysis also showed that  a human intestine's ability to synthesis K1 to K2 is much less efficient compared to that of a ruminant's intestine.  I guess that also kind of explains why humans wouldn't do as well on a diet solely consisting of grass as that of a cow.

  • Anonymous

    1/19/2010 4:35:50 AM |

    DH tried natto because he's intolerant of eggs, casein and a few other foods. He didn't care for it. How many servings of chicken does he need in a week? Would chicken broth have any?

  • LeenaS

    1/19/2010 5:55:08 AM |

    You did not mention butter as a decent K2-MK4 source. Why?

    Butter and cream are our greatest sources of K2, next to egg yolks.

    Thanks for the blog and regards,

  • Vladimir

    1/19/2010 6:10:31 AM |

    Do you think it would be a good idea to take Vitamin K2 supplements?  Life Extension has one with 1mg MK-4, 100 mcg MK-7, and 1mg Vitamin K1.  Good idea, or premature?

  • Dr. William Davis

    1/19/2010 1:27:43 PM |

    I believe that the data on K2 are compelling. Does K2 supplementation , or at least weighing diet in favor of K2-containing foods, reduce cardiovascular risk or provide better atherosclerotic plaque control? While the circumstantial evidence suggests it will, we still lack the K2 vs. placebo trial that would prove the concept. Nonetheless, because of the data on bone health (which is quite confident), I personally believe there's nothing to lose. I personally supplement 1000 mcg per day.

  • Dr. William Davis

    1/19/2010 1:28:47 PM |

    Pmp and Leena--

    Thanks for reminding me about the butter.

  • Anonymous

    1/19/2010 2:51:58 PM |

    Observational studies have linked low intakes of vitamin K with osteoarthritis. No research yet as to whether this vitamin can be used to treat that disease, but I think there is some promise there. More natto, eggs, and leafy green veggies for me.

  • Phil

    1/19/2010 3:02:56 PM |

    Dr Davis,

    So glad to see your posting on Natto. Could please elaborate on the desirability of consumption of Natto by people who are on Warfarin therapy? You mention that Coumadin blocks all forms of Vit-K and I seem to have read that taking K2 while being on Warfarin is okay. Any pointers to published literature is welcome!


  • TheOtherKim

    1/19/2010 6:11:29 PM |

    I'll second Dexter's question.  I too, was under the impression that canola oil was not a "healthy" fat.

  • Jim

    1/19/2010 6:37:35 PM |

    Another Weston A Price article written by Chris Masterjohn is at

    Note the C(ancer) word in the link.

  • Katie

    1/20/2010 12:08:00 AM |

    Dr. Davis, I am heterozygous for Factor V Leiden.  I'm not on any anticoagulants, such as warfarin, and have not had any complications.  I am really interested in K2 supplementation because it seems to have so many health benefits, but have been nervous because of my blood clotting condition.  Do you know if K2 supplementation is safe in someone with one Factor V Leiden gene mutation?

  • Coach Jeff

    1/20/2010 3:05:30 AM |

    Could the atherosclerotic plaque found in Egyptian Mummies possibly have been a mere vitamin-k deficiency? I just never bought the theory that it was totally caused by their grain consumption.

  • Anonymous

    1/20/2010 3:21:08 PM |

    I am on warfarin since December for AFib/flutter which is OK now with sotalol.   I told the cardiologist I didn't like taking warfarin since it destroyed vit K.  He said no, it was the other way around, vit K destroys warfarin, and said "we want you to take vit K".  My INR stays low and they keep increasing the dose.   I believe that warfarin is a vit K antagonist, the more I take the more it will destroy the vit K.  

    I can feel it when I am arrhythmic, I weigh 115 lbs, am 62, female and have a low CHADS score, some borderline HBP for which I take norvasc. 15 years ago I had mitral valve repair for a flail leaflet.  How much should I argue with him?   I already have osteopenia.

  • cete

    1/21/2010 4:50:19 AM |

    There was a study on low dose warfarin after coronary artery bypass to see if it helped prevent graft occlusion. It didn't. What they did find was a reduction in mortality after bypass with the warfarin, of about 30%. What I wonder is if adding more vitamin K as a supplement will make you more prone to clot. I worry that this could be a case where there is less calcium, but more clotting in the arteries with the extra vitamin k as one of those unintended consequences.

    I would like to here your thoughts about this.

  • Dr. William Davis

    1/21/2010 12:02:04 PM |

    Provided you are not taking warfarin (Coumadin), vitamin K2 supplementation or eating foods rich in K2 should NOT make your blood clot any more than normal.

    I tell my patients that taking vitamin K2 is no more likely to make your blood clot than filling your gas tank to the top makes your car go faster.

  • natto freak

    1/21/2010 4:50:04 PM |

    I just love my Natto and vitamin K2 supplement. Nothing clears my brain fog like Natto.

  • cete

    1/22/2010 4:59:28 AM |

    Dr. Davis,

    Thanks for your answer. I take a lot supplements and over the years have added and dropped some due to changes in information about efficacy and safety. With my terribly high calcium score, 686- I have familial hypercholesterolemia, I have been interested in the Vitamin K2 supplements. What has held me back is the question of safety. Over the years some of trials of supplementation with vitamins and other natural compounds that seemed to make sense didn't turn out well clinically. Specifically, I was thinking of the failure of benefit from folic acid supplementation for elevated homocysteine and the problems associated with beta carotene in smokers.

    Perhaps it is time now for me to give the Vitamin K2 a try.

  • David Moss

    1/22/2010 9:29:09 PM |

    Great post, I'm always after information on K2 (although I read the article in its original form too!).

    Anyway I was interested to see feta in your list and photographed... I thought that feta being a basically unmatured cheese would be quite low (I used to eat tonnes of 18month-5 year matured cows cheese before I switched only to goat/sheep dairy, so I'd be interested if it was worthwhile eating feta for K2.

    I always wondered how much the amounts cited for "hard cheese" varied from cheese to cheese, and how much was from fermentation and how much from cheese being 80% butter.

  • Anonymous

    1/24/2010 6:35:38 PM |

    back in 2002, I had an angiogram due to a series of waring signals and family history. Turns out I had two blockages but somehow my heart had built its own pathways around hence no heat attack. The Surgeon said, he couldn't do much and I needed to get on medication as soon as possible. I won't bother with details but I did slowly make progress to be able to cycle and walk long distances but I always had jaw ache and tightness in my chest just after starting any exercise. I would stop catch my breath, wait for the pain to subside and neither symptom would show again until I went through a rest period.

    In Canada the max allowed K2 dose  is 120mcg. Having looked at the various studies, and mechanisms, I decided K2 was my best bet to see some improvement. I was taking 6 capsules of 120mcg MK4 per day. I felt a whole lot better. So, on a trip to the States, I purchased Life Extension "Super K" which is 1000mcg or 1grm of MK4 and mega-dosed for 6 weeks on 6grm/day.  I am back down to one capsule now but I no longer get ANY angina on changes to intensity of exercise. I played soccer in the summer. I even went Jogging in the first part of winter without any issues (heart at least, my lungs are way out of shape!)

    Is K2 in high dose safe? I have no idea, but I feel it has worked for me and like so many life style choices, that is a big element in one's well-being.

  • livesimply

    1/25/2010 2:29:26 AM |

    I am hypothyroid and avoid all soy; also gluten and casein sensitive so avoid gluten foods and dairy.  I do eat whole eggs regularly and leafy greens with hi-oleic safflower oil or avocado oil.  And since butter is mostly fat and very little casein I do have a fair amount of that, too.  Smile

    Should I therefore avoid the natto (soy) form of K2 and stick with MK-4 or MK-8?  

    Thanks--very interesting topic.

  • Term Papers

    1/29/2010 7:55:51 AM |

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  • Anonymous

    2/22/2010 4:36:52 PM |

    Great post, first of all!!!

    Second of all, I have a comment on this part of your post:

    "--The MK-4 form of vitamin K2 is short-lived, lasting only 3-4 hours in the body. The MK-7 form, in contrast, the form in natto, lasts several days. MK-7 and MK-8-10 are extremely well absorbed, virtually complete. "

    While this is true, it tells us nothing about which form is better for human physiology.  Although MK-4 disappears from the bloodstream rapidly, that could either be a good or bad thing.

    On the one hand, this could indicate that MK-4 is rapidly taken up by cells, and thus has a greater physiological absorption than MK-7.  MK-7 hangs around much longer in the bloodstream, but this could very well mean that MK-7 is NOT used by human cells very well.

    On the other hand, it could be that MK-4 is being rapidly removed and excreted from the bloodstream.

    I suspect that the more likely scenario is the first, because the human body does not produce any MK-7 at all.  If you consume MK-1 (phylloquninone) the human body will process some of this into MK-4.  If you take human tissues samples, you will find ONLY MK-4.... no MK-7 or MK-9 at all.

    MK-4 is what mammals produce naturally, so it is likely the most physiologically active.

    Just a comment.


  • chave

    3/3/2010 6:14:59 PM |

    Hi Dr. Davis
    I've been very interested in the Japanese and their lower postmenopausal hip fracture and heart disease rates.  I'm probably one of the people who added to the traffic on your K2 info.

    What also interests me is that the Japanese (and most Asians in general) traditionally use very little in the way of milk products too.  They have low fracture rate and low BMD, interestingly.  They only consume about 500mg of calcium per day mostly through vegetable sources.

    I have a study that rated the relative importance of K, magnesium, Vitamin d and calcium in relation to fractures and calcium had the lowest association if any at all.  Vitamin K was strongly associated.

    Ecological studies show that cultures that consume less milk have lower fracture rates and that as they consume more milk their rates go up.

    Also, I've been reading a bit on the so-called bone-vascular axis and how there might be a connection between osteoporosis and vascular calcification.

    Is it possible that the recommendation to consume 3 daily helpings of dairy and supplemental calcium is contributing to the much higher fracture rate and heart disease in the West?

  • Cris P (Alonzo Neighbor)

    4/6/2010 6:30:10 PM |

    Dr Davis - like a previous poster, I have a factor V (Leiden) heterozygosity. I am currently taking a D3 tab with K2 several times a day for bone health as I now have ostopenia in my neck and osteoporosis in my spine.  I have previously had a TIA and am concerned about another or a full-blown stroke.  After my TIA, my cardiologist found a PFO, which further complicates things.  Is it safe for me to take up to 1,000 mcg of K2 daily?  Thanks

  • sammy

    4/9/2010 2:16:07 PM |

    If you’re looking for a supplement to assist in bone health, consider VitaNat Natural Natto Vitamin K2. This takes natto, the Japanese superfood known for being nature’s richest source of Vitamin K, and puts it into capsules. No extracts, no vitamin supplements, just Natto blended to a standard strength of Vitamin K2. Vitamin K2 is recognised for its role in maintaining good bone health, for more information look up

  • Anonymous

    5/12/2010 12:17:12 AM |

    Canola oil is not 'healthy'.  It is processed and most likely GMO.  The industry promoted it as health... Go with Coconut Oil instead! Cheers! Smile

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    6/9/2010 10:58:46 AM |

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    9/18/2010 2:50:50 AM |

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  • Shane Boulton

    9/20/2010 12:13:23 PM |

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    Essay | Admission Essay

  • Anna Delin

    10/4/2010 8:21:07 PM |

    I would add fermented (lactic acid bacteria) herring as a potentially vitamin K2 rich food. This food is traditionally eaten in August in north Sweden. It has a horrible smell (H2S), but the taste reminds me of well matured cheese (think rural France).

  • buy jeans

    11/3/2010 9:08:48 PM |

    Much of the developing research on vit K2 is coming from the laboratories of Drs. Vermeer, Geleijnse, and Schurgers at the University of Maastricht in the Netherlands, along with several laboratories in Japan, the champions of K2.

  • Richard the Foolhardy

    12/23/2010 7:05:29 PM |

    What labs can, or where/how can I, do a test for vitamin K2 level in the blood, preferrably with a report that distinguishes between MK-4 and MK-7?

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  • Janet

    7/6/2011 1:32:11 PM |

    Can anyone tell me where I might find Natto minus MSG?

    Thanks a bunch.

  • daniel ketchum

    7/13/2011 5:20:47 AM |

    Ok so k2 is produced by bacterial fermentation but of what nutrient? i have not been able to find any info on what nutrient the bacteria converts into k2 is it k1? or something else.. if its k1 then wouldn't fermentation of foods high in k1 produce the most k2? If so then is Natto loaded with k1?  Just curious because i just tarted making my own sauerkraut and lacto fermented vegetable juice...Have never even tasted Natto but i am going try it and if i like it well ill just have to start making that to...been making homemade curds and whey for awhile now and that should be a good source to. Also it seems that some of the fermented foods that have the most k2 (Natto, sauerkraut) in them are also very high in PQQ which is awesome!!!

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    7/22/2011 12:56:38 AM |

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  • Alfina

    10/14/2011 12:04:16 AM |

    Found your question why googling K2 when testing positive for Factor V.  I wanted to begin taking vitamin K2 to help in the calcium buildup in my arteries but now found about about Factor V and cannot seem to find information online. Have you received a reply to this question from 2010?

  • GB

    11/18/2011 4:15:34 PM |

    A question: If you take a look (google them) at several websites (such as whfoods) where they look at foods that contain the vitamin K, it seems that whole foods such as Kale along with other leafy greens provide a huge amount of vitamin K - I was surprised to see that this was not mentioned among the various comments - rather supplements are mentioned first and foremost – is this because the Vitamin K and the Vitamin K2 are different? - doesn’t one come from the other? Can someone explain this as I will always try to do through diet first before resorting to supplements?

  • Dr. William Davis

    11/20/2011 3:59:11 PM |

    Yes, two different nutrients.

    K1 comes from green vegetables, K2 does not.