Vitamin
An organic compound required in small amounts that an organism cannot synthesise for itself.
Unit
mg
In depth
Vitamins are classified as fat-soluble or water-soluble. Fat-soluble vitamins are stored in the body and can accumulate to toxic levels, while water-soluble ones are excreted and must be supplied regularly. Most act as precursors of coenzymes.
Examples in the real world
Vitamin C preventing scurvy; vitamin D regulating calcium; the B vitamins forming NAD, FAD and coenzyme A.