Optimum Nutrition Gold Standard 100% Whey is made of whey isolate, which is one of the purest types of protein and is the first source of protein for building muscle. It contains essential amino acids that are not manufactured by the body, including the three BCAAs (leucine, isoleucine and valine).
Features of Optimum Nutrition Gold Standard 100% Whey

Primary source of protein
Pure Muscle Building Protein
Enriched with Ultra Pure Whey Protein Isolate
Rich in BCAAs
Rich in glutamine.
Contains aminogen-digestive enzymes to enhance breakdown and absorption
Easy to dissolve in water or other beverages
Added to lactase enzyme to digest milk sugar