this thread is interesting -

I can't take glutamine - it really messes my head up. I get out of balance VERY fast with the other amino acids like taurine if I take it continuously. I once took taurine for several days and started out great, then felt very flat and tired - the antidote was glutamine (these two aminos are opposing I think or share the same pathway in the brain).

But it seems to have a good effect on some.