Labrada's 100% Whey Protein is an excellent source of all the essential amino acids and is extremely rich in the Branched Chain Amino Acids (BCAAs), leucine, isoleucine, and valine. BCAAs make up one-third of muscle protein and are important to athletes because training increases the body's demand for them. An adequate supply of BCAAs in the blood is insurance against loss of muscle size and strength.