Drinking several servings of soda a day is associated with behaviour problems such as aggression, a new study of preschoolers suggests.

When researchers looked at 2,929 children in the U.S., they found 43 per cent of parents said their child had at least one serving of soda a day and four per cent had four or more servings daily.

Four per cent of parents in the study reported their children had four or more servings of pop a day. Sugar and caffeine are potential triggers for behaviour, but parenting practices and home environment are also an influence. (Reuters)

"In this large sample of five-year-old urban U.S. children, we found strong and consistent relationships between soda consumption and a range of problem behaviours, consistent with the findings of previous studies in adolescents," Shakira Suglia of Columbia University's Mailman School of Public Health in New York and her coauthors concluded in Friday's issue of the Journal of Pediatrics.

Children who consumed four or more servings of soda per day were more than twice as likely to destroy things belonging to others, get into fights and physically attack people compared with children who drank no soda.

Drinking four servings of soft drinks was associated with increased aggressive behaviour, even after accounting for factors such as TV viewing, candy consumption, maternal depression and intimate partner violence.

The researchers noted they can't tell whether there is a cause-and-effect relationship between drinking pop and the behaviours.

The researchers didn't have information on the type of soda consumed, such as regular or diet or caffeinated or non-caffeinated. Both caffeine and sugar are potential mechanisms, Suglia said. Caffeine is associated with impulsivity in children and adolescents but the scientific evidence for sugar is mixed, she added.

Nutrition Prof. Katherine Gray-Donald of McGill University in Montreal said the study has merit, even though it doesn't prove anything.

"When we look at simply three groups of children eating low, medium and higher levels of sugar, you look at your nutrient intake, as the sugar goes up, the amount of many other nutrients just declines quite regularly," Gray-Donald said.

"We don't know if in a large population you may get children who are really missing some nutrients that are very important for their development. That's hard to say."

It's also possible that as much as the researchers tried to control for other things, they can't completely control for the home environment, such as parenting practices.

The Fragile Families and Child Wellbeing Study was funded by the U.S. National Institute of Child Health and Human Development.