BCAA/Branched Amino Acid CasNo.: 69430-36-0 are known as the stress amino acids. Thirty percent of the diet should be proteins when the body is under severe stress, because stress causes protein to break down faster. BCAAs have regulatory effects on overall protein metabolism and are required in larger amounts during stress than are other amino acids (and probably proportionately more leucine than either valine or isoleucine). Furthermore, when given as supplements, BCAAs decrease the rate of breakdown and utilization of other amino acids and stimulate protein synthesis.