BCAAs & EAAs are specific types of amino acids. EAAs are essential amino acids and refer to the group of eight amino acids that cannot be synthesized by the body but must be supplied through the diet. The eight EAA are isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan and valine. Three of them—leucine, isoleucine, and valine—also belong to the BCAA category, which refers to branched-chain amino acids. EAAs are of particular interest as dietary supplements for those who do not get enough amino acids through their regular diet. BCAA supplements are great for those who focus on serious strength training. The three BCAAs make up about a third of skeletal muscle and have been shown to be important for building muscle and effective in slowing down muscle breakdown. BCAAs are metabolized by muscle tissue, which makes the amino acids readily available for building muscle or as building blocks for muscle.