Ciro Santilli The most important on in metabolism internals, everything else gets converted to it before being processed in the .
Nutrient that a given species cannot produce and must ingest in its diet.
en.wikipedia.org/w/index.php?title=Nutrient&oldid=1075972831#Essential gives somewhat of an overview:
Vitamins are essential nutrients that are small organic compounds.
Mentioned at 100 Greatest Discoveries by the Discovery Channel (2004-2005) medicine episode.