Diet is often viewed today as both the cause and solution of behavioural problems. In Wales, free school breakfasts, the Appetite for Life report and Jamie Oliver have put children's diet on the political agenda, aiming to improve both health and behaviour. There are several reports on the effects of diet on children's behaviour.
Although there is increasing evidence that missing breakfast results in poorer mood, memory and attention, the nature of the meal has been largely overlooked.
Children at a Swansea school were filmed for a month recently after attending its breakfast club. Each day the meals differed in the speed with which they released glucose. After a meal of cheese and ham that released energy slowly, rather than processed cereal that released it quickly, pupils spent more time doing school work and memory and attention benefited. The meals provided in breakfast clubs are typically those leading to poorer performance.
One proposal in the Appetite for Life report was that the sale of cereal bars should be banned. Rarely do sweeping recommendations meet all requirements. A study carried out in Swansea University found that when nine-year-olds ate a muesli bar mid-morning, some spent more time performing their school work. Those who benefited from the snack had eaten a small breakfast. As up to a third of children choose not to eat breakfast, the provision of snacks may not be undesirable in some cases.
Although the education authority in County Durham is assessing the effects of Omega 3 fatty acid supplements on GCSE results, the Food Standards Agency (FSA) concluded that there is not enough evidence to say that they influenced children's education.
The Advertising Standards Authority told Dairy Crest to remove St Ivel Advance milk adverts that claimed the product could enhance children's learning ability. The Omega 3-containing "clever milk" had been advertised by Lord Robert Winston.
Similarly, there is little evidence that hyperactivity or dyslexia benefit from supplementation. However, half-a-dozen studies report decreased aggression following Omega 3 supplementation.
A recent Southampton study found that food additives caused temper tantrums and poor concentration. The FSA has asked food manufacturers to say which products contain these colourings, not to ban them but to allow informed choice. In fact, artificial colours have been replaced with those from natural sources for some time, for example, the demise of the blue Smartie reflects the lack of an alternative colouring.
Although there is growing evidence that certain artificial colourings and preservatives cause problems, it is unreasonable to assume that alternatives from natural sources are necessarily safe. Some of the deadliest chemicals are of natural origin. The Japanese puffer fish, a culinary delicacy after appropriate preparation, contains tetrodotoxin that is 1,200 times deadlier than cyanide. New additives of natural origin need to be tested.
The importance of considering natural foods is demonstrated by hyperactive children whose parents believe that they react to their diet. More than four dozen foods are a problem for some children and no child is sensitive to additives alone.
The problem foods, in declining importance, are cow's milk, chocolate, grapes, wheat, oranges, cow's cheese and hens eggs. The pattern of response differs from child to child and you cannot single out additives, or a particular food, as a unique or universal cause of problems.
Simple responses, such as removing a particular item from school meals, will not have a dramatic effect if it is only one problem among many.
Although there is increasing evidence that food can influence behaviour, children often need to be treated as individuals rather than as a group as their response is idiosyncratic. The effects are often subtle and maybe short term if other factors that influence behaviour are not also addressed.
David Benton is professor of psychology at Swansea University