Hi (sorry about my english, I am mexican):
We put our son on a Gluten free and lactose free diet and he has changed a lot for good. He stoped crying for nothing and his behavior improved a lot. Our son Rogelio developed regression autism around his first year of age, and mi wife and I believe that it is very much related to the one year vaccine (measles, mumps and something else). We complement his nutrition with suplements (a lot of them such as omega, vitamines C, B12, B6, liver fish oil, GABA, Zinc, etc) and we were surprised recently when we needed a blood test of him for a surgery he needed; His results were awesome, everything was on the best levels for a 4 year old boy (hemoglobine, red globules, white globules, plates, the times for coagulation of blood, etc), even the doctors were impressed knowing he doesn't eat a lot of healthy food like: milk, bread, fruits, vegetables, etc.
I will really recomend you to try a diet, but first do a full study of hair, urine and blood, I will suggest "Great Plains Laboratory in Kansas", so you can see which kind of food or meals are not good for your son, and look at the levels of metals in his/her body, so you can guess which things are good and which ones don't. Also they give you a list of food that may be no good for him or her. If you need more info, please post another reply and I will send more info. I hope this has been helpfull.