Food additive chemistry
11 April 2008
The UK Food Standards Agency (FSA) has recommended that UK manufacturers voluntarily remove six food colourings from their products by 2009 - and it is pushing for action at European level. The advice follows an FSA-commissioned Southampton University study, reported in The Lancet in September 2007, which suggested some artificial food additives might increase hyperactivity in children. Here, Chemistry World updates its previous look at food additives and the 2007 study.
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. 'These additives give colour to foods but nothing else,' says Deirdre Hutton, the chair of the FSA - which is why the agency felt it was sensible to remove them from food and drink products in the light of the study.
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) was 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.
Are all or only some food additives to blame?
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. This methodological problem is partly why the European Food Safety Authority (EFSA) concluded in March 2008 that 'the findings of the study could not be used as a basis for altering the acceptable daily intake of the respective food colours.' Ideally additives would be tested individually but 'it is simply much more complicated, expensive, and less realistic to study each one individually on children,' says 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.
What happens next?
There is no mandatory ban on the use of the food colourings following the FSA's recommendations, but it's likely that manufacturers will take note. 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. 'UK industry has already taken great strides to remove [these six] colours from food,' says Hutton. The EFSA is yet to adopt an official opinion on food additives following its review, but expects to by the end of the year. 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).
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, says Ratcliffe.
Richard Van Noorden
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D McCann et al, Lancet, 2007 (DOI:10.1016/S0140-6736(07)61306-3)
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