The necessity of artificial additives in foods means they will continue to be despite being found to have adverse effects on behaviour, says a nutritionist.
In her article, published in the latest edition of the British Nutrition Foundation's Nutrition Bulletin, Claire Williamson reviews landmark studies on preservatives and the industry's response to the findings.
"Additives carry out a variety of useful functions and play a key role in maintaining the food qualities and characteristics that consumers demand, but are particularly important in keeping food safe," said Williamson.
"So some additives, particularly preservatives (including sodium benzoate) are necessary and probably here to stay."
While studies have found negative effects of food additives, most recently the Southampton study that linked some colourings to hyperactivity in children, Williamson said the effects of removing them altogether could be much worse.
All food additives must appear on food labels, either by name or an E-number, which means it has been approved for its intended use across the European Union.
Williamson wrote: "Food additives are not a new phenomenon and some have been around for centuries, e.g. baking powder (bicarbonate of soda) which has been in use since the 19th century and vinegar (acetic acid) which is used to preserve foods and prevent microbial damage.
"Some additives are found naturally in foods, such as vitamin E, which acts as an antioxidant and prevents fats from going rancid."
The European Food Safety Authority (EFSA) has formed a group to provide the European Commission with scientific advice on additives.
Meanwhile, following the Committee on Toxicity of Chemicals in Food, Consumer Products and the Environment's (COT) re-evaluation of their safety, the UK Food Standards Agency (FSA) has advised parents to prevent their child from consuming certain additives if they show signs of hyperactivity.
Some food manufacturers have reformulated their products to remove such additives, such as Nestle Rowntree, which removed additives from all its products in 2005.
However, Williamson said: "Whereas it may be possible to remove some additives from foods, preservatives are necessary because without them, food would quickly spoil.
"Benzoic acid, which is found naturally in cranberries, bilberries, plums, cloves and cinnamon, is added to processed foods to prevent the growth of microbes, particularly pathogenic moulds and fungi. As John Emsley, a chemical scientist, comments on the Sense About Science website, if this preservative was removed from food products, there could be an increase in the number of cases of food poisoning."
The Southampton study
The study at the centre of the debate was conducted in two phases. In stage one, 153 three-year-olds and 144 eight- and nine-year-olds were given one of two drink mixes containing artificial food colours and additives, or a placebo.
The children were drawn from the general population and across a range of hyperactivity and ADHD (attention deficit hyperactivity disorder) severities.
Mix A contained sunset yellow (E110), tartrazine (E102), carmoisine (E122), ponceau 4R (E124) and sodium benzoate (E211). This same mix was used in an earlier study on a cohort of three-year-olds which was deemed inconclusive because the effects were not confirmed by clinicians.
Mix B contained sunset yellow (E110), quinoline yellow (E104), carmoisine (E122), allura red (E129) and sodium benzoate (E211).
Phase one lasted six weeks, with every child consuming the mixes and the placebo for one week each, and a one week wash-out period between each. Parents were asked to keep other sources of artificial colours out of the diet, and to keep a diary of violations.
Phase two involved some of the children from the older group - responders and non-responders - during two half-day session a week apart, at which they were given either a placebo or an active drink similar to mix A or B, but the whole day's dose was given at once.
The effects on the children's behaviour were assessed using a global hyperactivity aggregate (GHA) based on aggregated scores of observed behaviours and ratings by teachers and parents, plus, for those aged eight and nine, a computerised test of attention.
The conclusions drawn by the researchers were that artificial food colours and additives were seen to exacerbate hyperactive behaviour in children at least up to middle childhood.
According to Williamson: "The lack of any possible biological mechanism means that it is not possible to conclude that the association is causal, and further research is needed to elucidate the individual effects of the specific additives used in the study."