"If you look at the peer-reviewed evidence, we cannot say sugar absolutely makes kids hyper; however, you can't discount that sugar may have a slight effect" on behavior, said Kristi L. King, senior pediatric dietitian at Texas Children's Hospital and spokeswoman for the Academy of Nutrition and Dietetics.

In the 1900s, an analysis reviewed around 16 studies about the effects of sugar in children. The research that was published in the medical journal JAMA, concluded that sugar does not have any effect on the cognitive performance or in the behavior of children. "However, a small effect of sugar or effects on subsets of children cannot be ruled out," the article said.

Like adults, some kids may be more sensitive to blood sugar rise than other kids their age. This could mean that they are more likely to become active when they consume sugar.

A small percentage of kids with attention-deficit hyperactivity disorder may be sensitive to sugar and their overall behavior may change when they consume it, according to Jill Castle, a registered childhood nutrition expert and dietitian who teaches parenting course called the ADHD Diet for Kids. "They may become more aggressive or hyperactive or difficult to parent," Castle explained.  Reducing sugar in their overall diet can be beneficial for these kids.

According to Castle, foods with lots of sugar can be equivalent to elevated amounts of artificial flavors, food dyes or other additives that could be very problematic for a child diagnosed with ADHD. It makes it difficult to figure out of sugar is the reason behind the behavior.

Researchers do not have a way to know whether there is a link to sugar and ADHD on kids, and it complicates the issue. "Is there a biomarker? A hormone level?" King asked. "It's disheartening for parents. ... They want answers. And unfortunately, nutrition is such an individual thing."

In one study from 1990s showed researchers gave kids a drink that contains a sugar substitute. One group of parents was told that their kids consumed a drink with high-sugar content, the other group was told the truth. Parents who were told that their kids had high sugar intake said their kids were more hyperactive, even though they did not take any sugar.

"Just thinking their children were consuming sugar caused moms to perceive their children as being more hyperactive," King said.

"When children consume sugar, it's usually around something fun: holidays, birthdays, celebrations; there's already that excitement there," she said. "I don't think you can say the sugar made them run around and play with friends. ... That would be very hard to separate out."