K2 vs K

My K level is usually massively higher than the necessary limit. That's because of eating lots of plants. But is K2 a part of the K numbers? If I have 1000% or more of the K daily recommended amount, am I likely to also have enough K2? I've been reading about K2 so I'm interested in knowing if I have enough.


  • This is a great topic and one that doesn't have a clear answer... yet. Vitamin K1 is found in green leafy foods, where K2 is made in our intestinal tract and the tracts of other species. It is still unclear how much vitamin K2 we absorb, so it makes it difficult to qualify whether or not we are a society with vitamin K2 deficiency. Also, a tiny amount of vitamin K is recycled multiple times in the body, which makes it even more challenging

    There is some research that suggests supplementing with vitamin K2 helps prevent bone fractures, although the results are not overly convincing.

    As a result, my overall advice would be to meet daily intake for vitamin K and don't worry about supplementation unless you have had a fracture or have been diagnosed with osteopenia.

    This would also make for a great blog post!

    Susan Macfarlane, MScA, RD
    Registered Dietitian Nutritionist
    As always, any and all postings here are covered by our T&Cs:

  • Hi Susan,
    Your answers always super clear. I found a lot of vague info online but now I see why. Also, there seems like a lot of fuss about it lately so I was worried, but understanding that no one fully understands or has done enough research yet makes me feel better.

    It's created in our bodies (and other animals).

    Do they know how it's created?

    Do they know if it's dependent on any other nutrients in order to be created? (Like how I discussed with you before how Selenium is needed for the thyroid to produce it's hormones).

    Do they know if regular K helps it get created or is that plain K totally unrelated? Or not known?

    Apart from these question which I'm curious about I feel more relaxed about it for the time being. Thank you for your help. It's really appreciated.

  • @butterfly

    The best introduction to K2 is the book Vitamin K2 and the Calcium Paradox by Kate Rheaume-Bleue. The book's not perfect but it addresses all your questions.

    The most studied variants of K2 are MK-4 and MK-7. They are found in different kinds of foods. You might try to intentionally eat pastured eggs, butter, cheese, or liver. Or, you can give natto (fermented soybeans) a go. Note that these are completely different from the published sources of "Vitamin K" which, usually, ignore K2.

    If one does supplement with K2, it is best not to take it alone, but, rather with Vitamin A (not beta-carotene) and Vitamin D, since all three interact with each other. If you don't want to buy the book you can find a lot of info online by Chris Masterjohn, a professor in New York. But the book I mentioned synthesizes a lot of information, even though it tends to go overboard singing K2's praises.

    Right now, there is still a lot of uncertainty about the K2 content of various foods and none of the Cronometer databases give information on it. (Masterjohn tends to post updated lists of high-K2 foods.) The Vitamin K content shown in Cronometer is K1 or phylloquinone. It is extremely rare for people to be deficient in it. K1 has long been known to be associated with blood clotting ("koagulation" in German and Scandinavian). Given that I once had a blood clot, I would be very careful about have too much K1 in my diet. (When I was admitted to the hospital I must have been asked a thousand times if I ate a lot of broccoli, kale, cabbage, spinach, etc.)

    K2 is known to play a role in trafficking calcium into and out of tissues. Hence it may be important in the treatment of atherosclerosis, osteoporosis, and periodontal disease.

    Most doctors and, unfortunately, many nutritionists have not studied K2, so this, like most things, is a case where you really need to be your own science advisor. Also, as with most things, I would be careful about supplementing. Invariably, supplements are oversold. But, in my opinion, it seems reasonable to seek out to eat more foods with higher K2 content.

  • Hi @butterfly

    Vitamin K2 is produced by various bacteria that live in our colon. However, absorption of vitamin K takes place higher up in the smaller intestine, which is why there is still confusion about how much humans absorb from colonic production.

    While I don’t know of any nutrients that would interfere with colonic production of vitamin K2, I don’t think it’s unreasonable to believe that certain medical conditions that result in altered gut bacteria could influence production. But again, this is just speculation.

    Large doses of vitamin A and E can interfere with vitamin K absorption and if you are taking warfarin, it’s key to not alter your intake of leafy greens as it can interfere with clotting. You also need to be eating enough fat in your diet to ensure adequate absorption of fat-soluble nutrients, like vitamin K.

    As @moies mentioned, there is still a lot of uncertainty about vitamin K2 (as with so many areas of nutrition). I agree that it’s better to choose food over supplements, especially since we don’t know K2’s health effects yet.

    Kind regards,

    Susan Macfarlane, MScA, RD
    Registered Dietitian Nutritionist
    As always, any and all postings here are covered by our T&Cs:

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