Marks Daily Apple
Serving up health and fitness insights (daily, of course) with a side of irreverence.
23 Feb

Dear Mark: Vitamin K2

Dear Mark,

I’ve been hearing a lot about vitamin K2 lately. Should I be taking vitamin K2 supplements or is a Primal diet sufficient?


Thank you, Kate, for the question.

You find it in politics, fashion, entertainment, art, even cooking: the “it” figure, new notable, celebrity du jour. As odd as it is, the seemingly humble world of micronutrients isn’t immune from spotlight blitz. Some vitamin or mineral, subject of a timely string of studies, gets thrust into the limelight, and the medical media jumps on the news. Sometimes the hoopla is warranted. Oftentimes, it’s overblown. Most of the time, it’s here today gone tomorrow. Such an odd frame for public health education, I think – and likely the reason many people shut out such reports all together. One day, it’s a miracle nutrient. The next, it’s torn down as “not all that.” Recently, vitamin D has been the one to adorn the marquis. But there’s another novel nutrient chasing its heels: the nebulous, little known vitamin K2.

“K2? Vitamin K. Hmmm. Don’t recall much about that from high school nutrition class. Isn’t it in, like, spinach and stuff?” “Vitamin K. Oh, yes, I think our kids got vitamin K shots right after birth. Was that vitamin K2?” Well, yes to the first, and “close but no cigar for the second.” (That would’ve been vitamin K1.)

So, what’s the deal behind the buzz anyway?

Here’s the story. First, the breakdown. Vitamin K: fat-soluble vitamin – or group of vitamins otherwise known as the naphthoquinones (K1, K2, K3). Call vitamin K1 (phylloquinone) the plant party of the bunch. The spinach association? That would be a source of vitamin K1. Some other K-friendly choices (kale, spinach, Swiss chard, mustard greens, parsley, broccoli, Brussels sprouts, asparagus and avocado) serve up a decent helping. Incidentally, the body can “make” K2 from K1, but it’s not a 1:1 conversion. Though many sources put it at 10:1, the presence of fat (oh, lovely, lovable fat) enhances that conversion process. Finally, vitamin K3 (menadione) is a synthetic version of the vitamin that has limited place in certain medical treatments but is generally considered unsafe and unnecessary for general use.

Vitamin K2 (menaquinone), the nutrient of the hour, has an interesting background. It’s the product of fermentation and usually of intestinal bacteria – either human or animal. Good sources? Meats and dairy products from pasture-raised animals – especially butter and organ meats, aged and curd cheeses, as well as fish eggs. Nonetheless, the much touted mega-source of K2 is natto, a traditional fermented Japanese dish consisting of sticky soy beans that offers a powerful nutritional punch but a rather limited flavor appeal to outsiders.

(As an aside (for those interested), the picture gets more detailed. Within the vitamin K-club, K2 fans out further into various forms (referred to as MK-n), the most talked about of which are MK-7 and MK-4. MK 8-10 forms exist as well. The MK-7 form of vitamin K2, the form that natto champions, lasts a number of days in the body, but MK-4, a shorter span form, comes with the more readily available [and widely eaten] eggs, pasture-raised meats, aged cheeses, etc. Grok is salivating as I type.)

So, what’s the big deal with this nutrient? The full compilation of recent research underscores the idea that K1 and K2 should be appreciated as separate nutrients with distinct physiological actions and benefits. K1, the more familiar vitamin, is known for its key role in directing blood-clotting in the body. (A K1 shot at birth – or series of drops in the first few weeks of life – are common practice in many countries to curtail hemorrhage incidents in newborns.) It also shows anti-inflammatory properties.

The picture for K2 seems to be a bit more varied. K2 appears to be especially key in maintaining bone mineralization and limiting the formation and lifespan of osteoclasts, cells which break down bone. Researchers are increasingly optimistic about K2’s potential for those with or at risk for osteoporosis but are looking to further studies to confirm this association. (Incidentally, K1 alone has not shown the same effectiveness for those with osteoporosis.) In the meantime, other research suggests that K2 may aid cardiovascular health as well by helping prevent or even reverse arterial calcification, a known contributor to cardiovascular disease. But that’s not all. Researchers are also looking at K2 (specifically MK-4) as a therapy for rheumatoid arthritis. And, wait, there’s more! Researchers are also examining the potential of K2 in the prevention of prostate cancer and in the complementary treatment of leukemia and lung cancer.

“But if it’s such a wonder nutrient, why doesn’t it lace a quarter of grocery store products like omega-3s seem to now?” (Oh, there’s a whole other ball of wax.) Besides being a little understood nutrient, the (legitimate) concern has been that many people are on anti-coagulants like Coumadin/warfarin. In fact, they’re generally in need of it, since Coumadin is a vitamin K antagonist. The worry isn’t so much that these people intake vitamin K (especially K2) within their normal diets but that they maintain a consistent dietary measure of it to allow for stable dosing of their anti-coagulant meds. (A complex dance, to be sure.) But I’d suggest that there are other increasingly common medications (digestive related prescriptions and antibiotics) that can limit the absorption of K and alter the body’s ability to naturally convert K1 to K2. Hmmm.

The fact is, for a healthy person not on medications, adequate vitamin K2 is easy to get from the Primal eating plan. Although an RDA for K2 hasn’t been established, Dietary Reference Intakes for vitamin K1 suggest between 90-120 µg/day. (I’ll be on the lookout for updates on K2 doses, but I’ll note that toxicity doesn’t appear to be a problem with vitamin K, and no UL (Tolerable Upper Intake Level) has been established.)

So, how do we get there (and ensure a little extra for good measure)? Undoubtedly, natto has its claim to fame, and kudos to the beans and all who eat them. However, the long-term benefits of (and need for) K2 was undoubtedly relevant to Groks all over the world. A good Primal eating plan (with or without the addition of natto) provides what Grok and we moderns need: grass-fed and rich organ meats, unapologetic egg yolks, ample veggies and greens (with plenty of fresh oils and pasture-raised butter fat, of course!), and – for those who enjoy them – grass-fed cheeses. For specifics, check out a K2 content graph from the Weston Price Foundation.

And that brings us back to the celeb-factor. Sure, we live a very different life from our ancestors: pollution, stress, longer life spans in some cases, etc. Some things we can’t change, but other things we can. A good Primal eating plan that serves up a wide array of nutrients – in the way Grok and his folk ate them (fat, protein, fat) – makes good plain sense. Our current society with its painfully limited and drastically skewed nutritional practices will naturally hit up against deficiencies – both relative and extreme. Add to this the nutritionally depleting cocktails of digestive and antibiotic prescriptions so many people are on these days, and you’ve made several million borderline cases inevitably bad. The result: a good faith but ultimately misguided, “miss the forest through the trees” mentality of “limelight” nutrition. (“K2 to the rescue!”)

Is vitamin K2 an overlooked, underappreciated nutrient that can offer substantial benefits? I believe absolutely yes, and I’ll look forward to reading more studies (and even the popular media reports) in the coming months/years. I love that K2 may serve as an effective and natural supplemental therapy for those with certain medical conditions. Also, for those on digestive or antibiotic prescriptions, the news offers sound advice to see your doctor about getting levels checked and considering supplementation. But what about the rest of us? What are we to garner from the research, the spotlight, the scientific scuttlebutt?  Consider the take home message on K2 as this. Good science has uncovered the fact that K2 is part of good, necessary nutrition. But good nutrition – from a dinner plate or a quality supplement (or both) – isn’t a matter of star performance but of solid ensemble rapport. (And, how could we resist? Yet another reason to go PB.)

Questions, comments, additions, discussion? Let me know your thoughts.

yamada3 Flickr Photo (CC)

Further Reading:

Grok Didn’t Take Supplement So Why Should I?

Scrutinizing Soy

Previous MDA Coverage of K2

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Imagine you’re George Clooney. Take a moment to admire your grooming and wit. Okay, now imagine someone walks up to you and asks, “What’s your name?” You say, “I’m George Clooney.” Or maybe you say, “I’m the Clooninator!” You don’t say “I’m George of George Clooney Sells Movies Blog” and you certainly don’t say, “I’m Clooney Weight Loss Plan”. So while spam is technically meat, it ain’t anywhere near Primal. Please nickname yourself something your friends would call you.

  1. Good article on K2 Mark.
    I am wondering about the conversion of K1 to K2. I listened to a lengthy interview given by the Dutch researcher from Utrecht with Dr Mercola. According to the Dutch researchers, there is plenty of K2 made in the human large intestine by bacteria but only a negligible amount is absorbed into the body. It almost all passes out in the faeces. They say that is why animals often eat their own faeces, like rats and rabbits…to get the vitamin K2 and other digested or fermented nutrients.
    They also say that the conversion of K1 to K2 in the human plasma and cells is very poor, inadequate and unreliable. K2 is readily absorbed however from the small intestine if it is in the food eaten, such as fermented cheese or natto or maybe pasture fed beef etc. How about the K2 produced in cows from their internal bacteria…how does that get into the meat? Is it better absorbed or do they convert the K1 to K2 in their bodies better than humans? Or is the theory that humans cannot adequately convert K1 to K2 wrong? If cows get K1 and K2 from eating grass, why can’t we get it from eating vegetables? These questions were not adequately addressed in the interview.
    I agree that there is a lot of hype and everybody is looking for the next wonder nutrient, superfruit and basically a panacea for all ills! Fashion has taken over. Fiber was the first big thing in the 1960s but you hardly ever hear it mentioned now. Even Atkins is definitely old hat, bless his soul. Every eating fad eventually outstays its welcome I guess and needs to be reinvented.

    All best

    Chris Aylmer wrote on January 28th, 2013
  2. Dear All, I buy the Vitamin K2 product named Menacin on
    It is very important to understand that Vitamin K2 in most cases should be taken with Vitamin D. For those interested there is a facebook group named Menacin Natural Vitamin K2 supplements!


    John wrote on February 24th, 2013
  3. Hey Mark if fermented foods are a great source of K’s then how about Kimchi, fermented cabbage. Or Kambucha, the health drink that is naturally fermented?

    Brent wrote on June 21st, 2013
  4. WHY are there no answers to most of the questions above?? I’m struggling right now and feel like I”m between a rock and a hard place~ Found this site and am really interested in finding out more about K2. I was diagnosed with anti-cardiolipin disease, where my blood produces and antibody that makes my blood clot abnormally. It’s not the same thing as “sticky” blood. But I’ve got several lesions in my brain from these small clots. They put me on Coumadin, but had several nose bleeds that were difficult to stop, so they took me off and put me on aspirin therapy with the advice to stay away from too much Vit K, such as spinach, kale, etc. I am a woman that also worries about osteoporosis and couldn’t take the normal protocols because of jaw issues. I do take Vit D, but do not take dairy of any kind. Any time I start a calcium supplement, I get a kidney stone so I try to stay away from that. I’d love more answers but feel I’ve fallen in to a deep abyss and can’t find my way out~

    Shay wrote on September 9th, 2013
  5. Hi , I’m trying to help my mother as she has Harderning of the arteries, and takes a blood thiner, Aspirin 100mg or Cardia .
    She also takes Duride 60mg , Lipitor 40mg , Zoton 30mg , Ezetrol 10mg.

    Over the passed 4 weeks ive given her 5,ooo iu of Vitamin D3. Yesterday I stoped giving it to her in fear that ,she will recive to much calcium in her arteries.

    I wanted to put her back on D3 in combo with K2, but , Ive also read not to give her K2 because it will interfear with the blood thinner.

    I am in need of help to weather she can take K2 , with this type of disease. PLEASE HELP ME HELP HER…..Lisa

    lisa west wrote on July 24th, 2014
    • Hi Lisa,
      You probably found an answer since you posted this a while ago.

      But I found this article, which not only states that K2 should be taken with D3, it also states that K1 can affect blood thinners like Coumadin….but K2 does NOT.

      If this article is incorrect i hope someone else will reply as I too am starting my Dad on the D3/K2 supplements…& he is on Coumadin.

      Brenda Scott wrote on March 22nd, 2015
  6. have high PTH levels and calcium in blood. would K2 help lower level.

    alma whalen wrote on April 14th, 2015
  7. I am 64 and was diagnosed with rheumatoid arthritis in 2010. I had thyroid cancer in 2007 which resulted in total removal of my thyroid. In the past four years, I have broken four bones, upper rt arm break, lower left leg break, rt wrist and the last one was my left wrist (one wrist bone broke and one of the long bones in my arm split). Surgery was required on both wrist breaks. My orthopedist said it was a difficult surgery due to the weakened condition of my bones. My rheumatologist recommended Forteo. However, my endocrinologist said I was unable to take it due to parathyroid test results (90 – 165). I currently take Areva daily, one Vit D 50,000 mcg monthly,one Enbrel injection weekly, two Cymbalta 60 mg daily, Synthroid 250 mcg daily and Calcium Citrate 3000 mg daily. From doing research on Vit K2, I believe it would help my bone density and strength. I am unsure as to the amount of Vit K2, which supplements and dosages I should take.I read that the Vit K2 and supplements should be taken at the same time with antidepressant medication (Cymbalta). Is this correct? I would appreciate any answers and advice concerning Vit K2 and its benefits for me.

    thank you,
    Mary Duduit

    mary duduit wrote on April 14th, 2015
  8. Greetings from pharmchris pharmaceutical, there is a product we need from you, but will like to know if you ship international and will also like to know if you accept credit card. We await your reply as soon as possible so we can send our product list to you, thanks
    Dr Chris

    .Dr chris wrote on August 2nd, 2015
  9. Far too little attention is being placed on the huge role that vitamin K2 plays in dental health. Many people are needlessly suffering costly dental problems due to an undiagnosed vitamin K2 deficiency. Modern diets are nearly always deficient in vitamin K2. Sadly most drug stores do not carry vitamin K2 supplements although many health food stores do.
    Don’t expect the American Dental Association to ever acknowledge the huge role of vitamin K2 with respect to dental health. There is way too much money being made off of crowns, root canals, implants, and costly oral surgery to repair damaged gum tissue.
    Mainstream dentistry has ignored research done way back in the 1920s and 1930s regarding vitamin K2 and the huge role it plays in determining caries susceptibility. It was called “Activator X” back in those days. Ramiel Nagel has websites that are spreading this type of information.

    Kelly Clover wrote on August 20th, 2015

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