BCAA 1000 from Optimum Nutrition contains a potent balance of Branched chain aminos (L-Valine, L-Isoleucine, and L-Leucine) which are proven building blocks of muscle mass and size. Metabolized directly in the muscle, B.C.A.A.s, can improve nitrogen retention by sparing other amino acid groups for repair and rebuilding. Vitamin B-6 has been added for maximum absorption.