Optimum Nutrition amino provides Essential Amino acids and combines the optimal ratio of rapidly absorbed free-form amino acids with natural energizers and N.O. boosting ingredients to help you reach your next level - including muscle-building BCAAs and arginine for more intense, vascular pumps. At 10 calories per serving, it'll make a big impression without denting your diet. Mix up Essential Amino Energy anytime you want to dial up mental focus, physical energy N.O. production and recovery support.