There is much discussion among families about the relationship between nutrition and autism spectrum disorder (ASD). There are claims of diets that will "cure" ASD: gluten-free, casein-free, specific carbohydrate diet (SCD). There are claims of benefits by adding nutrients to the diet, such as vitamin B-6 and magnesium, vitamin B-12, or essential fatty acids. All of these possibilities can leave a parent wondering what to do. While there are many food-related issues for people with ASD, medication and nutrient interactions, and gastrointestinal problems, this article: (1) defines an "evidence-based" treatment; (2) gives tips on how to set up and evaluate any treatment plan for one's child; (3) summarizes some of the popular diets and supplements and how they claim to benefit those with ASD; and (4) examines how to evaluate some of the current nutritional theories.