The effects of a double blind, placebo controlled, artificial food colourings and benzoate preservative challenge on hyperactivity in a general population sample of preschool children

Abstract:

Aims: To determine whether artificial food colourings and a preservative in the diet of 3 year old children in the general population influence hyperactive behaviour.

Methods: A sample of 1873 children were screened in their fourth year for the presence of hyperactivity at baseline (HA), of whom 1246 had skin prick tests to identify atopy (AT). Children were selected to form the following groups: HA/AT, not-HA/AT, HA/not-AT, and not-HA/not-AT (n = 277). After baseline assessment, children were subjected to a diet eliminating artificial colourings and benzoate preservatives for one week; in the subsequent three week within subject double blind crossover study they received, in random order, periods of dietary challenge with a drink containing artificial colourings (20 mg daily) and sodium benzoate (45 mg daily) (active period), or a placebo mixture, supplementary to their diet. Behaviour was assessed by a tester blind to dietary status and by parents’ ratings.

Results: There were significant reductions in hyperactive behaviour during the withdrawal phase. Furthermore, there were significantly greater increases in hyperactive behaviour during the active than the placebo period based on parental reports. These effects were not influenced by the presence or absence of hyperactivity, nor by the presence or absence of atopy. There were no significant differences detected based on objective testing in the clinic.

Conclusions: There is a general adverse effect of artificial food colouring and benzoate preservatives on the behaviour of 3 year old children which is detectable by parents but not by a simple clinic assessment. Subgroups are not made more vulnerable to this effect by their prior levels of hyperactivity or by atopy.

NON-TECHNICAL SUMMARY

This is the largest controlled trial to date investigating the effects of certain artificial food additives on children's behaviour. It was originally commissioned by the UK Ministry for Agriculture Fisheries and Food (MAFF), and then taken on by the Food Standards Agency (FSA).

The study involved 3-year-old children from a geographically defined population (the Isle of Wight). 1873 children were initially screened carefully in order to yield a final sample of 277 with 4 subgroups: children with ADHD/hyperactivity, children with allergies, children with both, and children with neither of these conditions.

The researchers tested a mixture of artificial food colourings (AFCs) along with one common preservative (sodium benzoate). First, parents were given specialist help to remove these particular additives from their children's diets for a month. Then - in the crucial 'double-blind challenge' phase - the children were each given a daily fruit drink for a week. Half of the children were given drinks containing the additive 'cocktail'. The others received a similar drink without them - but no-one knew which children were getting the additives.

The children's behaviour was rated before and after this 'challenge' by their parents, and also with some simple clinical assessments (involving computer games designed to assess inattention or impulsivity).

Results showed clear detrimental effects of the food additives (versus placebo) on children's behaviour, according to parents' ratings. These effects were not specific to any of the subgroups, but applied to the whole sample of 3-year-olds. The simple clinical tests revealed no effects of the additives.