I'd like to stress how important it is to be patient on our way to recovering our children from autism. Often parents adopt the right diet, but if they do not see obvious results in 3 to 4 weeks, they stop it, and say "it's not working".
Please be aware that a good diet is working even if it isn't visible to us, and some children need more time than others. That's where we have to be patient - and not to give up easily.
We were very fortunate that when we started eliminating gluten from our son's diet, we saw changes within ten days. Before that, he was hyperactive and would always be on the go - walking or running back and forth. Then during the diet, he began to sit down and start focusing more. That was a proof for us, that the diet makes sense, and it encouraged us to eliminate other food groups from his diet.
He didn't react the same way when we started to eliminate casein, and sugar, etc. But we understood that he was benefiting from the diet regardless of obvious visible improvements. Slowly our entire family adopted our son's diet, so now we can see and feel the benefits of the healthy diet ourselves too.
I am convinced that without the diet and healing our son's gut, his recovery from autism would not be possible.
It takes a long time to get used to the diet change, but it's worth it. Please be patient with your child and give it a go.