Since the 1970s, the belief that sugar can trigger or exacerbate symptoms of hyperactivity has been widespread. What does the research say about this belief?
Investigators from the Vanderbilt University Child-Development Center conducted a meta-analysis of 23 studies examining the effects of sugar on behavior and cognitive performance. To be included in the analysis, the studies had to have both an experimental group that consumed a known quantity of sugar and a placebo condition. In all of the studies, the subjects, parents and research staff were blind to the conditions. The conclusion, reported in JAMA (1995), was that consumption of sugar had no effects on behavior or cognitive performance.
Some might object that aspartame was used in the placebo conditions and that aspartame might trigger behavior and cognitive difficulties similar to the effects of sugar. But in a study that looked at the effects of extended use of sugar and aspartame, researchers found that neither one showed effects on behavioral or cognitive functioning in any of the 39 measures employed in the study.
So what gives? Why do so many parents insist that their children get cranked when they consume sugar?
Daniel Hoover and Richard Milich (J of Abnormal Psychology, Vol 22, August 1994) conducted an experiment that points to an explanation. They looked at 35 children who were reported to be sugar-sensitive by their mothers. The children were randomly assigned to an experimental group and a control group. Mothers of the children in the experimental group were told that their children received a large dose of sugar. Mothers of children in the control group were told that their children received a placebo. Actually, none of the children were given sugar. All were given a placebo. Interactions between mothers and children in both groups were videotaped and the mothers rated the interactions.
Hoover and Milich found that the mothers who thought their children consumed sugar rated their children as significantly more hyperactive than the mothers who thought their children had received the placebo. Moreover, review of the videotapes showed that the mothers who were told that their children received sugar behaved differently from the mothers who were told that their children were given a placebo. The mothers in the sugar-expectancy condition looked at their children more, stayed physically closer to their children, criticized their children more and talked more to their children. In other words, when the mothers believed that their children consumed sugar, they behaved as if their children were in need of greater supervision.