Not all proteins are created equal. The source of a particular protein can make a large difference to its effectiveness and efficiency.
Protein Digestibility Corrected Amino Acid Score (PDCAAS)
The official method for measuring the quality of proteins in the Protein Digestibility Corrected Amino Acid Score (PDCAAS). This measures the amino acid profile of the protein against that require by humans and gives a score from 0 to 1. Whey protein isolate scores a perfect 1, meaning it provides all the amino acids required by the body. This score makes it the best protein around.
The quality of a protein as determined by the PDCAAS is only part of the story. A protein may have all of the amino acids required but this is immaterial if the protein cannot be absorbed easily. Biological Value is a percentage score showing how much of the protein is absorbed by the body. Whey protein, along with whole egg, has a perfect score of 100.
Speed of Absorption
As well as the complete absorption level, it is important that the protein can be absorbed as fast as possible to aid recovery after training. Whey protein is digested exceptionally quickly which makes it ideal as a post-workout liquid meal.
If you are on a low calorie diet, a protein’s level of fat will certainly be a consideration. The bigger of an issue this is for you, the more important the purity of the protein. Again, whey protein isolate ranks above any other protein in this area.
On a more practical level, different proteins have a different taste. This is obviously a matter of personal preference, but many people quite enjoy the mild, milky taste of whey protein isolate.