The belief that sugar and candy cause hyperactive, noisy or defiant behavior in children is so widespread that many parents accept it as a proven fact. While it makes sense to avoid giving kids too much sugar for health reasons, there is actually no proven connection between sweet treats and bad behavior.
The Mythical Sugar High
When kids start to play noisily or act out of control after eating sweets, parents are usually quick to name the sugar as the source of the problem. According to an interview with cognitive scientist Daniel Willingham in the Washington Post, there have been more than 12 studies pertaining to the effects of sugar on children's behavior, and none of them have found any connection. When parents believe their kids have had sugar, they usually describe the behavior as being worse than when they know the treats were artificially sweetened. In reality, studies have shown that children don't seem to behave any differently after eating sugar.
The University of Virginia School of Special Education describes a study in which a number of families ate a diet controlled and monitored by the researchers to test the effects of sugar. Sugar was added to some meals and not others without the families being told. When neither parents nor children knew if sugar was present in the meal, no behavior changes were observed by the researchers or the parents. According to the study, when the parents weren't told their kids had eaten sugar, they didn't notice any increase in hyperactive or defiant behavior.
Some parents believe that sugar has a particularly bad effect on children diagnosed with attention deficit hyperactivity disorder or ADHD. Parents of kids with ADHD may limit the amount of sugar their children are allowed to have to avoid triggering the ADHD symptoms. According to the National Institute of Mental Health, children with ADHD show no differences in behavior after consuming sugar. Even children whose mothers believed them to be particularly sensitive to sugar showed no behavior differences when tested.
Daniel Willingham notes that parents may be interpreting the behavior of their children as being worse than it really is due to their own belief in the negative effects of sugar. However, there may be other explanations for the hyperactive behavior associated with treats. The Virginia School of Special Education states that many candies are made of chocolate, and the caffeine in chocolate can definitely contribute to hyperactivity. Another possibility is that kids may act hyperactive for other reasons in situations where they also get treats. If friends come over for a visit, parents often serve treats. When the children get excited about their company and start playing noisily or acting defiant, parents may jump to the conclusion that the sugar is the cause.