u might want to check this article out, im going to write more about b12 very soon, its a big topic with a lot of grey areas, i dont have all the answers but im big on researching about it, also be sure to check the comments very interesting...
https://steemit.com/vegan/@celestialcow/uncovering-the-vitamin-b12-myths-part-1-mushrooms-the-flesh-of-the-gods