VITAMIN K2 – why I take (but don’t necessarily recommend) it!

VITAMIN K2 – why I take (but don’t necessarily recommend) it!

Vitamin K is a group of structurally similar
vitamins required for carboxylation of certain proteins in the human body, thereby activating
them. The classic example is activation of proteins
in the blood clotting cascade in the liver – vitamin K is used to add a carboxyl group
to some of the clotting proteins, hence converting them to their active form and allowing them
to do their job. But there are many other relatively recently-discovered
proteins outside the liver that also require this modification to become active. There have been at least 10 more of these
gla proteins discovered, involved in everything from bone mineralisation to embryonic development. Many of these proteins are active outside
of the liver. The reason I bring up location relative to
the liver is that this is what makes the fundamental difference between the different forms of
vitamin K important – ability to make it past the liver and into the general circulation. Without getting into too much detail, the
crux of the matter is that vitamin K1, or phylloquinone, is relatively hydrophilic,
whilst K2, or menaquinone, tends to have a more hydrophobic tail, essentially allowing
it to be transported and remain in the blood longer, which in turn allows it to get to
tissues outside of the liver. But to complicate matters even more, vitamin
K2 is again subdivided according to how long this tail is, and the length of this tail
further impacts it’s ability to make it around the body. The chain length is designated by the number
following ‘MK’ in vitamin K nomenclature. For example, MK-4 is short making it relatively
more hydrophilic like phylloquinone, whilst MK-7 is longer making it more hydrophobic. The most important forms for human health
are MK-4 and MK-7. MK-4 is the form most commonly used in animal
tissues, thus animals, including humans, have the ability to convert K1 into MK-4. The concern is that this conversion is under-explored
in humans, and may not fully meet demands, especially considering that there may not
be much K1 circulating in the first place as we have discussed. This is why it intuitively makes sense to
take in the MK-4 form. However, when this is studied, it appears
that not much MK-4 makes it into the circulation following acute or consecutive supplementation
partly due to it’s relatively hydrophilic nature and possibly absorption issues, although
a relatively low dose was used in this experiment. And it follows that we need large doses of
MK-4 to carboxylate extra-hepatic gla proteins, which remember is the reason why we are interested
in taking K2 it in the first place. Enter MK-7. MK-7 has a much longer half-life in the blood
and appears to be better at carboxylating these proteins. Not only does it seem to be cleaved into MK-4
in the tissues, but MK-7 may actually be the specific form needed in some tissues. Conversely, MK-4 cannot be converted by humans
to MK-7. So it seems we get the best of both worlds
from MK-7, and that is why it is the preferred form for supplementation and the best-studied
form. But let’s leave the discussion on supplements
aside for now. What are the dietary sources of vitamin K? The most well-known source is dark green leafy
vegetables and other plant foods, but what you may not know is that they only provide
K1. As we have seen, animals, including humans
convert K1 to MK-4, so this is the predominant form found in non-fermented animal products. But the only organisms capable of producing
the long-chain menaquinones, MK-7 and upwards, are fermenting bacteria. That is why this is the predominant form found
in fermented foods and produced in the large intestine. But as we will see, the bioavailability of
these long-chain menaquinones produced by gut bacteria is uncertain. So given that dark green leafies provide only
phylloquinone, animal products provide primarily MK-4 and we don’t know if we absorb much of
the MK-7 produced in our gut, does that mean we have to rely on fermented foods, of which
really only nattō is a good source? I am going to preface the following discussion
answering that question by saying that this whole area is not at all well-studied – in
a situation analogous to choline which I discussed in my last video, different forms of vitamin
K are simply not a research priority or a big public health concern, so we cannot answer
these questions comprehensively due to the lack of data. As I mentioned earlier, animals, including
humans, can convert phylloquinone to the MK-4 form of menaquinone in some tissues, but this
conversion appears to be variable and perhaps incomplete. However, we must bear in mind that these proteins
are still getting carboxylated to some degree and performing their functions somehow, despite
the fact that though almost no-one eats nattō on a regular basis or supplements K2. Likewise, taking anicoagulant drugs that interfere
with vitamin K activity increase the risk of calcification and fracture, so we know
that the vitamin K most of us are getting is doing it’s job. This is one of the reasons why nutrition authorities,
most recently the European Food Safety Authority in 2017, do not set specific dietary reference
intakes for the different forms of vitamin K. The evidence simply isn’t there to tell us
that there is a need to get both forms in for adequate carboxylation and health. It’s also why Cronometer does not have a seperate
bar for K2. That being said, K2 specifically does appear
to possibly have a protective effect. One prospective cohort study found quite an
impressive significantly reduced risk of incident heart disease and heart disease mortality
when comparing the highest tertile of K2 intake with the lowest, whilst a similar study found
no such effect. This is supported by cross-sectional data
suggesting an association between higher K2 intake and less coronary calcification. Similarly, K2 may have a role to play in supporting
bone health, but again the findings are mixed. Additionally, there are other emerging potential
benefits that we are only just beginning to explore. This is no surprise, given the variety of
gla proteins in different tissues. Given that there are potential benefits, the
next area that must be explored is risks and safety profile to help us come to a decision
on whether or not to supplement. K2 MK-7 is widely-regarded to be safe when
taken at recommended doses as a dietary supplement. Because of it’s good safety profile and potential
benefit, and following exactly the rationale I have outlined in this video, I take vitamin
K2 myself. However, because this potential benefit is
small, especially compared with some of the non-negotiable supplements I recommend like
vitamins B12 and D, in addition to the fact that the guidelines do not give recommendations
for K2 specifically based on the best-available evidence, I do not recommend the supplement
to everyone. If, after following my rationale outlined
in this video and of course based on your own research, and if the supplement is within
your means, then feel assured that at worst the supplement is not going to do any harm,
and at best it might actually give you some benefit if you do decide to take it. Notice as well that I said “supplement”, not
source from food, with one exception. There is only one good food source of MK-7
and that is nattō, but by all accounts this fermented soybean food is not very acceptable
to Western palates. Other sources of K2 invariably contain relatively
little K2 and little to no MK-7 specifically. And even if they did, remember the whole point
of why we want to take K2 is mainly to reduce our cardiovascular risk. Non-nattō sources of K2 are almost all fatty
animal products which are now undeniably connected with cardiovascular disease. Indeed, MK-7 supplements are usually derived
from nattō bacteria. So how about dose? Because of everything we have discussed so
far in this video in addition to the fact that there is no good test for vitamin K status,
it is difficult to determine appropriate dosage, but the general consensus is that most of
the benefit can be obtained from the first 100 mcg of MK-7. As with any supplement, make sure you discuss
starting K2 with your doctor if you do decide you want take it because it can interfere
with vitamin K antagonist drugs and theoretically could play a role in destabilising pre-existing
atherosclerotic plaques. If you want my personal opinion, I think there
are undiscovered mechanisms by which we can get the appropriate form of vitamin K to the
relevant proteins. My best guess is that the currently unknown
rate of absorption of MK-7 from the bacteria that produce it in our large intestine is
sufficient to meet our needs in the presence of a healthy intestinal microbiome and a good
intake of K1 for conversion and to spare requirement for K2. I also wonder that because not everyone fulfills
these criteria, if some of the recent conflicting stuff we have seen on vitamin D is down to
this insufficiency of vitamin K along with high doses of vitamin D, but there is no way
of knowing if there is a connection here at present. Either way, there are a number of randomised
controlled trials currently underway pitting MK-7 against coronary artery calcification
amongst other things, with results from this one due in October of this year, so hopefully
they will bring us one step closer to knowing if vitamin K2 supplements are worth taking! In summary, vitamin K2 isn’t one of those
make-or-break supplements like B12. However, there may be some potential benefit
and this area is currently the subject of investigation. For now, the best you can do is to make up
your own mind based on your own research and see if it’s worth it for yourself, whilst
resting assured that the supplement is safe. That’s it guys, hope you learned a little
something about vitamin K2! Give us an old thumbs up there if you found
the video informative and share it with anyone you think might be interested. I’ll be back to ye soon with another nutrient
of concern, so make sure you subscribe if you haven’t already so you don’t miss that
one! Talk to ye soon. Sláinte!

18 thoughts on “VITAMIN K2 – why I take (but don’t necessarily recommend) it!

  1. Do you take vitamin K2?


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  2. Wooow. Awesome compiled video!
    Is anyone ready to produce & distribute NATTO yet…? I'd be the first in line… 😉

  3. natto!!! such an amazing food! didn't know it contains it. I eat it often when i'm in France. I found one made in France and organic! 🙂
    Would be interesting to study Japanese people since they natto almost every morning.

  4. If mk7 supplementation does work in reducing calcification I wonder how the pharmaceutical industry will overcome this, I mean you can't mark up mk7 by thousands of %s, it's easy to produce. I wonder if it will even be implemented into practice if it does work, can you think up of other randomized trials that were ignored ;)? sure they were not double blind but that's not really a good argument against them.

  5. Patient: I'm taking K2.

    GP: Make sure you take an oxygen mask.
    Patient: No, I mean the vitamin, not the mountain.
    GP: What's a "vitamin"?

  6. I have factor five Leiden a blood clotting disorder (causes too much clotting). It is recommended that vitamin k is kept at a minimum. Pretty ironic in a world where eating plant based and dark leafy greens tend to be ideal for everyone else. Nobody is talking about this rare situation that I’ve found myself in. Thought about going vegan but not sure how to navigate this complicated situation. Any recommendations?

  7. so you are basically taking out all the bad foods in your diet and then filling all the deficiencies in with supplements.. which cause cancer anyway.. what a weird waay to do things

  8. @ Des Harrington, I have been taking K2 MK7 100 mcg and vitamin D3 5000 IU, can you recommend how much K2 MK7 or which K2 do you take? Thank you

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