B-12 is a by-product of certain strains of bacteria. The friendly bacteria float in the air, are blown by the wind, and collect on grasses, leaves, fruit and so forth. However, with today's food handling methods, it is rare to have B-12 on plants-based foods by the time they arrive in the grocery store. Animals consume it in their food chain and therefore are good sources of B-12. Our plant-based food sources today are deficient in B12. If you do not eat animal-based foods of any kind, then It wise to supplement both vitamin B-12 and vitamin D. B-12 and vitamin D are often found to be deficient among pure vegans, which can and does lead to some fairly serious problems. For this reason, I continue to use some fresh eggs and dairy in my family's diet. I prefer this to supplements, although I have recently formulated a whole plant-based supplement that has adequate B-12. I don't know that I will produce the supplement, even for personal use. As per animal-based foods, we are selective about the milk and eggs we buy. They are farm fresh from local free-ranging animals. Even at that, our use of these foods is minimal, which is all that is required to consume adequate B-12.