The dyes used to colour foods such as cereal, ketchup and snacks may contribute to hyperactivity in some children, a U.S. advisory committee has heard.

The U.S. Food and Drug Administration started a two-day meeting Wednesday to weigh data on the link between dyes and the disorder.

On Thursday, the panel will recommend whether the regulator should change labelling for food additives, request more study, or do nothing.

The FDA has long said the dyes are safe.

The U.S. consumer advocacy group Center for Science in the Public Interest requested the meeting to review research on the effects of additives with the aim of banning Yellow 5, Red 40 and six other dyes.

"Dyes are often used to make junk food more attractive to young children or to simulate the presence of a healthful fruit or other natural ingredient," said Michael Jacobson, the group’s director. "Dyes would not be missed in the food supply except by the dye manufacturers."

The advocacy group is urging the FDA to put warning labels, noting a full ban would be difficult.

Concern about food dyes became prominent in the 1970s when pediatrician Dr. Ben Feingold claimed the colours were linked to hyperactive behaviour and proposed a diet eliminating them.

Elimination diet

Since then, it has been difficult to do high-quality placebo-control studies over a period of weeks to show the effectiveness of elimination diet, said Dr. Susan Jerrott of IWK Health Centre in Halifax.

The research suggests a small group of children with ADHD, perhaps 10 per cent, may be reactive to food dyes and artificial food, Jerrott said.

"It's really frustrating for parents," Jerrott said in an interview. "All I can say as a scientist and a clinician is, ‘Yup,  the research would say that overall its unlikely to be effective but there's nothing wrong with trying'" an elimination diet. 

"But do know that its at least worth finding out from the teacher if she's seen difference or he's seen a difference."

Parents may say they see a difference in their children after an elimination diet but they could be expecting to see one and there is no way to blind them to the foods. That makes it important to also look for feedback on how daycare providers and teachers perceive any differences in the same children. 

Health Canada's label changes

The jury is still out, Jerrott said, in that the research points to irritability and restlessness. Since those aren’t signs of attention deficit hyperactivity disorder, it makes her wonder whether some of the children might have been misdiagnosed with ADHD and may have an underlying food allergy or sensitivity, an area that she said needs more review.

Health Canada said Wednesday it is completing its review of comments received during a 2010 consultation on proposed improvements to labelling of food dyes.

 "Health Canada will use the input received from this early consultation in the development of the regulatory proposal to improve the labelling of colours used in prepackaged foods," the department said in an email.

"In the meantime, Health Canada is encouraging food manufacturers who do not already do so, to voluntarily declare food colours by their individual common names on prepackaged food labels."

With files from CBC's Pauline Dakin and The Associated Press