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 South-ampton 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. 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-gram bags of sweets. Others were given “Mix B” which had a higher level of colourings, equivalent  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. For the first week of the trial, the children followed their typical diet.

After that, sweets and drinks with additives were withdrawn, and parents were asked to substitute with the trial drink instead. The amount of the drink given to the child was in proportion to the amount of artificial colouring removed from their usual diet. The parents did not know whether the drink was Mix A, Mix B or the placebo.
Mix A had a “significantly adverse” effect on the three-year-olds, although Mix B made no difference. In the older children, both Mix A and Mix B had a strong effect.

“Overall, children who took the mix moved about 10 per cent closer to the definition of being hyperactive,” lead author Jim Stevenson, a professor of psychology at the university, told AFP.