The most favorite "alternative" diet for Asperger's, at least among parents, is probably the Gluten Free Casein Free (GFCF) Diet. This diet is based on the theory that people with Asperger's cannot easily digest gluten (an ingredient in most grains) or casein (an ingredient in dairy products). The undigested molecules, according to this theory, can aggravate their Asperger's symptoms. Based on this theory, many parents rid their homes of all grains containing gluten - including flour, cereal, pasta, pretzels, bread, and crackers - as well as all products containing casein - including milk, cheese, sour cream, pudding, yogurt, pudding, and dairy margarine.
Is there proof that the GFCF diet works? Researchers have found that undigested gluten and casein molecules do appear in the urine of children with Asperger's syndrome. Anecdotal reports from parents is positive, with some of them claiming that the GFCF diet "cured" their child's symptoms. But true studies on the diet seem to contradict each other, with some finding no improvements at all due to the diet, and others finding significant improvements in many children.