My kids are dairy free and we limit gluten, and i do notice differences in their behavior (usually they are more happy and throw less tantrums). However, they do not have autism. With that said, I used to work with children on the spectrum (PDD-NOS, Autism, Aspergers, ADD, ADHD, OCD, etc). Some parents had their kids on a gluten free diet and every once in a while if the child got fed some gluten on accident, it was VERY evident the next day through behavior and abilities. I recall thinking that something was off that day (but oblivious as to the reason why, diet never occurred to me until i started learning more), and then i would meet up with the parents to brief them about the session, and they would mention that they ate X food the day before (or some similar happening). It all made sense then! I firmly believe that going gluten free helped these children immensely.