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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About the Author

Mark Sisson is the founder of Mark’s Daily Apple, godfather to the Primal food and lifestyle movement, and the New York Times bestselling author of The Keto Reset Diet. His latest book is Keto for Life, where he discusses how he combines the keto diet with a Primal lifestyle for optimal health and longevity. Mark is the author of numerous other books as well, including The Primal Blueprint, which was credited with turbocharging the growth of the primal/paleo movement back in 2009. After spending more than three decades educating folks on why food is the key component to achieving and maintaining optimal wellness, Mark launched Primal Kitchen, a real-food company that creates flavorful and delicious kitchen staples crafted with premium ingredients like avocado oil. With over 70 condiments, sauces, oils, and dressings in their lineup, Primal Kitchen makes it easy to prep mouthwatering meals that fit into your lifestyle.

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