Food Additive Chemistry

Chemistry World  takes a look at artificial food additives, as a study commissioned by the UK Food Standards Agency (FSA) suggests they may increase hyperactivity in children.

Which food additives were involved in the study?

Sunset yellow (E110), carmoisine (E122), ponceau 4R (E124), tartrazine (E102) and allura red (E129) are all azo compounds, containing the Ar-N=N-Ar group. The delocalisation of electrons around both aryl rings is responsible for the compounds’ absorption of visible light, making characteristic bright colours. Like the remaining food colouring involved in the study, quinoline yellow (E104), they are all synthetic dyes not existing in nature, and are added to food and drink to make it look appealing.

Sodium benzoate (E211), the sodium salt of benzoic acid, is a preservative which stops bacteria and fungi growing in food and drink. In acidic conditions, benzoic acid is absorbed into bacterial cells, and prevents anaerobic glucose fermentation, so blocking bacterial growth. The preservative is found in apples and some berries, and is widely added to drinks.

Haven’t they been safety-tested before?

Yes, all food additives have to be safety tested to receive an E number from the European Commission (EC). But some of these tests were conducted more than 20 years ago, and didn’t take into account the potential for neurotoxicity and developmental effects. So the European Food Safety Authority (EFSA) has been asked by the EC to re-evaluate all food additives. It is giving food colourings top priority, because their legislation is based on the oldest data. By the end of 2007, the EFSA expects to re-assess 45 food colourings.

Which food additives were to blame in this study?

Impossible to say, because the study only looked at six colourings and a preservative, and mixtures were always taken together. The researchers picked mixtures representative of children’s typical diet. Ideally additives would be tested individually but ’it is simply much more complicated, expensive, and less realistic to study each one individually on children,’ explained Diane Benford, a toxicologist working for the FSA.

Why might food additives worsen hyperactivity?

Nobody knows. The researchers didn’t suggest any biological mechanism. There was a huge variation in additive effects on children’s behaviour, so the researchers sampled their DNA, looking for related variants in genes already known to influence attention-deficit hyperactivity disorder (ADHD - a disorder with symptoms more extreme than those seen in the study).  They found a statistically significant association with genetic variants thought to impair the breakdown of histamine, though the differences weren’t strong enough to usefully pick out people at risk. Other suspect genetic variants, including those implicated with the neurotransmitter dopamine, weren’t found to correlate with children’s behaviour in this study.   

What happens next?

The FSA has informed their European counterparts about the study. An EFSA panel will assess the new findings at the end of September, as part of its ongoing re-evaluation of food additives. It is then up to the EC to make new regulations. This arrangement has already brought results: in July 2007, the EC banned the rarely used synthetic food colouring Red 2G (E128) following new EFSA recommendations. 

Suppose some of these additives were banned: are there any alternatives?

Yes, for the colourings. The artificial colourings are convenient to make and use in large-scale production, which is why they gained favour. But plenty of other colouring additives are found in plants - such as lycopene (in tomatoes) or beta-carotene (in carrots).  According to Richard Ratcliffe, executive secretary for the UK’s Food Additives and Ingredients Association, consumer pressure has meant that many large food manufacturers have already abandoned artificial colourings, regardless of scientific research. ’The tide has already gone out, and studies like these are left on the beach,’ he said. 

Because sodium benzoate is such a widespread and important preservative, removing it from drinks would likely harm public health more than it would help children’s behaviour. Potassium sorbate is one possible substitute, but more expensive and difficult to use, said Ratcliffe. 

Richard Van Noorden

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