There are a lot of myths about B-12. The most persistent one is that it comes from meat. It&#x27;s actually made by bacteria. Vegetarians and vegans only lack it in modern society because of (a) antibiotic use, harming bacterial population, and (b) &quot;clean&quot; foods, which fails to reintroduce those bacteria, and which lack b12 themselves.<p>Not so surprisingly, the same is true for modern animals including farmed cows and pigs. I can&#x27;t find a the source now (and apparently neither can wikipedia editors, cause they deleted it), but a very significant percentage of B12 production today (some say upwards of 80%) goes to animals. Some of it for their well-being, but most of it for the people eating them. A contender for the &quot;least-efficient-way-to-supplement-vitamins&quot;, I think.<p>Also, many non-vegans and non-vegetarians suffer from B12 deficiency these days.