Essential amino acids, or EAAs, are amino acids that our body needs but cannot produce on its own, and there are 9 of them: Histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine.

基本氨基酸，简称 EAA，是我们身但不能自己产的氨基酸，其中有 9 ：氨酸，异亮氨酸，亮氨酸，赖氨酸，蛋氨酸，苯丙氨酸，苏氨酸，色氨酸和缬氨酸。

I would say that we do not add leucine alone because leucine, isoleucine, and valine go hand in hand.

我认为我们不会单独添加亮氨酸，因为亮氨酸、异亮氨酸和缬氨酸是相伴而行的。