Modifying children’s diets is a more effective cure for hyperactivity than powerful drugs that have to be taken in increasing doses and have no lasting effect, Professor Joseph Egger told the inaugural meeting of The Allergy Research Foundation. Sufferers could also end up with related problems such as alcoholism in adulthood, he said.

Brain activity in affected children who were treated at the University Children’s Hospital in Munich differed according to the food they ate, said Professor Egger.

After the conference, he called for work with hyperactive children to begin in the nursery. “Many parents notice their children are hyperactive very early on: babies don’t sleep very well. But most cases are picked up in kindergarten where children have to work in a group and they react with aggressive behaviour.

“If you give the drug, Ritalin, to these children in the morning, by lunchtime they will need it again and you have to increase the dose, which makes parents worry about addiction. If you stop at any time, the patient is not cured, and as an adult it will be as if you never treated them.

“The problem comes when the patient hits puberty, starts going out with his peer group and wants to drink cola or eat chocolate,” he said.

Dr Jonathan Brostoff, founder of the new charity, said a Bournemouth doctor had enrolled school nurses in a project aimed at picking up and treating hyperactive children early.

Researchers told the conference that problem behaviour was caused not only by reactions to food but by low levels of certain minerals. Dr Neil Ward of Surrey University said giving hyperactive children doses of the food colourings, Tartrazine and Sunset Yellow, lowered blood zinc levels and hugely increased the mineral in urine.

Zinc is already lower than normal in hyperactive children, and these changes coincided with the rapid onset of symptoms.

The conference heard that the majority of crime in Britain and the United States was committed by just 6 per cent of young adults, many of whom have been hyperactive, and dramatic reductions in crime rates could be made much more cheaply and effectively through knowledge of dietary research than by prison.

Professor Steven Schoenthaler of California State University said he had reduced anti-social behaviour among young prisoners in US jails by giving a simple multi-vitamin supplement daily.