(Memorize this word so you can impress all your friends at parties).  There is an important enzyme produced by the intestinal lining called dipeptidyl peptidase-IV , DPP-IV.  This enzyme is responsible for processing casein and gluten down into a form that can be absorbed harmlessly into the blood as a protein nutrient.  The problem with autistic children is that DPP-IV function has been compromised.  Therefore, the proteins are processed into a chemical form that causes an opiate-like reaction in the brain.  Those forms are called   gliadomorphins and caseomorphins.  Note the same root word as "morphine."  When these improperly digested proteins reach the brain it is like a hit of opium and the child feels good.  That is why so many autistic children restrict their diets to foods containing gluten and casein.  They are after what is called the "opiate effect."