There are a great many dietary interventions that have proven helpful for children with autism. Simply "cleaning up the diet" from damaging substances such as pesticides, artificial ingredients, and excessive sugar can improve some children enormously. However, there are also more specific dietary interventions that may prove helpful for your child. A very good resource for finding out more about each of the dietary intervention options (including how to clean up the diet in general) is Nourishing Hope: Nutrition Intervention for Autism Spectrum Disorder, by Julie Matthews, a Certified Nutrition Consultant, and DAN! practitioner. A good diet should eliminate any substances that are harmful for a particular person (these can range from artificial colours, to corn, to tomatoes) and provide healthy, nutrient-dense foods that allow the body to grow, heal, and function optimally.