Avoid additives, but which ones?

Thursday September 6 2007

A Food Standards Agency (FSA) study has provided new evidence of a link between food additives and hyperactivity. The Daily Mail reports that “children’s foods can make them behave badly” and The Independent states that additives “cause hyperactivity among normal infants”.

Many newspapers report the guidance offered by the FSA that parents should avoid giving their children drinks and processed foods that contain the additives but they also suggest that more regulative controls are needed.

This research has been conducted in a range of normal children from the general population and not only in those already affected by hyperactivity. It is the highest level of evidence yet presented on this topic. However, it does not address some of the supplementary questions parents might ask, such as “which additives are responsible and should I avoid the preservative sodium benzoate as well?” As The Guardian suggests, this places “a huge burden on parents”.

The study concludes that food additives can exacerbate hyperactive behaviour in any child up to the age of nine.

Where did the story come from?

Donna McCann and colleagues from the University of Southampton and Imperial College London carried out this research. The study received funding from a Food Standards Agency grant and was published in the peer-reviewed medical journal, The Lancet .

What kind of scientific study was this?

This was a randomised, double-blinded, placebo controlled trial with a cross over design. The researchers recruited two age groups of children: 153 children aged 3 years and 144 children aged 8-9 years from preschools and schools in Southampton were enrolled in the study. Two mixes of additives were studied in comparison with a placebo, mix A and mix B, and each child was studied in a similar way.

Mix A contained 20 mg of artificial food colourings: sunset yellow (E110), carmoisine (E122), tartrazine (E102), ponceau 4R (E124) and 45 mg of sodium benzoate (E211), a preservative. Mix B contained 30 mg of different food colourings: sunset yellow, carmoisine, quinoline yellow (E110) and allura red AC (E129) and 45 mg of sodium benzoate. Doses were slightly higher in the mixes given to the older children.

At the start of the study all the children received a week of typical diet free from all additives. Then the mix drinks containing additives were introduced into the diet. Independent panels of young adults were used to test whether the drinks and the placebo could be told apart by appearance or taste and no differences were found.

Three commonly used measures of behaviour and attention were used to assess the children. These ratings scales were completed by parents or in the classroom. One was based on 8 minutes of observation three times a week. The 8-9 year old age group also took a computerised test of attention.

What were the results of the study?

The findings reported by the researchers include a “significant adverse effect of Mix A compared to placebo for all 3-year-olds, but not for Mix B versus placebo”. They also reported that “the analysis of 8 and 9-year-old children showed a significantly adverse effect of Mix A or Mix B compared to placebo”, but they acknowledge that this finding was true only when the analysis was restricted to children who consumed at least 85% of drinks, and when the results were analysed without taking into account the missing data.

What interpretations did the researchers draw from these results?

The researchers interpret these findings as showing that “artificial colours or a sodium benzoate preservative (or both) in the diet result in increased hyperactivity in 3-year-old and 8/9-year-old children in the general population”.

What does the NHS Knowledge Service make of this study?

This is a well-designed trial with results that are significant and others that border on statistical significance.

The evidence provided by this study suggests that food additives can be harmful to normal children. There are, however, some features of this study and its results which suggest a measured response is wise.

  • The effect on behaviour was small in comparison to the hyperactivity seen in children with ADHD (attention deficit hyperactivity disorder).
  • Only those children who completed the study were analysed and this may have introduced some bias in the results. The 30 children who dropped out of the study may have differed in some way from those who completed it.
  • The analyses presented were on the borderline of significance, in some cases, and these results need to be incorporated with the results of other studies in a systematic review of the evidence.
  • The precise additive that is responsible for the effects shown is not known.

In general, studies that report harms are useful, especially studies where the common sense suggests that avoiding additives in soft drinks and processed food would be prudent and a relatively easy personal choice to make.

The degree of proof required for bodies charged with regulating the food industry may be different and further research may be required to inform policy. In particular, the additives to concentrate on in more detail must be defined.

Sir Muir Gray adds...

We are surrounded by so many chemicals that it makes sense to minimise the number that we consume.

Analysis by Bazian
Edited by NHS Choices