Researchers at the Univerity of Liverpool studied the effects of food colouring brilliant blue (E133) combined with monosodium glutamate (MSG; E621) and colouring quinoline yellow (E951) combined with the sweetener aspartame (E951).
According to the report, published in the journal Toxicological Sciences, when these additives were combined in levels similar to those consumed in a typical children's snack and drink, they stunted the growth of nerve cells in mice, interfering with proper signalling functions.
The researchers revealed that the combination of brilliant blue and MSG could inhibit cell growth up to four times more than the additives on their own, while for quinoline yellow and aspartame the figure rises to seven.
In response to the study, UK regulatory body Food Standards Agency (FSA) said "all of the additives included in the study are permitted for use in food under current EU legislation following a rigorous safety assessment. The safety of all additives is kept under review."
However, the researchers note that "even though the use of single food additives at their regulated concentrations is believed to be relatively safe, their combined effects are unclear and until now have not been widely studied."
The three-year study was funded by Organix Brands, manufacturers of a range of organic foods for children.
"Many parents of sensitive children know that food additives are a problem. And in processed foods like sweets and snacks they are typically present in combinations," said Dr Lizzie Vann, founder of Organix Brands.
"Many parenting and campaigning groups have been calling for stricter regulation and more caution to be taken with additives. At last, the scientific support for their suspicions is beginning to appear," she added.
Indeed, in its statement the FSA also pointed out that it is funding research "to investigate possible effects of mixtures of chemicals, including food additives. The latest Agency call for research specifically requests proposals for research investigating the effects of exposure to multiple chemicals occurring in food."
"The Agency is also funding research on the effects of two groups of colour additives on the behaviour of 3-year old and 8-9-year old children. This is expected to report in spring 2007," it added.
The food colouring brilliant blue, which is currently banned in the majority of EU countries, is used in the UK in sweets, confectionery, dessert and edible ices, as well as in some soft drinks, baked goods and tinned processed peas.
Quinoline yellow is banned in foods in Australia, the US and Norway, but its applications in the UK include sweets, smoked haddock, confectionery and pickles.
MSG is banned in baby food in the UK, but is used in a variety of crisps and snacks, which, according to research cited by Organix, are consumed at least once a week by 60 per cent of under five year-olds.
The controversial sweetener aspartame is currently used in more than 6,000 food and drink products in the EU and as a table-top sweetener. But health concerns linked to the product have surrounded it with a stream of negative publicity.
According to Organix, "more needs to be done to understand the effects of additives, and in particular the effects of additives when mixed together."
"Babies and children are especially vulnerable to harm from toxic chemicals since they are at a crucial stage of development," it added, suggesting that "processed food and confectionery are probably the main two food types that should be avoided by children where possible."