Food Additives Associated With ADHD Symptoms
May 27, 2004
Laurie Barclay, MD
Food additives are associated with symptoms of attention deficit hyperactivity disorder (ADHD), according to the results of a randomized trial published in the June issue of the Archives of Diseases in Childhood. The investigators suggest removing these from the diet of all children.
"There have been no population based studies examining the prevalence of hyperactivity related to intolerance to food additives following the initial claims of the detrimental effect of artificial additives on children's behaviour," write B. Bateman, from the University of Southampton in the U.K., and colleagues. "Subsequent studies, despite improved methodology, have failed to substantiate this claim or have only shown a small effect."
To determine whether artificial food coloring and preservatives in the diet influence hyperactive behavior in three-year-old children, a sample of 1,873 children were screened for the presence of hyperactivity at baseline. Skin prick tests to identify atopy were performed in 1,246 children.
After baseline testing, children were given a diet free of artificial colorings and benzoate preservatives for one week. For the next three weeks they received, in random order, periods of dietary challenge with a drink containing artificial colorings (20 mg daily) and sodium benzoate (45 mg daily), or a placebo mixture, in addition to their diet.
During the withdrawal phase, there were significant reductions in hyperactive behavior. Based on parental reports, there were significantly greater increases in hyperactive behavior when children were given the drink containing additives than when given the placebo drink. The presence or absence of hyperactivity or of atopy did not influence these effects. There were no significant differences detected based on objective behavioral testing in the clinic by a tester blind to dietary status.
"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," the authors write. "Subgroups are not made more vulnerable to this effect by their prior levels of hyperactivity or by atopy."
Study limitations include possible self-selection of families to take part in the food challenge, completion of all phases of the study by only 70% (277of 397) of those invited, and inability to demonstrate changes in hyperactivity on the basis of psychologist-administered tests. The authors recommend attempts at replication in other general population samples and extension of this study to older age groups.
"These findings therefore suggest that significant changes in children's hyperactive behaviour could be produced by the removal of artificial colourings and sodium benzoate from their diet," the authors conclude. "The potential long term public health benefit that might arise is indicated by the follow up studies which have shown that the young hyperactive child is at risk of continuing behavioural difficulties, including the transition to conduct disorder and educational difficulties."
The Food Standards Agency and the South West Regional Research and Development Directorate funded this study. Smith Kline Beecham contributed to the challenge materials.
Arch Dis Child. 2004;89:506-511