Preservatives and food colours may be the culprits in ADHD

The suspicion that additives such as preservatives and artificial food colours can contribute to hyperactive behaviour in children has been around for years.

Many parents and teachers battling to cope with children classed as hyperactive believe that foods and drinks containing additives have a negative affect on some children's behaviour which in turn can affect their ability to learn.

The issue is controversial with experts offering at times opposing views.

Now a clinical trial where food colours and preservatives were removed from the diets of hyperactive children is suggesting that this should be considered as a standard part of the treatment for such disorders.

Professor Andrew Kemp from the University of Sydney says despite a substantial body of evidence which demonstrates the link between attention deficit hyperactivity disorder (ADHD) and artificial food colourings and preservatives, removing them from children's diets is still considered as an alternative rather than a standard treatment for ADHD.

Professor Kemp says of the three main treatments for ADHD in children, medication, behavioural therapy, and dietary modification, only drugs and dietary modification are supported by scientific data.

However, says Kemp, behavioural therapy, which has no scientific evidence base, is still thought of as necessary for "adequate treatment".

Professor Kemp questions why, despite evidence to the contrary, that the removal of food additives remains an alternative rather than a standard part of treatment for ADHD.

He says the use of alternative medicine is widespread - up to 50% of children attending tertiary children's hospitals in the UK and Australia have used it in the past year.

Professor Kemp says research published last year showed that children who were not hyperactive were significantly more hyperactive after they ate a mixture of food colourings and a preservative (sodium benzoate), and this clearly has implications for children with ADHD.

That trial involved 297 British children from the general population who were either age 3 or between the ages of 8 and 9 and whose diets were closely controlled for six weeks.

For the study the children drank either beverages with food additives or a placebo drink with no additives and neither the children nor the researchers knew which beverage the children were getting.

This prompted the European Food Safety Authority (EFSA) to review the evidence from 22 studies between 1975 and 1994 along with two additional meta-analyses which linked preservatives and colourings with hyperactive behaviours.

The EFSA review found that 16 of the studies reported that dietary modification had a positive impact on at least some children with ADHD.

Powerful stimulant medications such as Ritalin and Adderall are the most commonly prescribed treatments for hyperactivity and increasing numbers of children are being prescribed them.

However Professor Kemp suggests the harmless intervention of eliminating colourings and preservatives, should be part of standard treatment for children, before drugs are prescribed.

In February, the American Academy of Pediatrics also cited the same study as evidence that it is time to re-examine the issue.

Professor Kemp's remarks are published as an editorial in the British Medical Journal.