Insulin is a protein that is digested in the intestinal tract.

胰岛素是一种在肠道中就被消化的蛋白质
That's one of the functions of our gut,

消化蛋白质也是肠道的一项功能
is to digest foods that we eat,

消化掉我们吃进去的食物
foods that contain proteins for example.

例如含有蛋白质的食物
So, your intestinal system is very efficient

所以说你的肠系统能够高效率地
at breaking down proteins into their constituent amino acids,

将蛋白质分解为它们的组分氨基酸
and it does that so that

那样做是为了
you can extract amino acids from food and use them for other things.

你能够从食物中提取氨基酸并留作他用
If a protein is a drug,

如果某种蛋白质是一种药
you need it to enter the bloodstream without being broken down.

你需要它进入血流但不能分解
When it's broken down it doesn't have the effect any longer.

当它分解后也就失去药效了
So, insulin can't be delivered orally,

所以说胰岛素不能口服