Vitamin K2 sources, function and health benefits

Vitamin K is a fat soluble vitamin, best known for its role in blood clotting and bone health.

The main forms of dietary Vitamin K are two: K1 (phylloquinone) and K2 (menaquinone). K1 is synthesized by plants and its bioavailability is not nearly as good in humans as the K2 form (1). K 2 is the form we get from animal products and is the form we are interested in.

Vitamin K2 is found in animals products like meat, eggs, organs, a Japanese dish called natto, and a high amount is also found in high fat dairy products like butter, cream and cheese. These foods contain more K2 if the animals are grass-fed. Vitamin K2 is also produced by bacteria in the gut. Newborn infants have sterile guts, and are sometimes administered Vitamin K during the first few days after birth, before their intestine gets colonized. The plant form, K1, is found in green leafy vegetables along with some types of fruit.

A picture of Vitamin K2

How it works

Vitamin K functions at the cellular level by catalyzing carboxylation of the amino acid glutamate in certain proteins. These carboxylated glutamate amino acids are called Gla residues. What this basically means, is that Vitamin K alters the structure and function of a few specific proteins, after they have been made.

The main function of those proteins who are altered by Vitamin K is binding calcium, and they are therefore intimately involved in calcium metabolism. The regulation of some of these proteins is modified by Vitamin D and the two vitamins may therefore have a synergistic effect in many cases.

The fact that these proteins function mainly by binding calcium has some important implications:

- First, calcium tends to be removed from the bones, causing reduced bone density and fractures. Research shows that Vitamin K supplementation reduces incidence of bone loss and fractures (2).

- Second, calcium tends to be deposited in the arteries, producing arterial calcification and contributing to heart disease, the world’s nr.1 killer. Research shows that Vitamin K inhibits arterial calcification (3).

There’s evidence that Vitamin K can lessen chances of advanced prostate cancer, the most common cancer in men (4). Vitamin K also reduced recurrence of liver cancer in patients after their treatment (5).

Official requirements are viewed as the amount the liver needs to synthesize necessary blood clotting factors, and therefore deficiency is very rare as the intestinal bacteria produce enough. If viewed from the standpoint of preventing arterial calcification, the requirements may be much higher (6).

In the U.S, the Adequate Intake of either K1 or K2 is listed at 120 mcg/day. However, a study found that 1000 mcg/day was necessary to maximize amount of functional osteocalcin (7), which is one of the main proteins altered by Vitamin K and is highly involved in bone metabolism. The K2 form is much better absorbed, so the required amount of it should be lower.

What to do about it

If you eat a lot of animal food and little gluten grains (which interfere with fat soluble vitamin absorption), then you probably don’t need to supplement. Especially if you eat a lot of high-fat dairy, preferably grass-fed. If your diet is more of a conventional western diet, or if you have arterial calcification, then you might want to consider supplementation.

If you are using anticoagulant medication like warfarin then you should talk to your doctor before increasing your intake of vitamin K, because this vitamin has a large effect on these medications. In fact, blocking Vitamin K function in the cells is the primary mechanism in these kinds of drugs. The problem is that they also tend to block the function of other Vitamin K dependent proteins that are not related to blood clotting.

Humans consumed much more K2 than today in pre-agricultural times, because of their high intake of whole foods and grass-fed, wild animals. One of the shortcomings of the strict paleo diet, in my opinion, is its exclusion of high-fat dairy products, but these are the main sources of Vitamin K2 in our diet today. In fact, people eating the most high-fat dairy products had a whopping 69% lower chance of dying from heart disease than those eating the least (8).

For more information on Vitamin K2, visit Dr. Stephan Guyenet’s Whole Health Source. A lot of what I know about Vitamin K and other fat soluble vitamins I learned from his site, and I found some of these researches there as well.



  1. I’m just hearing about the importance of K2 now, and given my age osteoporosis is a real concern. I do eat Paleo and grass-fed beef is part of my diet. But I don’t eat dairy, as you point out. And I’m curious about the dairy issue, because The Myth Of Osteoporosis by Gillian Sanson indicates that the countries with the highest dairy consumption also have the highest incidence of osteoporosis. Yet, if there’s a lot of K2 in dairy, as you say, it should be the opposite…unless there are other factors in the diet (e.g., high consumption of carbohydrates) that would nullify the benefits of dairy. Any insights to share on this? Thanks.

  2. Hello Gerta, I’m not familiar with high dairy consumption increasing risk of osteoporosis. I’ve seen some studies where it has no benefit, but being downright harmful is something I don’t think is true.

    Perhaps there is something in dairy that promotes osteoporosis but is nullified by Vitamin K2. I’m really not sure, but it would be interesting to explore the matter further sometime.

  3. Thanks for your reply. In the book I mentioned (The Myth of Osteoporosis) Gillian Sanson includes a substantial number of references to studies showing a correlation between high dairy intake and osteoporosis or hip fracture. I won’t reproduce all her references here because they’re so extensive, but one was a prospective study of 77,000 women over a 12-year period measuring milk and calcium consumption in relation to incidence of hip and forearm fractures. “It found that those with the highest consumption of dairy products had more fractures than those who drank less milk.” (Feskanich, D. et al., “Milk, dietary calcium, and bone fractures in women: a 12-year prospective study.” Amer. Jour. Pub. Health 1997; 87:992-997.) She also refers to Hegsted, D.M., “Calcium and osteoporosis,” Jour. Nut. 1986;116:2316-2319, from which she takes this finding: “countries with the highest rates of osteoporosis are the biggest consumers of dairy products.” She briefly discusses Vit. K (but she doesn’t call it K2) and recommends broccoli, leafy greens, and legumes.

    It’s a good, thoughtful book and a new edition has just come out, which I haven’t seen yet. I’m assuming she’s updated her references.

    Please don’t think I’m arguing with you here, I’m just putting forward some info that’s influenced my thinking for a long time and trying to reconcile any apparent contradictions. Dairy consumption will continue to be off my list, but the underlying science continues to intrigue me, and this information about the crucial role of Vit. K2 in particular.


  4. Thanks for pointing this out. I honestly haven’t done much research on calcium and bone health but this is something I should look into soon, perhaps even write a blog post about it.

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