Expired protein? Can I still drink it?

Happyme2009

Hi, since I haven't exercised last year I forgot I had 2 huge buckets of whey protein powder, one chocolate one vanilla... the vanilla is expired since Nov. 2011 and the chocolate Jan. 2012....
Today I drank one vanilla, it tasted fine to me.
Is it a problem if I still use them? Can I get sick from them? Do they really lose efficiency? I feel weird throwing them out, they were expensive when I bought them.....