Probably none. Most chidren, autistic or not, eat an adequate diet and do not require vitamns past the infancy period. If an autistic child does not eat a variety of foods, or eats alot of non-food items, then he might benefit from a multivitamin. Vitamins are not an appropriate treatment for autism.
Controversial . Some feel vitamins have no place in care of autistic kids. However, in light of how well our other treatments are working, it seems worth a try. An option: a physician mother of 3 autistic children developed a liquid vitamin called "agape." one of my patients did settle his episodic agitation. It's expensive, though. See for info & contents: http://www.Awakennutrition.Com/agape/about.Html.
So Far None. I agree that we need an open minded approach, but i would like to see research with proof of effectiveness.There is none.Individual "testimonials" are often biased and very few have turned out to help.See " lorenzo's oil" , a "cure " for a birth defect that was sworn to work, but did not.Megavitamin therapy is another such mishap.At present, nothing has been proven.