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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. I have severe osteoporosiss; because I work out daily (1hour and a half), the osteo is not visible. Now, I also have lupus. I do not have kidney problems and no hipatitis. Doctors do not say too much about vitamins or herbs. They told me to take calcium with D, but that is all. Would any other vitamin be beneficial for me? I eat the best food; not the most expensive food, but the best. Fresh vegetables, fruits, legums, etc.
    Thank you
    Marika Bodnar

    Marika Bodnar wrote on November 13th, 2011
    • Well Marika, if you believe the research, you should buy Vitamin K2 supplement(try it is not expensive. It is supposed to be vital in keeping the bones strong, working with vitamin D and calcium as a cofactor.
      Do you eat fermented cheeses like camembert, stilton, gouda, mature cheddar and curd cheese? They have lots of natural K2 made by the bacteria in the cheeses. I eat legumes too, but it won’t go down too well on a paleo website!…..and lots of grains, dairy and no meat…and feel in the best of health….better not go on!

      Chris Aylmer wrote on January 28th, 2013
    • Please check out Menacin for Vitamin D, Calcium and Vitamin K2. or visit the facebook group Menacin Natural Vitamin K2 Supplements 😉

      John wrote on February 24th, 2013
  2. Regarding the Weston Price link to the K2 content graph of foods, the link in the article did not work, but here’s a link that does work:

    Summer wrote on March 1st, 2012
  3. whaat about K3? will I need another pill?!?

    sprogy wrote on April 24th, 2012
  4. Can we consider Vit K4and Vit K7 have same function and same indication
    and as considered menaQ7 and mena K4 are both vit K2

    which you prefer
    and why
    Dr Samir

    Dr Samir wrote on May 4th, 2012
  5. Does anyone know where one could get a K2 supplement in the MK4 form?

    Mike wrote on July 19th, 2012
    • The only MK4 supplements that I know of to recommend, are green pasture’s butter oil, and Thorne’s K2 drops. Thorne also makes a D3/K2 combo.

      Pharmacist wrote on July 31st, 2012
  6. Have been Paleo for about 2 yrs. (got there on my own b/f knew about Paleo). I was so lean 2 months ago my blood vessels were much too prominent so I decided I needed more fat. About that time, I also discovered K2. With my osteoporosis worsening, I decided to add back raw grass-fed cheese for the fat and K2. My skin has filled out from the added fat and am hopeful the K2 will improve my bone density. Am concerned about the dairy though, but skeptical about adding natto due to lectins in the soybeans and feel the cheese is the lesser of two evils. Also, added a whole body vibration machine to my regimen for the bone density. Thoughts on natto? May try homemade sauerkraut for it’s K2.

    Vicki Carpenter wrote on October 25th, 2012
  7. I first learned about vitamin K2 in an Osteoporosis forum. Many on the forum take both forms of vitam K2, MK-4 and MK -7. I have been using MK-4 for a few weeks now for my bones and teeth. Funny thing is I notice that my skin has improved and the plaque on the underside of my bottom teeth is much less. I’m hoping it will help further with my teeth as I have suffered with periodontal disease for many years.

    I am on a modified Paleo diet. Grass fed products are not readily available where I live so I can’t eat totally that way plus I’m on a retired fixed income and it will only go so far. Therefore, I use some supplements.

    I’m 69 years old and still kicking and wanting to learn and improve my life. It’s never too late, right? The Paleo diet is the best one I’ve found to help me enjoy eating. I have Celiac disease and feel fortunate that Paleo is the perfect solution to my dietary needs. There are lots of good books and recipes out there. No need to feel deprived!

    Caroline wrote on December 6th, 2012
  8. How much K2 does natto contain ?

    Johan wrote on December 8th, 2012
  9. I seen the question about kidneys -if K2 is ok –I have stage 4 renal failure–on no meds anymore for my kidneys-been taking D3 for over 1yr an it made big difference–plus I did take antibiotics alot for kidney infections -so much that it has given me —slow gut snydrum–plus I had that plura infection of the gut (i know i spelled it wrong) the dr. put me on triple antibiotics–I took myself off an got on –DGL–&–MASTIC GUM—an got retested an it was all cleared up-I stopped after 1month on these an the belly pain came back in full force–that;s when they found the -slow-gut–so I put myself back on the mastic gum & DGL—after few days noticed big difference so I am taking them forever—I added K2 because I was getting alot of chest tightness -stress test came out ok-but yet they now say the stress test really doesn’t tell the right stuff for woman-because we have trouble with our smaller arteries –to where men have with the larger arteries an thats what shows up are the larger ones not the smaller–an I take 200mg a day of K2–an seem to be fine the chest stuff seems to stopped –I take it because it helps clear the calcium deposits out of the veins –smaller ones to an that was what I was worried about being a woman at age 58—I had a total hysto when I was 34yrs old an already went through menopause -I take no estrogen-so the K2 will benifit the bones—-but I need to know if the K2 will harm the kidneys? I felt safe to take it because I am not on any meds other than a blood-pressure pill an only 5mg at that–I didn’t take any but the BP started to get high 149/105—the top always higher so they put me on a small dose—now this was before I started K2–I’m waiting to see if the BP stays down I will slowly remove the BP med-an keep on the K2 -plus I have been on Vde 5000everday–seems the kidney eats up D3 the kidney drs had me on meds of D3-50,000 for months than I asked if I could take it as a vitamin instead of thier pill an I could so the 5,000 seems to keep my levels at a normal range—-if you could answer me –at my e-mail——-I thank you very much—-there is alot more health things if you like to know ask an I will fill you in on a more private e-mail—tksxo

    denise wise wrote on December 10th, 2012
    • Hi. I know this is an old post Just wondering how u got on with the k2. I am atage 3 ckd and from my research it seems k2 would be a good supplement to add.

      clare wrote on February 12th, 2015
  10. I read that k2 from Natto can dissolve calcifications. I have pain from calcification on the right shoulder bone and it’s tearing at the Tendon on the top of the shoulder. I’ve recently had surgery on the left shoulder to remove the calcification. HOW MUCH TIME does it take to start dissolvingcalcifications?

    Ginger wrote on December 28th, 2012
  11. I reently started taking K2 after finding out I have hypercalcemia which is not related to the parathyroid as my PTH came back normal from blood test.
    How much K2 should I take, I also have high blood pressure, taking lisinopril with water pill combination. I do not feel bad at this time, just worried about the calcium level in my blood which is above normal. i have an appt with an endocrin in April, HELP!

    Rana Franke wrote on January 17th, 2013
    • Hi Rana,
      The Dutch researchers recommend up to 180mcg K2 per day with a basic requirement of 45 mcg per day. The MenaQ7 that they use in their experiments is now formulated as a supplement capsule for humans containing 45mcg. The head researcher(forgotten his name) takes 180mcg per day. He also strongly recommends eating a little fermented cheese on a regular basis such as curd cheese or strong mature cheeses.
      Good luck

      Chris Aylmer wrote on January 28th, 2013
    • How have you felt after taking k2? I have high calcium, too, which is not PTH. What did the professional you saw say about this?

      Climber wrote on May 31st, 2015
  12. Makes me understand now why virtually all ancient cultures (and some still do) incorporated some kind of fermented or cultured food into their diet on a regular basis.

    Ali wrote on January 23rd, 2013
  13. 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
  14. 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
  15. 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
  16. 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

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