What’s in a name..? The case of the missing B vitamins.
There are currently eight confirmed B vitamins required by Humans. The eight are vitamins B1, B2, B3, B5, B6, B7, B9 and B12. So… what happened to B4, B8, B10 and B11?!
Well, it boils down to a combination of history and how we define a vitamin. Vitamins, of course, are vital (the ‘Vit’ in‘Vitamin) components of human health that cannot be made by humans, and thus need to be obtained through dietary consumption. As we began a parade of vitamin discoveries over the past 100 years or so, we ‘discovered’ new B vitamins as we went along. We named these new B vitamins often in the order we found them. B12 is the last confirmed B vitamin we have discovered to date, for example. The problem then arose was the simple fact that as we explored the human biochemistry of these vitamins, we discovered something we didn’t know when we first named them….. Humans could make some of them! Turned out they were not all tied to diet at all, and thus some could not, by definition, be called vitamins anymore. So, B4 (adenine), for example, placed between B3 (niacin) and B5 (pantothenic acid), is now ‘simply’ adenine; It is still a critical component of energy regulation and found in our DNA and RNA, but is not a ‘vitamin’ anymore. We have not, however, ever gone back and reshuffled the names down a few numbers - such would make it way too confusing to follow along if we suddenly had a new B4, which used to be the old B5! Hence we have missing “B vitamins.”