What are vitamins?

My six-year-old asked me this recently and I couldn’t give him an answer that satisfied me. What are vitamins? Is it just a catch-all term for “things the body needs that aren’t minerals”? Also, there’s B1, B6 and B12. Why is the B-group divided up like that, while there’s just one vitamin A, one vitamin C, and so on? Do vitamins B2, B3, and so on exist?

Sorry to ask so many questions at once, but those of you who know 6-year-olds know where I’m coming from :eek: Looked through the archives and didn’t find anything that helped…


A vitamin is an organic (carbon-containing) compound necessary for health in only tiny amounts. Minerals are excluded because they are not organic. Sugars, etc., are excluded because they are needed in more than minute amounts. The first vitamins discovered were chemically amines, hence the word vitamin (“life amine”). Many vitamins are not actually amines.

There are more than just one form of vitamin A: retinol is made in the body from alpha-, beta- or gamma-carotene, A[sub]1[/sub] and A[sub]2[/sub] are found in fish liver oil. There are likewise at least four different kinds of vitamin D; several different types of vitamin E (tocopherols, of which the best known and most potent is alpha tocopherol); at least three kinds of vitamin K, etc.

All the B vitamins are coenzymes, meaning they are closely associated with enzymes. Many important enzymes can’t work or can’t work well without one of the B vitamins. I’m sure there are substances that have gone by the names vitamin B[sub]n[/sub] where n is any integer between one and twelve. I’m not sure what all of them are. B[sub]2[/sub] is an old name for riboflavin. B[sub]1[/sub] is an old name for thiamin. B[sub]3[/sub] is also called niacin (there are at least two forms of this, niacinamide and nicotinic acid). Some of them may have turned out not to be vitamins at all. Some of them may have turned out to be necessary for some animals but not for humans. Some of the B vitamins never got a number designation. (e.g., folic acid is a B vitamin, but is usually just called “folic acid” or “folate” but sometimes called vitamin M).

I stand corrected. I see in the page Stupendous man linked to that folic acid is also called vitamin B[sub]9[/sub]. I am hoping KarlGauss will be along to illuminate things further. I’m intensely curious to learn what the heck 4-5, 7-8, and 10-11 are.

I found some more information, probably more than you ever wanted to know. Not all of the below are necessarily true vitamins (I wouldn’t know). In many cases there are other chemicals that can be substituted (niacinamide and nicotinamide both have vitamin B3 activity, for example). It can be very confusing because many of the numbers (4, 7, and 8 I think) originally referred to bird nutrients that turned out not be necessary for human health. Later choline, biotin, and inositol were assigned those numbers but some (but I don’t think those assignments are official).

B1 - thiamin
B2 - riboflavin
B3 - nicotinamide
B4 - adenine and/or choline ?
B5 - pantothenic acid
B6 - pyridoxine
B7 - ? / biotin
B8 - ? / inositol
B9 - folic acid
B10 - necessary in at least some birds
B11 - necessary in at least some birds
B12 - cyanocobalbalamin
B13 - orotic acid
B14 - ?
B15 - pangamic acid