"Like many other treatments, the autism diet isn't scientifically proven to improve symptoms or help children recover from autism. So far, there's just a lot of anecdotal evidence from parents of autistic children. The diet usually requires excluding
gluten (a protein found in wheat) or
casein (a protein found in milk). Let's start with looking at why these substances -- found in so many foods and other products -- might exacerbate the symptoms of autism".
Discovery Health "What is the autism diet?"