L-Isoleucine is one of the three essential amino acids (L-Leucine, L-Isoleucine and L-Valine). All three are considered essential amino acids; they cannot be made in the body and must be consumed in the diet from protein-rich foods. BCAAs account for 35% of the essential amino acids found in muscle proteins. BCAAs are unique in that they can be oxidized in skeletal muscle, whereas other essential amino acid are mainly catabolized, or broken down, in the liver.
L-Isoleucine and musle building
BCAAs and especially leucine are key stimulators of protein synthesis or muscle building and also play a role in the prevention of muscle breakdown. BCAAs are unique from other amino acids in that they can be oxidized in the muscle for fuel. As a result, it is thought that BCAAs can be used as fuel during exercise, producing performance benefits especially in longer-duration endurance sports. Because of the role BCAAs have in the regulation of protein synthesis and protein breakdown, it is believed that they can be used to prevent the catabolic effects of exercise when supplemented before or during training and used to enhance muscle building or protein synthesis when supplemented postexercise. In addition, many believe that BCAAs can have performance-enhancing effects due to their ability to be oxidized and used for fuel by the muscles. This belief has prompted many endurance athletes to supplement with BCAA before and during competition or training.