Nearly everyone has always accepted the belief that sugar makes kids hyperactive; in fact it's so deeply ingrained that even some researchers have had trouble accepting their own results. In one study, 35 children reported by their mothers to be "behaviorally sugar sensitive" were separated into two groups. Half were told they were given a sugary drink, half were told it was a sugar-free drink. Then the mothers played with the children and were individually interviewed. Overwhelmingly, mothers who were told their child was given sugar rated their behavior as hyperactive. In fact, all children received the same sugar-free drink. In this case, the perceived affect was confirmation bias by the mothers — where they picked up only on cues that supported their pre-existing conviction.
Another similar study found that 50 children whose mothers "knew" that their children's behavior was worsened by sugar were given a blinded test where the children were given either sugary or a sugar-free drink, and then observed — but this time the mothers didn't know which was which. No differences between the groups could be ascertained over three separate trials. And the lack of an effect extends to classroom performance, too. 16 hyperactive boys were given controlled diets of either sugar drinks or sugar-free drinks at measured intervals throughout two school days and were regularly given behavioral and cognitive tests. Again, there was no difference in performance between the groups.
Biochemically, the claim doesn't make sense for normal healthy children. The amount of sugar in the blood is carefully regulated by insulin. Whether you eat a lot of sugar or none at all should make no difference to your blood sugar level.
February 27, 2009