Since the 1980s, there has been high interest in branched-chain amino acids (BCAAs) by sports nutrition scientists. BCAAs consist of three aminos—leucine, isoleucine and valine—that are considered essential because the body cannot produce them by itself and they must be consumed in the diet. Athletes often take supplemental aminos because they play a role in protein metabolism in the muscles. If BCAA stores become depleted, fatigue and longer recovery from exercise can result. In reviewing the medical literature on BCAAs, scientists at the University of Pavia in Italy found that BCAA supplementation before and after exercise decreased exercise-induced muscle damage and promoted muscle-protein synthesis. In other recent works, they found that BCAAs are critical for manufacturing important cells and chemicals involved in the immune system. According to these findings, BCAAs are a useful supplement for muscle recovery and immune regulation for athletes.