Protein power?

FocusPlease

I just noticed i still have a container of protein powder (got shoved to the back of the pantry), but it has an "enjoy by" date on it. Do i really have to throw it out? Does it actually spoil, or does it simply breakdown and lose some of its effectiveness? Is it harmful to take it after the date? It's still half full, so I'd hate to throw it out, if I don't really have to. (It's a low glycemic version, geared toward women)

Thanks!
L.