Casein is the protein most abundant in milk. As a result of the way it forms during the processing of milk, casein tends to be a gelatinous material. Once formed into protein powder, it becomes a slower acting form of protein that is absorbed by the body at a different rate compared to whey protein.
Casein results in a longer period of heightened blood amino acids – including the branch chained amino acids Leucine, Isoleucine and Valine, which help prevent protein breakdown. Where whey protein quickly increases blood amino acids, and therefore quickly aids protein synthesis, casein does so slowly and for longer.