Food colourings and preservatives—allergy and hyperactivity

The results of Bateman and colleagues' study5 are surprising. Indeed, hyperactivity decreased in children on a diet without artificial food colourings and benzoate preservatives, and increased following re-introduction. The effect was reported only by the parents, whereas no difference was seen based on objective psychological testing. Although the authors claim that their results are sufficiently strong to suggest a benefit from the diet, we question this statement. Parents reported improvement during both placebo and active challenge, independently of their order, and heightened hyperactivity during the washout week. However, the parents' observations can be easily explained by their expectations, which could lead to a biased assessment. The small difference between the active and placebo weeks, in favour of active challenge, is, in our opinion, not sufficient to recommend dietary treatment. Bateman and colleagues' study was not designed to explore a possible food allergy as a cause of hyperactivity. As the authors state, the results only show that atopic children are not over-represented in the group of children benefiting from the diet.