ACSH Explains: What Are Vitamins?

By Ruth Kava — Nov 01, 2017
The term "vitamin" is so common that you'd expect most people to know what it is. However, if that were true we wouldn't have phony vitamins like "B17" being sold on the Internet. The lesson is that you can't just call something a vitamin – and have it be one. Here's how you can tell the two kinds apart.

Sure, everyone ‘knows’ what vitamins are — they’re those substances in the pills you take with OJ every morning, and if you don’t, you’ll get sick. And at least some of that is true (although the supplement industry would like you to believe the part about the pills).

One thing we know for sure about vitamins is that they are organic chemicals (see my colleague Dr. Josh Bloom’s explanation of ‘organic’ here) that are essential for life. That means that if you don’t consume a vitamin for long enough and your body is depleted of it, you will eventually get quite sick and die. On the way, you’ll get a disease from the deficiency, such as scurvy from lack of vitamin C or pellagra from a niacin deficiency.

But that’s just one of the few things vitamins have in common with each other. Although you might think they’d be similar in chemical structure, that’s not even close to being true, as you can see from the examples of thiamin, vitamin C and B12 below.

Cobalamin (Vitamin B12)

Thiamin (Vitamin B1)


The name ‘vitamins’ arose because the first one discovered, thiamine (also known as vitamin B1), has an amino group in its structure. Thus the term vitamin is actually a contraction of ‘vital amine’. There are currently 13 compounds recognized as vitamins, both with and without amines, as shown in the table below. Both common and some of their chemical names are given:


Common Names

Chemical Names

Vitamin A


Retinol, retinal, and some carotenoids including beta carotene


Vitamin B1



Vitamin B2



Vitamin B 3


Niacin, niacinamide, Nicotinamide riboside


Vitamin B 5


Pantothenic Acid

Vitamin B6


Pyridoxine, pyridoxamine, pyridoxal


Vitamin B7



Vitamin B9



Vitamin B12

Cyanocobalamin, hydroxocobalamin, methylcobalamin, adenosylcobalamin


Vitamin C

Ascorbic Acid

Vitamin D

Cholecalciferol, Ergocalciferol

Vitamin E

Tocopherols, tocotrienols

Vitamin K

Phylloquinone, menaquinones


Although other drugs have been called ‘vitamins’ in popular literature or on the Internet, they are not. These fake vitamins have not passed the tests of being essential or having a unique and essential function. When non-vitamins are given the term, it is simply done to sell products such as so-called vitamin 17 or laetrile, which is actually derived from cyanide-containing apricot pits.



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