What is whey protein?

Whey protein is a collection of proteins found in whey, a byproduct of cheesemaking. When a coagulant (usually rennet) is added to milk, the curds (casein) and whey separate; whey protein is the water-soluble part of milk. Whey protein is often consumed as a supplement in the form of dry powders with various levels of processing that affect how concentrated a source of protein they are and how fast they’re absorbed. There are three main types of whey protein: whey concentrate, whey isolate, and whey hydrolysate.