I recently read an article in Fighters Only that said GSP takes whey protein after his workouts and also takes lots of fish oil. thats it, not even a multi. obvioulsy the minimalist approach is working for him. You know he is a hard ass worker though.
there was another fighter whom I have forgottten that said he only takes a multivitamin. Damn, i forgot who it was but it was a big name.
both of these guys are still young though, just throwing that out there.