A cocktail of artificial colours and the commonly-used preservative sodium benzoate are linked to hyperactivity in children, according to a ground-breaking study published on Thursday by The Lancet.
The implications are far-reaching, say the investigators, who suggest that by vetting their child's diet, parents have a simple tool to help them tackle hyperactive behaviour.
Researchers at Southampton University in southern England recruited 153 local three-year-olds and 144 children aged eight or nine and assigned them to either of two groups.
One group received an ordinary fruit juice and the other was given a drink identical in look and taste that contained common commercial additives. Both drinks were supplied to parents in identical, sealed anonymous bottles.
The "additives" group itself was split into two batches.
Some children were given "Mix A," a drink which contained artificial colourings typically found in a couple of 56-gramme (two-ounce) bags of sweets.
Others were given "Mix B" which had a higher level of colourings, equivalent (in the dosage for the eight-year-olds) to consuming the additives in four such bags of sweets.
Both mixes had the same amount of sodium benzoate.
Before the six-week trial began, the researchers asked parents and teachers to assess the child for overactive, impulsive and inattentive behaviour -- the hallmarks of hyperactivity.
A third yardstick was given by trained observers (in fact, psychology graduates), who sat discreetly in the classrooms and noted each child's behaviour according to an international set of measures.