Hyperactivity/Foods. While there is some evidence to suggest that additives and preservatives (i.e., chemicals) in food do some harm, diet has not found to be directly causative to any behavioral or psychological syndrome.
Food additives? In 2007, research financed by britain’s food standards agency and published online by the british medical journal the lancet presented evidence that a mix of additives commonly found in children’s foods increases the mean level of hyperactivity. Researchers concluded that "the finding lends strong support for the case that food additives exacerbate hyperactive behavior at least into middle school.
Sugar not a cause, Caffeine may calm. A few children with adhd have an allergic or pharmacologically mediated behavior change with some dyes (e.g., tartrazine, quinolineyellow, sunset yellow, carmoisine, ponceau 4r, & allura red ) & sodium benzoate in foods & medicines. If a child is allergic to certain foods or dyes & behavior changes on exposure, an elimination diet is worthwhile. Diet doesn't cause adhd.