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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You want comments? We got comments:

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. Thank you for the explanation! I now know why the Damage Control Master Formula doesn’t have any vitamin k in it!

    Holly wrote on February 23rd, 2009
  2. (oh, lovely, lovable fat)

    That’s funny!

    JD wrote on February 23rd, 2009
  3. Thanks for the post today. I learned a lot, as always. I’m always impressed by the detail you provide in each post. At least if I hear the “buzz” about Vitamin K2, I’ll know where I heard it first and be more informed.

    Conny wrote on February 23rd, 2009
  4. Wow… that is everything I needed and didn’t need to know about vitamin k. Thank you for all the info Mark!

    The SoG

    Son of Grok wrote on February 23rd, 2009
  5. The best article on K2 on the internet…I recommend everybody read it:

    More good reading here:

    Mosh wrote on February 23rd, 2009
    • It looks like that article is no longer there–the first one.

      Janet wrote on April 19th, 2015
  6. Mark,

    Like to see your take on B vitamins and the absolute waste of them in drinks these days…since the majority of them just end up going through and never being used if you catch my drift.

    Zen Frittata wrote on February 23rd, 2009
  7. Didn’t know about that. But I guess that’s why I’m on here, Mark :)

    Hm, seems vultures get a good portion of K2, no? Eating fermented dead animal and such… Speaking of fermented – the English lords and ladies are said to have a taste for fermented game. And, the french love their stinky cheese.

    Now we know WHY.

    It’s all about vit K2.

    I knew those rich b******s were onto something LOL!


    Yavor Marichkov wrote on February 24th, 2009
  8. Mark,

    I’m one of the rare westerners that LOVES natto.
    I stopped eating it over the past 3 years because of primal/EF life style.
    Is it ok to eat you think even though it’s soy?
    Eat as a treat every now and than perhaps? Or just a no-no?
    Thanks once again for the informative post.


    Marc Feel Good Eating wrote on February 24th, 2009
    • Soy is one of those few earth-foods that I would not recomend. Us women should stay away from soy, and genetically engineered, or unorganic soy is a big no-no to us all, but I believe guys dont have to worry about it as much.
      Fermented soy is much different, though, and highly nutritious, but until further studies come through about fermented soy, I would stick mostly to other fermented foods.
      But natto, unlike tofu or tempeh, is hardly like “soy” at all! It is concidered by trusted natural health gurus to be one of the healthiest foods on the planet. That difference? I’m not sure. Is it fermented longer? In a different way? Still not sure.

      Valary-Mac wrote on March 28th, 2011
  9. Very Interesting! I’d never thought about vitamin K2,really learned so much from this post.

    Great question Kate!

    Donna wrote on February 24th, 2009
  10. One of Stephan’s K2 posts at Whole Health Source was linked above, but he has several others as well as peripheral stuff on it.

    They can all be located here:

    Because of Stephan’s work here, I read also that Chris Masterjohn piece at the WAPF site, then read most of Nutrition and Physical Degeneration, probably the most important book on nutrition I’ve ever read. Price studied a bunch of non-industrial cultures in the 20’s and 30’s and documented their excellent dental and general health (they didn’t brush, floss, or have dentists, either).

    I’ve been on K2 (MK-4, the kind made from K1 by mammals, for other mammals — as Stephan puts it) supplementation for maybe six months now. I’ve posted some of my experiences with it:

    In general, plaque dissolved on my teeth within a few days and has never returned. I used to have to have cleanings 4 times per year to remove huge plaque buildup. A Paleo diet improved that a lot, and K2 has rendered it a non-issue; so much so that I don’t even brush my teeth every day anymore. I wake up and they are always pearly smooth.

    If you’ve ever been on an antibiotic like tetracycline, you may have noticed how soft it makes your skin. Same result with K2, virtually over night.

    Within about 3 months, the strength of my fingernails have at least doubled. They are actually highly useful tools, now. Very functional, and they never break. I’m sure Grok put his fingernails to good use every day.

    Richard Nikoley wrote on February 24th, 2009
  11. Animal foods really aren’t a very good source of K2, except for hard cheeses that have been fermented by bacteria, especially Swiss-type cheeses that have been fermented with by a specific type of bacteria called propionobacteria).

    Walter Pittman wrote on February 27th, 2009
  12. More K2 news:

    Vitamin K2 and Massive Reduction in Heart Disease: Leading Edge

    (And absolutely: MDA is certainly one of those places I mention while on the soapbox). Mark Sisson rocks!

    Richard Nikoley wrote on March 4th, 2009
  13. Walter Pittman: what about cheddar cheese? This is expensive but good stuff:

    Ed wrote on March 6th, 2009
  14. Great summary about vitamin k2, I appreciate this thoughtful post. However, your comment that humans NEED to eat meat, is false. Humans can be healthy eating meat, but they can also be healthy not eating meat. If there is ever any doubt just go to and see for yourself.

    casey wrote on June 8th, 2010
  15. That link to the K graph on the WAPF site is broken.

    Rabbi HIrsch Meisels wrote on October 21st, 2010
  16. I am a coumadine patient and am curious of the effects of K2 on the INR that I work so hard to maintain.

    darren wrote on October 27th, 2010
  17. A cardiologist told me last week that K-2 was potassium. Is that so?

    Robert wrote on October 28th, 2010
    • THAT made me smile…

      I’d love to meet that cardiologist.

      Primal Palate wrote on May 22nd, 2011
    • I asked our pharmacist about K2 and he said it was Potassium. Guess he and the cardiologist make a fine pair. Am going to ask my doctor about K2 as I cannot take osteoporosis medication of any kind.

      Donna wrote on May 9th, 2012
    • Vitamin K2 is something totally different from Potassium the chemical letter for Potassium is K. Tell your cardiologist to go back to basic chemistry class.

      Karola Behringer wrote on July 4th, 2012
  18. Robert, that’s hilarious. The symbol for potassium in chemistry is “K”, which I guess is what confused your cardiologist.

    Eric W. wrote on November 17th, 2010
    • Makes sense. Many thanks.

      Robert wrote on November 18th, 2010
  19. is k2 safe to take with other medications such as for type 2 diabetes, depression and PILL FOR KIDNEY FUNCTION?

    jane wrote on January 8th, 2011
  20. The problem is that other than studies conducted at the University Medical Center in Utrecht, The Netherlands, I can find no study (including those you link to) that concludes that K2 prevents arterial calcification. (One study you link to states only that it is a *plausible* hypothesis.) And key people involved in the Utrecht studies are marketing K2 in a very big way (Formed a production company.) Why, after some years, haven’t their claimed findings been duplicated? (Or can someone point to a study where they are actually duplicated?)

    Jared Israel wrote on January 24th, 2011
    • Go to this website to find studies:

      For patients on anticoagulation therapy, we recommend them to contact their physician for consultation prior to taking vitamin K2. However, based upon NattoPharma documentation, population studies (see e.g. The Rotterdam study) and traditional uses of natto meals, supplementation in the range below 45 µg represents no safety issue for such patients.

      So fare no cases has found place where k2 (very important “k2” and not “k1”. in any way damages patients taking anticoagulant medicine. Saw an interview were that was stated by a leading researcher..

      Morten wrote on March 30th, 2011
    • Good point…the Utrecht researchers are involved in the marketing of MenaQ7 too and stand to gain, at least in prestige, if the sales take off. It’s what you call a conflicting interest.

      Chris Aylmer wrote on January 28th, 2013
    • Good observation, Jared — but there is a large chunk of information that you are missing called the VKDP, which stands for the vitamin K dependent proteins. They have been researched all over the world. These are enzymes that are activated by vitamin K2; a dozen of them were identified long before the Maastricht (Utrecht?) studies were done.

      One of the VKDP prevents calcium deposits in the arteries, deposits that make plaque more likely to rupture under stress, such as a blood pressure spike. (We all accumulate plaque as we age.) Another VKDP enables calcium and magnesium to be deposited in our bones, building strong bones in kids and preventing osteoporosis in the elderly.

      Nutritionists wanted to believe that vitamin K1 could activate those proteins, (wonder why?) but studies done in the U.S. and elsewhere have shown that it does not do so, even at high dietary intakes. You could take a 5 g K1 supplement to do the job, but a 1 mg K2 supplement will do that job and many others, such as preventing dementia by maintaining the sphingolipid layer that protects all our neurons–oh, yeah, and all the nerves in our spinal cord, and all the motor nerves attached to them.

      All of these studies have been done outside the Netherlands. And this merely scratches the surface of what K2 can do. Aside from cortisol, glutathione and K2 share the title of the most powerful anti-inflammatory natural substances in the world. To hell with resveratrol–I was once stupid enough to buy that stuff!

      You must be wondering why our news outlets have not been trumpeting the amazing benefits of K2 day and night. The truth is that K2 prevents deaths from heart disease better than statin drugs (43% reduction vs. 30% reduction) with none of the severe side effects. This has been known for years, but what would that news have done to statin drugs, the most profitable prescription drug in the world? And which corporations are paying for half the ads on the nightly news–and giving hundred thousand dollar donations to the campaigns of our senators and representatives?

      Big studies like those in the Netherlands are very expensive. Who is going to fund another one? The drug companies, who fund most of the research at American universities? The NIH, where they have to get funding approval from Congress?

      I think you may be getting the picture.

      Camilla Bishop (chemistry grad) wrote on November 3rd, 2014
  21. Vitamin K2 has made my teeth whiter and more solid appearing now. I used too many antibiotics at one point in my life and also had GERD, corrected by eating a apple prior to bed and correcting my posture. K2 and Vitamin D rock for correcting the appearance of my teeth.

    Brian Sterling wrote on May 18th, 2011
  22. Drink plenty of water too.

    Brian Sterling wrote on May 18th, 2011
  23. I’m 50 yrs old. I seen on TV where Dr. Oz has recommended Vitamin K2 for good bone health. I have OsteoPenne and found that after running for 4 years, my bones are worse. I’m now on Vitamin D (5,000 mg per day) and need to do weight bearing exercises. I’m going to start right away taking Vitamin K2. I’m seeing a specailist at the end of the month for my bones. Thanks for the good advice.

    Karen wrote on August 8th, 2011
  24. is vitamin k2 important in absorption of vitamin E?

    justine wrote on August 9th, 2011
  25. Does vitamin K2 have any affect on the eyes? The reason I ask, the pressure has been up in mine since I started taking it.

    Jane Longwith wrote on August 30th, 2011
    • I think K2 may have caused me to develop an atrophic retinal hole. I am myopic and had floaters before, but I only started developing severe floaters and flashes about a week after starting K2. It also gave me high blood pressure and heart palpitations. I was only taking a tiny dose. Too bad, because other than damaging my eyes and maybe my heart, it made me feel great. Scary stuff. I don’t really understand it.

      C S wrote on December 4th, 2013
      • Vitamin D works with the K-2. If you’re having symptoms like that, look into your Vitamin D levels. There’s also a book by Jeff T. Bowles on the miraculous health benefits of high doses of Vitamin D. Look it up on Amazon.

        Daryl wrote on November 8th, 2015
  26. This, I think explains my craving for caviar with all of my pregnancies. Thanks for all of your posts,keep them coming.

    Jodie Jantz wrote on September 5th, 2011
  27. I appreciated all of the information on vitamin K2. My doctor had never heard of it! But I had heard from a friend about the benefits for osteoporosis. I had been taking Evista and had bad leg cramps from taking it! So, now I’m trying the vitamin for my osteopenia. Should I quit taking my daily low dose aspirin?? I am 66 years old and am on no medications. Thank you!

    Ann Lewis wrote on September 6th, 2011
  28. Mark, what is your opinion on fermented dairy, legumes, and grains. Can they still be part of a primal diet?

    Peter wrote on October 6th, 2011

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