New research on common food additives, including the controversial sweetener aspartame and food colourings, suggests they may interact to interfere with the development of the nervous system.
Researchers at the University of Liverpool examined the toxic effects on nerve cells in the laboratory of using a combination of four common food additives - aspartame, monosodium glutamate (MSG) and the artificial colourings brilliant blue and quinoline yellow. The findings of their two-year study were published last week in the journal Toxicological Sciences.
The Liverpool team reported that when mouse nerve cells were exposed to MSG and brilliant blue or aspartame and quinoline yellow in laboratory conditions, combined in concentrations that theoretically reflect the compound that enters the bloodstream after a typical children's snack and drink, the additives stopped the nerve cells growing and interfered with proper signalling systems.
The mixtures of the additives had a much more potent effect on nerve cells than each additive on its own.
The study reported that the effect on cells could be up to four times greater when brilliant blue and MSG were combined, and up to seven times greater when quinoline yellow and aspartame were combined, than when the additives were applied on their own. "The results indicate that both combinations are potentially more toxic than might be predicted from the sum of their individual compounds," the researchers concluded.
The tests used are the same as those applied when testing combinations of pesticides for toxicity. "They are recognised as predictive of developmental outcomes in humans," said Vyvyan Howard, a toxicopathologist and expert in foetal development who led the study.
Exposure to food additives during a child's development has been associated with behavioural problems such as attention deficit hyperactivity disorder.
Additives are licensed for use one at a time, but the study's authors believe that examining their effect in combinations gives a more accurate picture of how they are consumed in the modern diet.
"Although the use of single food additives is believed to be relatively safe in terms of development of the nervous system, their combined effects are unclear," Professor Howard said. "We think there are signs that when you mix additives, the effect might be worse."
The colours used in the research are synthetic dyes certified as safe food additives in the EU. However, brilliant blue (E133) has been banned in several European countries in the past. Quinoline yellow (E104) is banned in foods in Australia, Norway and the US. Previous research has shown that MSG (E621) and aspartic acid, one of the breakdown compounds in aspartame (E951), are neurotoxins, according to the authors of the study.
Brilliant blue is found in sweets, some processed peas, some soft drinks and some confectionery, desserts and ices. Quinoline yellow is found in some smoked haddock, some confectionery and some pickles. MSG, which is banned in foods for young children, is found in some pasta with sauce products, a large number of crisps, processed cheese, and prepared meals. Aspartame is found in diet drinks, some sweets, desserts and medicines.
The Food Standards Agency said it would need further details and clarification on the research before making a full assessment. "All of the additives included in the study are permitted for use in food under current EU legislation following a rigorous safety assessment," it said in a statement. The agency added it was funding research on the effects of mixtures of colourings on children's behaviour and kept the safety of additives under review.
Speaking for manufacturers, the Food and Drink Federation said the additives in the study had all been approved as safe by the EU's expert scientific committee.
The Aspartame Information Service, which represents the sweetener industry, dismissed the research, saying that it "did not provide any meaningful information" because it exposed mouse cells in the laboratory to undigested aspartame. "When we consume aspartame it is broken down in the digestive system to common dietary components. Aspartame has been in safe use for 25 years and has been reviewed and approved by more than 130 countries," it said.
Roger Williams, a UK Member of Parliament, has called for emergency action to ban the artificial sweetener Aspartame (aspartamine), questioning its safety. The MP said that there was "compelling and reliable evidence for this carcinogenic substance to be banned from the UK food and drinks market altogether."

Reservations of some U.S. Food and Drug Administration scientists about the safety of Aspartame were overridden when the agency initially approved the food additive in 1981, but many other countries followed the U.S. lead in endorsing the chemical sweetener for general public use. Aspartame has been linked in various studies cited by Mr. Williams to brain tumors, anxiety attacks, neurological impairment and other side effects, particularly in experimental animals; however, several reviews by government agencies have found no credible proof of such risk to humans and no country has banned or limited the substance for human consumption and such non-governmental groups as the American Cancer Society and the American Heart Association assert that extensive investigation has not shown any serious adverse effects attributable to Aspartame. Nonetheless, organized groups continue to debate the issue vigorously and there are calls for class action law suits. The initiative by MP Roger Williams may now bring the debate into the open political arena of the House of Commons.

New research on combining Aspartame with other common food additives suggests that while each substance alone may be safe enough, some combinations frequently found in commercial products interfere with the development and function of the nervous system in rats. (Lau, et al.) Few, if any, other experiments with combinations have been conducted. On the other hand, surveys of human populations, which consume Aspartame in various combinations with artificial colorings and flavorings, have failed to convincingly show significant harm.

Aspartame is sold under the brand names of Equal, Nutrasweet and Canderel and is an ingredient of thousands of "diet" or "lite" products.