Thanks for expanding on my points! Yep as I said, fermented foods and your gut are sources of k2. Vitamin K is the generic term for all compounds that have the same role in blood clotting, so that's why I was referring to them all under vitamin K or as well collectively compounds considered k2 etc! The vitamins roles in bone health are actually way less established than we think. Basically it is used to carboxylate glutamic acid, making it have a charge of 2- in its ionized form. Because of this, it can then bind to calcium ions. This contributes to calcificstion of bones, and also helps prevent calcification of soft tissues, but the definite role/mechanism isnt as clear. What we do know is its primary role in blood clotting. Vitamin K is used for conversion of fibrin to fibrinogen, which is why deficiency symptoms are basically just hemorrhage etc. Since vitamin K is regenerated after use through the vitamin K cycle, and since it's in so many foods, and we can absorb it from our guts, supplementation is really unnecessary, that's what I'm saying :p good to know that k2 supplements exist though.