The branched chain amino acids (BCAAs) L-valine, L-leucine, and L-isoleucine enhance protein synthesis in liver cells and muscle cells. Because they can be oxidized in the cell’s mitochondria, the branched chain amino acids may also provide energy and may serve as fuel sources for skeletal muscles during periods of metabolic stress. As a result, BCAAs have been used with success to support liver function. A recent study also showed BCAAs supplementation improved insulin resistance and beta cell function as well as energy metabolism and glucose tolerance in certain people. They are also used by athletes to improve mental and physical performance and repair the microtears that are a normal result of exercise. Branched chain amino acids also reduce perceived exertion and mental fatigue during exercise.