Most special diets provide the same benefits for people on the autism spectrum as they do to people who are not on the autism spectrum. They do not appear to provide any additional benefits to people on the autism spectrum, 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 people on the autism spectrum is not currently possible. We must wait until further research of sufficiently high quality has been completed.