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Question: I would like to know about different sources of vitamin K2. I have been told it is from natto or fermented soy and from a flower called geraniol. Can you tell me the difference? Is one source better than another?
Answer: Two forms of vitamin K2 are typically found in supplements: MK-4 (synthetic) and MK-7 (natural, from natto). There are significant differences between them: in paticular, MK-7 has a longer half-life, so a smaller dose can be used. Two newer forms of MK-7 are available that are synthetic. Get the details in the Review of Vitamin K Supplements, which includes our tests and comparisons of products containing both forms of K2 as well as vitamin K1.