Vitamin K2 is a topic that doesn’t get a lot of attention in the mainstream media, but we’ve definitely talked about it before on the show, and I’ve written some articles about it. Most of what I’ve learned about Vitamin K2, I’ve learned from Chris Masterjohn. So I want to give him big props right up front, because a lot of this material that we’re going to talk about comes from articles he’s written and discussions we’ve had about it. I should actually call him Professor Masterjohn now. I just recently saw that he got a position teaching at a university in New York. I can’t remember the name of it, but it looked pretty exciting. And if I think of anybody that I know that we should call The Professor, it’s definitely Masterjohn.
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In this episode, we cover:
3:45 What Chris ate for breakfast
5:22 The history and importance of K2
17:07 How vitamin K2 protects against heart disease
23:54 Where to find your vitamin K2
28:14 Who should take vitamin k2 supplements?
Links We Discuss
- On the Trail of the Elusive X-Factor: A Sixty-Two-Year-Old Mystery Finally Solved by Chris Masterjohn
Steve Wright: Hey, everyone. Welcome to another episode of the Revolution Health Radio show. This show is brought to you by ChrisKresser.com. I’m your host, Steve Wright from SCDlifestyle.com. With me is integrative medical practitioner and New York Times bestseller, healthy skeptic Chris Kresser. Chris, how are you doing this morning?
Chris Kresser: I’m pretty good, Steve. How are you?
Steve Wright: I’m doing well. We’ve got the new backdrop here. We’re trying a new setup to improve the sound quality.
Chris Kresser: Changing it up. When you moved, everything kind of fell apart, huh?
Steve Wright: Yeah. I’m starting from scratch, and so are the people literally about 30 feet to my left who are working on the road outside.
Chris Kresser: Right.
Steve Wright: They’re starting real heavily on the concrete. So we’re hoping that technology in this Yeti mic might do the job.
Chris Kresser: Great. We’ve got a really good question this week. I’m excited to dive in. This is from Susan. Let’s give it a listen.
Susan: Hi, Chris. You recently spoke about saturated fats, lipids, cardiovascular health, and you’ve also written about the Diet-Heart Myth. Those of us who are interested in the connection between what we eat and our cardiovascular health really want to hear about that missing link, that piece of the puzzle that’s not necessarily making the lipid profile and the saturated fat intake as effective as it could be for cardiovascular health, because of vitamin K2. So I wonder if you might be able to talk more about vitamin K2, and perhaps also how the USA dairy often is not giving us the same opportunity for absorption of K2, as if we had grass-fed cows. If you can talk about those kinds of impacts on cardiovascular health, I’d really appreciate it. Thank you so much.
Chris Kresser: That’s a great question. I’m sure a lot of listeners out there are wondering the same thing. It’s a topic that doesn’t get a lot of attention in the mainstream media, but we’ve definitely talked about it before on the show, and I’ve written some articles about it. Most of what I’ve learned about Vitamin K2, I’ve learned from Chris Masterjohn. So I want to give him big props right up front, because a lot of this material that we’re going to talk about comes from articles he’s written and discussions we’ve had about it. I should actually call him Professor Masterjohn now. I just recently saw that he got a position teaching at a university in New York. I can’t remember the name of it, but it looked pretty exciting. And if I think of anybody that I know that we should call The Professor, it’s definitely Masterjohn.
Steve Wright: So are you suggesting that we change his nickname from Master J to The Professor?
Chris Kresser: Master J is pretty good, but I think The Professor is really—if anybody embodies that archetype, it’s Masterjohn.
Steve Wright: Perfect. Hey, Chris, before we get into the meat of today’s question from Susan, did you have any dairy with your breakfast?
What Chris Ate for Breakfast
Chris Kresser: I didn’t have any K2 with my breakfast—oh, actually, I did. I had pastured egg yolks. So I did something a little different today, not typical for me. I had a green smoothie for breakfast, imagine that. It was homemade almond milk, unsweetened almond milk. I put some fresh spinach in there, avocado, half of a banana, two pastured egg yolks from a local farm, and some coconut milk. That was breakfast today. So I did have some K2 in those pastured egg yolks, as we’ll be talking about.
Steve Wright: Awesome.
Chris Kresser: Let’s get into this question. I want to talk about some background information about vitamin K2, what it is, the history behind it, because it’s pretty interesting. Then we’ll get into where you find K2 in the diet and its importance in cardiovascular disease prevention. We’ll also talk about its use in some other conditions. Then I’ll make some recommendations for who should take supplements and who should just get it in their diet. Hopefully, by the end of this, you’ll know from a practical perspective, everything you need to know about vitamin K2 and how much you should be consuming each day.
Steve Wright: And if not, Chris has got a lot of work on his site.
Chris Kresser: That’s right.
Steve Wright: I guess I shouldn’t say Chris. I should say Professor Master J.
The History and Importance of K2
Chris Kresser: The Professor, that’s right. So I said that a lot of what I had learned about vitamin K2 came from The Professor. And a lot of what he learned about K2 came from Weston A. Price, which is another archetypal professor of sorts. He was a dentist—for those of you that aren’t familiar with him—back in the ‘30s. He did a lot of his work around that time. But he was primarily a researcher who looked at the role of nutrition in health and disease. He traveled all around the world studying traditional cultures that had not yet become industrialized. They were still eating their traditional diet. He found that unlike his patients in the US who suffered from all kinds of dental problems, cavities, really narrow faces, problems with structural development of the face and the jaw, when he went and visited these traditional peoples around the world, they had none of these problems. They had really beautiful teeth, no cavities. They had wide dental arches, great facial structure. He became fascinated by the role that nutrition played in this, and studied the common themes of the diets of all these different people that he looked at. Their diets were really different in some cases, but they all shared common themes. That’s basically what he devoted his life to. If you want to learn more about that, you can check out the work of the Weston A. Price Foundation, which is basically dedicated to sharing his ideas, pioneering research, and promoting the benefits of a nutrient-dense diet.
Way back in 1945, Weston Price discovered something that he called a “vitamin-like activator” that played an influential role in the utilization of minerals, protection from tooth decay, the growth and development of the face—like we were talking about—reproduction, protection against cardiovascular disease, and the function of the brain. He called this compound Activator X. He noted that it was present in butterfat, organs, and the fat of animals that were consuming rapidly-growing green grass. So it was pasture-raised animals, but in particular, pasture-raised animals in the spring and the fall. Weston Price found that this Activator X was at the highest level in the fat of these animals during the spring and the fall, when the grass is growing rapidly. He also noted that this Activator X was found in certain seafood like fish eggs. I just want to emphasize again, especially because Susan mentioned it in her question, that it’s really important to realize that vitamin K2—which we now know is this Activator X—is not found in the fat of animals or the milk of animals that are conventionally raised. If you’re drinking just conventional milk, or even organic milk from cows that are not grass-fed, or even grass-fed milk that comes from cows that are eating mostly brown grass, it’s not going to have the K2, the levels of this Activator X, the vitamin K2, that dairy fat or fat in general from animals that are consuming rapidly-growing green grass would have. That’s a really important thing to realize when we talk about how to get K2 into your diet, which we’re going to come back to later.
Steve Wright: Do we know the reason behind that? Does it have something to do with chlorophyll or something like that?
Chris Kresser: Yeah. Well, it’s something to do with vitamin K1. And animals convert K1 into K2, and K1 is much higher in rapidly-growing green plants. That’s where you see the highest concentration of vitamin K1. So Price unfortunately died before research from Russian scientists became known in the West. You know, there was a big divide for a long time. There wasn’t much communication in the scientific community. This research though, when it became known in the West, revealed that the Activator X compound that Price had discovered is actually a form of vitamin K, which we now refer to as vitamin K2. K2, unlike K1, is produced by animal tissues—including the mammary glands—from vitamin K1, as I just mentioned. And there’s a quickly-growing body of evidence that confirms discoveries that Price made almost 100 years ago now, that K2 has all of the functions that I mentioned in the beginning of the show: protecting against tooth decay, helping us to utilize minerals, promoting healthy growth and development in a developing baby in utero and also early in childhood, protection against cardiovascular disease, and also promoting healthy brain function.
We also know now that vitamin K2 works synergistically with other fat-soluble vitamins like vitamin A and vitamin D. Price was a big advocate of making sure that you have a synergistic relationship of all of these vitamins in your diet. That’s something that the Weston A. Price Foundation has done a really great job of elucidating and promoting.
These are really complex relationships between these fat-soluble vitamins. We’re not going to go into excruciating detail because of show length. If you want to go into that kind of detail, you can check out The Professor’s website. You can Google Chris Masterjohn and vitamin K2. He has an article on the Weston A. Price website that goes into more detail than I’m sure most people will care to go into on vitamin K2. If you’re interested, you can check that out. I’m going to just summarize the relationships here. The basic idea is that vitamins A and D signal the cells in our body to produce certain proteins. Vitamin K activates those proteins that are signaled by vitamin A and D. So if you don’t have enough vitamin K, then vitamins A and D can signal those proteins, but they won’t be activated. The cycle won’t be complete. That’s the basic way that they work together.
Now, there’s a debate in the scientific community about whether K2 should be considered essential. Remember, when a nutrient is considered to be essential, it doesn’t just mean it’s really important, which it would be. It means that the body can’t synthesize it on its own, and we actually need to get it from the diet. So that’s the definition of essential in this context. Right now, only vitamin K1 is considered to be essential. Both K1 and K2 are cofactors for the enzyme that activates vitamin K-dependent proteins, but the liver uses vitamin K1 primarily to activate clotting factors. So vitamin K1 helps with blood clotting. Most other tissues preferentially use vitamin K2 to activate other K-dependent proteins. So it’s pretty clear that we need both vitamin K1 and K2 to function optimally. But the conventional line of thinking is that we only need to worry about consuming K1—which is found in rapidly-growing green plants, as I mentioned—because animals, including humans, have the capability of converting K1 into K2. But, and you knew there was a but coming here, there’s several lines of evidence that suggest that this conversion of K1 to K2 is not efficient, and relying on K1 to produce our K2 is not a good idea. One is that studies have shown that the breast milk content of K2 in lactating women who consume K1 supplements does increase, but their blood levels of K2 do not go up. So a woman who is breastfeeding, she takes a K1 supplement, the K2 levels of her breast milk go up, but the K2 levels in her blood do not go up, which suggests that the conversion isn’t necessarily happening in the same way all throughout the body.
Steve Wright: Unless she had adequate levels of K2 prior to the study.
Chris Kresser: Yeah, which a lot of people don’t. The levels of K2 in the US are low. This gets to another problem, which is, right now, there’s not a very reliable test for K2 in the blood. I actually believe that The Professor is working on that, and that’s a contribution that he hopes to make. But that’s one of the problems with this whole area. The other thing is we have a limited ability to absorb K1 from plant foods. In the US, where the average intake is about 150 micrograms per day of K1, blood levels do increase with increasing dietary intake, up to about 200 micrograms per day. But after that, the blood levels just plateau. They don’t continue to go up. In the Netherlands, where the average intake of K1 is a lot higher at 250 micrograms per day, you see no relationship whatsoever between dietary intake of K1 and serum levels of K1. What all this suggests is that humans don’t really have the ability to absorb more than 200 micrograms of vitamin K1, and that humans may need to consume preformed vitamin K2 for optimal effects, rather than relying on the conversion of K1 to K2.
There’s something else that’s important to point out. I’ve talked about this in a lot of other contexts, for example, the conversion of short-chain omega-3 fats like alpha-linolenic acid—that are found in flax and walnuts—to EPA and DHA is very inefficient in many people. The conversion of beta-carotene, which is a vitamin A precursor to retinol-active vitamin A, is also very inefficient in people. And all of these conversions rely on the function of certain enzymes, right? These enzymes, in turn, rely on the presence of certain nutrients, which a lot of Americans are deficient in. They also just rely on the body functioning optimally. So if you have someone who’s nutrient deficient, which a lot of Americans are, and they’re sick, which a lot of Americans are, then their conversion, ability to convert K1 to K2—which even under optimal circumstances, might not be that great—is going to be further impaired. So it’s just another reason not to rely on dietary intake of K1 for your K2 levels.
The last piece of evidence that suggests that eating K2 is a better idea than relying only on K1 is that vitamin K2, in clinical studies, is at least three times more effective than vitamin K1 at activating proteins related to bone metabolism, which is one of the main functions of vitamin K2. That definitely suggests that eating K1 does not have the same effect, at least in terms of bone metabolism, as eating K2. So that’s a good segue into talking more about vitamin K2’s role in protecting against heart disease.
How Vitamin K2 Protects against Heart Disease
One of the main functions of K2 is to regulate calcium metabolism. It basically makes sure that calcium gets into the bones and teeth where it belongs, and stays out of the soft tissue where it doesn’t belong. The reason this is important for heart disease prevention is that calcification of the arteries, which of course are soft tissues, is a huge risk factor for heart disease. In fact, when you look at the scientific literature, the calcium score test, which measures calcification of arteries, is far more predictive of your risk of heart disease in the future than your cholesterol. So this is a big issue.
Cardiovascular calcification can begin as early as the second decade of life, and it’s pretty much ubiquitous by the time people are 65. There are two types. You have calcification of the heart valves in the tunica media, and then calcification of the tunica intima. The tunica media is the middle layer of the artery, and it contains elastic fibers that allow the artery to stretch and accommodate pressure, which is, of course, really important when you have blood flowing through those arteries. Hemodynamics requires that elasticity. Then you have the tunica intima, which is the innermost layer of the artery where atherosclerosis develops. So vitamin K2 keeps calcium out of these tissues and helps them to maintain that elasticity and flexibility, so that the blood can flow freely through those arteries in the heart, and the cardiovascular system can function as they should.
Steve Wright: Is there any theory or thought that once the calcium is deposited into the arteries or into the other soft tissues, that more vitamin K2 might help take it out of there?
Chris Kresser: Yeah, it’s possible. I’ve seen that happen in some of my patients who’ve had a calcium score that was high, and then who’ve taken therapeutic doses of K2, and also done other things, and we’ve seen the calcium score drop. It is possible. Vitamin K2, though, has another role in terms of cardiovascular disease prevention. It appears to protect against inflammation and accumulation of lipids and white blood cells, in that whole process of plaque formation that initiates atherosclerosis. So it’s not just the effect on calcium metabolism. It also seems to be anti-inflammatory and interfere with that whole process of plaque formation. There are probably other benefits that K2 has that we don’t even know yet, because we’ve only been studying it. It’s only really been identified for the past few decades, and there’s a lot more work to be done.
When you look at the actual studies examining the relationship between K2 intake and heart disease, probably the most famous study, the biggest one was the Rotterdam Study, which looked at 4,600 men who are over 55, which, of course, is the high-risk age group for heart disease in the Netherlands. In that study, they separated the intake of K2 into three groups. The group with the highest intake of K2—which I believe was 33 or 35 micrograms per day—was associated with 52% lower risk of severe aortic calcification, 41% lower risk of coronary heart disease, 51% lower risk of death due to heart disease, and a 26% lower risk of death due to any causes. Those are pretty big numbers, pretty significant numbers. What’s really interesting about that is even though the study population consumed 10 times more K1 than K2, there was no relationship between vitamin K1 intake in any of those risk markers that I just mentioned. So once again, that’s pretty strong evidence that eating K1 in plants is not going to give you the same benefit as eating the preformed K2, which is almost exclusively found in animal products, with a few exceptions, which we’ll talk about.
Steve Wright: In the Rotterdam Study, did the participants use supplements or were they using a specific type of food?
Chris Kresser: No, it was food. Probably in the Netherlands, mostly cheese and eggs is what they were getting their K2 from, which are two of the bigger—hard cheeses in particular is one of the highest sources of K2. They tend to eat more pastured eggs in the Netherlands, and pastured eggs are double the amount of K2 than conventional eggs. So that was just from dietary intake. What’s also notable from that study is the really profound effects from even relatively small amounts of dietary K2. We’re talking about 25% decrease in overall risk of death, a 50% decrease in death related to heart disease, from just a few micrograms of a substance, tthe difference in intake was pretty small. The lowest group was under 21 micrograms per day, and the highest I think was over 33 or 35; I can’t remember exactly. The middle must have been somewhere around 27. We’re talking about a difference from the lowest to the highest of like 15 or 20 micrograms, and we’re seeing this effect size. So I think there’s really good news in that. It means you don’t have to necessarily take a supplement with like 10 milligrams of K2 to get the benefits that we’re talking about. We’re talking about the benefits that can be obtained by the difference between eating two extra egg yolks in a day versus not eating any.
Steve Wright: That was going to be my next question. Is there any sort of food quantity you could tell us the micrograms of?
Chris Kresser: Yeah, yeah. A pastured egg yolk is 32 micrograms.
Steve Wright: That’s raw or cooked?
Chris Kresser: I’m not sure. And I don’t know if it makes a difference with K2. I don’t think it does.
Steve Wright: Cool.
Chris Kresser: Given that the intake in the study, as I said, were people with over 37 micrograms a day, if you just ate two pastured egg yolks a day, you would be basically in that higher intake group safely, with no other K2 intake, and you’d be at a much lower risk of heart disease. That’s pretty cool to know. So hopefully, by now, you’re convinced that eating some vitamin K2 is a good idea, particularly if you’re worried about heart disease prevention or your bones, because as I said, K2 regulates calcium metabolism. So it helps prevent osteoporosis and can help actually even treat osteoporosis as well.
Where to Find Your Vitamin K2
Where do you get it? There are several different forms of vitamin K2 actually. It’s more accurate to talk about them as a group of compounds. The main ones that are found in foods are MK-4, and then you’ve got MK-7 through MK-10. MK-4 and MK-7 are the best known. MK-4 is found in animal food—like we said, the fat and the dairy products from pasture-raised animals, typically. MK-7 is produced by bacterial fermentation. So you’ll find it in sauerkraut. Kefir is particularly good, because it’s both animal fat and fermented. Then you find it in our own gut. Our own gut microbes will make some K2 from the K1 that we eat.
Now, there’s still some controversy over whether these forms are equally effective or which is more effective than the other. There aren’t any studies yet that I’m aware of that directly compare the effects of MK-7 with MK-4, but we have several studies that show that they’re both effective. Most of the studies that have been done, like intervention studies, have used the MK-4 form, but there are also studies that have shown that MK-7 is very effective. I don’t think it really matters that much. At this point, I wouldn’t get hung up on that. I would just make sure you’re getting enough. So the highest food source by far of K2 in terms of just quantity of micrograms per serving is natto. Natto is a fermented soy product that is popular in Japan. I think it is one of the nastiest-tasting foods I’ve ever had. Have you tried it, Steve?
Steve Wright: I’m still afraid. I haven’t even tried it.
Chris Kresser: It seems to be one of these foods that people either—maybe there’s some epigenetic thing that turns on or off an affinity to it, because some people actually don’t mind it at all, but some people are just repulsed by it. Unfortunately, I fall into that second category. But it’s a K2 powerhouse. If you like it, you’re really lucky, because it has about 1,100 micrograms per serving. So if we’re aiming for, from a dietary perspective, 50 micrograms per day to put you in that upper intake group, that’s 350 micrograms a week, right? You could basically eat one serving of natto every three weeks, and you’d be meeting your K2 needs. The next one down from that is a long step down. It’s another food that’s not typically consumed here—it’s goose liver. That’s 369 micrograms per serving. If you like goose liver and you can get it, awesome. The next one down from that is another pretty big step down, and that’s hard cheeses. Those are about 76 micrograms per serving. Pasture-raised, of course, is going to be better than conventional. Soft cheeses are 56 micrograms per serving. It’s the same deal—pastured is better. Pastured egg yolk is 32 micrograms per serving. Conventional egg yolks have 15. So it’s not that there’s no K2, but there’s less than half, as you can see. Pastured butter is about 15 micrograms per serving. So if you’re eating butter liberally, it can help a lot. Chicken breast or leg, interestingly enough, has 9 micrograms per serving. Unfortunately, for vegans, especially for those who don’t like natto, the highest plant food other than natto is 4.8 micrograms per serving, and that’s sauerkraut. So you’d have to eat six or seven servings of sauerkraut per day, or maybe other fermented vegetables, to get that same level that you get from eating a couple pastured egg yolks, or maybe even just one pastured egg yolk.
Who Should Take Vitamin K2 Supplements?
My general recommendation, for people who are healthy and just want to stay healthy, who aren’t dealing with osteoporosis or heart disease, would be to eat liberal amounts of hard cheeses, eggs, pastured egg yolks, butter, kefir made with raw milk from pastured cows—especially in the spring, in the fall—is excellent for K2. Of course, a serving of natto per week or even every two weeks would do the trick too, if you’re up for that. And if you are, more power to you.
But, of course, some people may not be eating—if you’re a strict Paleo or if dairy doesn’t work for you and you don’t even consume ghee, and natto isn’t your cup of tea either, then that’s when supplementing might be a good idea. Again, I think it’s fine to take either the MK-7 or MK-4 form. I don’t really see evidence that that matters that much. If you’re just trying to mimic the dietary intake that has shown to be protective in these studies, I think 100 micrograms a day would be sufficient for general maintenance. But if you are trying to prevent a disease that you’re at high risk for, let’s say you have a really strong family history of heart disease and you’ve got several risk factors for heart disease—like high blood pressure and you’re overweight and you have high blood sugar—and you’re just concerned about heart disease prevention, or if you are at risk for osteopenia or osteoporosis, or you already have any of those conditions which indicate poor bone density, or you have cavities and you have a lot of dental problems, a lot of issues with your teeth and the structure of your teeth, then a therapeutic dose of K2 can be much higher. In the Japanese osteoporosis studies, where they use K2 therapeutically for people with bone problems, they use huge doses of K2, as high as 45 milligrams a day. Up until now, we’ve been talking about micrograms, right? 1,000 micrograms is 1 milligram, and the Japanese studies use 45 milligrams. So we’re talking about orders of magnitude higher doses.
Steve Wright: So 45,000 micrograms, right?
Chris Kresser: Yeah, exactly. We’re talking about really, really large doses. But they were very effective, and there were no adverse effects noted in the studies. Vitamin K2 seems to be very safe even at these higher doses. So I have used really high doses. I’ve never used more than 30 milligrams with osteoporosis patients. With patients who are concerned with heart disease prevention, I think something like 5 milligrams would probably be sufficient. I don’t know of any reason to go higher than that. In terms of what brand or particular product I recommend, it can obviously be a bit difficult to get even 5 milligrams, much less 30 or 45 milligrams, if you’re taking—you know, most of the capsules and tablets have 50 micrograms or 100 micrograms. You’re going to be swallowing a lot of pills. Thorne Research makes a product with vitamin K2 drops: one that has vitamin D in it, and one that doesn’t. I sell them in my store at Store.ChrisKresser.com, because this is by far the easiest way to dose it. I think one drop is equal to 1 milligram. So if you want 5 milligrams, you just do 5 drops, and you’re done. It’s a really easy way to do it.
Steve Wright: Hey, Chris, when it comes to therapeutic doses like this, we talked earlier in the show about the synergistic sort of cofactor-ness of vitamin A and D. What sort of cofactors should people be looking at stacking with this?
Chris Kresser: Perfect question. That was the last point I wanted to make. When you’re taking a high dose of any of the fat-soluble vitamins, you want to make sure you’re getting enough of the others. I would recommend if you’re taking a high dose of K2, that you also take cod liver oil, which is high in vitamin A and vitamin D. There is a form of K2 that Thorne sells that has some vitamin D in it. That’s why they put it in there—they understand that there’s some synergism there. So either making sure you’re eating enough liver, which has vitamin A, and making sure you’re getting enough vitamin D in cold-water, fatty fish, or in cod liver oil or supplementing, is a really good idea while you’re taking that kind of K2. So that’s the lowdown on K2. I hope that was helpful. Let us know what you think in the comments section. We’ll see you next week.
Steve Wright: Thanks for listening, everyone. If you want more information between next week’s podcast, obviously beyond Chris Kresser’s email list—if you haven’t joined that, you should definitely do that. If you’re on social media, whether Twitter’s your game or Facebook’s your ideal place to connect, Chris is on both places at Facebook.com/ChrisKresserLAc and Twitter.com/ChrisKresser. Go follow him over there, and you’ll get a bunch more info. Thanks for listening.
Chris Kresser: Thanks, everyone.