A few facts: As I discuss in ADHD: The High Price Of A Quick, Quick Fix, stimulant medication (the primary treatment for ADHD) sales are now five times what they were in 2002—with revenues exceeding $8 billion per year. 3.5 million children are presently on ADHD medication, compared to 600,000 in 1990.
Numerous studies have looked at the relationship between refined sugar and ADHD. Most indicate sugar does not play a role, while parents in the trenches with children bouncing off the walls often disagree.
Arguably, one of the most influential studies indicating that sugar plays no role in ADHD was published in 1985 by Dr. Mark Wolraich, which looked at 16 hyperactive boys over three days. On day one, learning was monitored in order to achieve a baseline. The boys were then either given a sucrose 1.75 mg/kg or a placebo drink at different times during the following two days. The test revealed no difference between the boys' behavioral or cognitive actions, whether they drank sucrose or placebo. Critics emphasized the study was in an artificial setting, thus not representative of the real world.
In another study, children considered sensitive to sugar were given aspartame, a sugar substitute. Although all the children were given aspartame, half their mothers were told their children were given sugar, and the other half were told their children were given aspartame. The mothers who thought their children received sugar rated them as more hyperactive than the controls and were more critical of their behavior, compared to mothers who thought their children received aspartame. It's a popular belief that refined sugar causes ADHD or makes symptoms worse and this bias is clearly indicated here.
The fact is that some ADHD (as well as non-ADHD) individuals may become hyperactive after ingesting refined sugar, but this is not the norm. Perhaps some children are “sugar sensitive,” but these would be isolated cases, not reflective of the general population.
OK, so sugar may not cause/worsen ADHD in general, but you can conduct a test to determine if sugar affects your child's behavior. For a week, allow your child to consume sugar and monitor his behavior, and keep a written log. Then, remove the sugar from his diet for a week. Then repeat so you have a total of four weeks of data and compare the results. This is simple but effective.
Finally remember that no matter the effect on an individual’s behavior, ingesting refined sugar is not healthy. From cavities to suppressing the immune system, to taking the place of healthy foods, to increasing the risk of diabetes, to obesity, it's well known that too much sugar can cause a range of health problems, even if ADHD is not an issue.