An explanation of why the GFCF diet may help autistic children.

The theory is that many if not all autistic children  have a damaged intestine/gut. The damage may be there from birth but more likely comes from some immunological  injury like a bad reaction to an immunization.  (keep in mind this is mostly theory). Autistic children seem to have weaker immune systems, and a lot seem to have digestive problems.

This "leaky gut" allows some food proteins to pass through into the bloodstream only partially digested, particularly the gluten from wheat/oats/rye/barley, and the casein from milk and other dairy products. These partially digested proteins form peptides which have an opiate-like affect (opioids is another term for them). They can bind to the receptors and cause harmful effects in the brain  just like a regular opiate. Opiates can either cause or magnify autistic symptoms. The opiates are a type of narcotic.  There are receptors in the brain that they bind with to reduce pain and induce pleasure, but they also have harmful side effects. An example of an opiate is morphine or heroin. Until it can be figured out how to heal the "leaky guts", many parents are putting their children on the gluten free/casein free diets .    
 
If you look at the available medical literature, there are at least three highly reputable sources for the benefits of removing certain dietary items (gluten and casein) from the diet of children with autism. In the studies of Cade*, Reichelt* and Shattock*, approximately 80% of autistics are significantly improved (not synonymous with cured) by the STRICT removal of gluten and casein.  A 100% gluten and casein free diet. Sorry, but 99% free doesn't count.  This means no: milk products, wheat, barley, oats, spelt or rye flours. (It is tough to do because most autistic children are fully addicted to the stuff - but there is enough emperic data and clinical observation to justify the one year trial). It has been found to take up to one year to remove all the caseomorphine and glaidomorphine from the body.  This is because of the blood reproduction and ability to breakdown and rid body of it.

Observe behavior during the wash out. Be aware that many family members and well intentioned friends or teachers have the idea that "just a little won't hurt". This is wrong and there is good data to support why this is true, but if you really want to know if this is what is making your child autistic, then you must really police this.