Most special diets provide the same benefits for autistic people as they do to people who are not autistic. They do not appear to provide any additional benefits to autistic people, according to a limited amount of research evidence of sufficiently high quality.
No evidence at all supports the use of most special diets (such as additive-free diets, the specific-carbohydrate diet, and the yeast-free diet).
Determining the benefits of other diets (such as the gluten-free, casein-free diet or the ketogenic diet) for autistic people is not currently possible. We must wait until further research of sufficiently high quality has been completed.