Food and mood
26 June 2003
Sarah Wellard investigates the latest evidence on how diet, additives and pesticides affect young people's behaviour.
It may not be just young people's physical health that is at risk from a diet that is high in saturated fats, sugar and salt and low in essential nutrients. There is growing evidence that, for some children, behaviour and learning capacity are being compromised as well.
Research published last year in the British Journal of Psychiatry on the benefits for young offenders of taking dietary supplements provides compelling evidence of links between inadequate diet and violent behaviour. Two hundred and thirty young offenders took part in a random controlled trial over 18 months, with half the participants receiving supplements of vitamins, minerals and essential fatty acids and half receiving placebos (dummy capsules which looked identical to those containing the supplements). The group taking the supplement committed 40 per cent fewer violent offences than the control group on the placebo, and there was a 25 per cent reduction in offending.
A striking feature of the study is that although balanced meals were available within the institution, prisoners' food diaries revealed that they were choosing unhealthy options and supplementing the meals with sugary drinks and snacks. The nutritional supplements were aimed merely at correcting the inadequacy of participants' diets. Research by the Consumers' Association found alarming parallels in the diets of children eating school meals. Although healthy options were listed on the menu, children's food diaries showed that they too reject the fruit and vegetables on offer and opt for fatty and sugary foods instead.
So can we conclude that similar results would be found if the participants had been children and young people living with their families? Bernard Gesch, author of the study and senior research scientist in physiology at Oxford University, points out that nutrients are crucial ingredients in the biochemical processes that produce brain neurotransmitters like serotonin and dopamine which are known to affect mood. He adds: "The study did take place in a prison regime but since every one of us needs these nutrients there is every reason to think it may also reduce offending in the community where poor diets are consumed. We tend to forget that humans are physical as well as psychological beings and putting poor fuel into the brain seems significantly to affect social behaviour."
Gesch's research does not explore whether all or just some of the dietary supplements are linked with a reduction in offending behaviour. And it does not indicate whether we are all predisposed towards bad behaviour from a nutritionally poor diet, or whether some people are more at risk.
Another area of research, into links between diet and some of the behavioural and learning problems associated with dyslexia, dyspraxia and attention deficit hyperactivity disorder (ADHD), may provide part of the answer.
Dr Alexandra Richardson, senior research fellow in physiology at Imperial College School of Medicine and at Oxford University, found benefits for children with information processing difficulties of taking omega 3 supplements, the fatty acid found most commonly in oily fish such as mackerel, sardines and salmon. She says: "These fatty acids are utterly crucial to human health and especially to the brain but they have just about disappeared from our diets." She believes that a wide range of conditions where brain and behaviour are involved can be improved with fish oils. "Depression is an omega 3 depletion syndrome. Controlled trials show that symptoms can be reduced by treatment with the omega 3 fatty acid EPA."
Richardson is currently collating the findings of her latest study, with 120 dyspraxic children in Durham, who are taking either a fatty acid supplement or a placebo. So far the results are very promising. However, she does not suggest that all children with ADHD, dyslexia or dyspraxia will benefit from fatty acid supplements, and emphasises that dietary or metabolic deficiency is only one factor in these complex conditions.
Food additives are another area of concern in the diet and behaviour debate. For decades parents of small children, and especially parents of children with ADHD, have been concerned that some additives may be triggering, or at least contributing to poor concentration, over-activity and mood swings.
The Food Standard Agency (FSA), the government's food watchdog, commissioned its own research into the effects of certain additives on children's behaviour, but the study was deemed by experts to be methodologically flawed. A spokesperson for the commission explains: "There were problems in the way the research was set up. It didn't separate the effects of known stimulants such as caffeine and sugar with the possible effects of food additives." The FSA is now commissioning new research.
Kath Dalmeny, research officer at the Food Commission, an independent food campaigning organisation, believes the Food Standards Agency should issue advice now to food manufacturers to avoid using certain additives. She says that the suspect additives are often used in poor quality foods to make them appear more palatable. "Take fruit-flavoured drinks. They often contain a lot of additives aimed at mimicking natural products. A drink may contain 5 per cent fruit and manufacturers add vitamin C to market it as a healthy product, but the rest is sugar, water and additives. Not only may additives be contributing to family disharmony, but they are masking poor ingredients which deprive children of valuable nutrients."
Foods containing high levels of additives tend to be consumed by poorer families who are less able to afford higher quality, healthier alternatives. Dalmeny says: "It's easy to tell people to read the labels, but not everyone knows that these additives are suspect. How many people actually know that E102 is tartrazine (one of the suspect additives)? Understanding food labels can be quite technical and some of the additives appear in unexpected places - like tartrazine in tinned mushy peas.
So what food can be eaten that does not cause harm to consumers? Even those children who do eat a healthy balanced diet may be at risk from pesticide residues in fruit and vegetables. Sandra Bell, food and farming campaigner at Friends of the Earth explains: "There is concern about the impact of OPs (organophosphate pesticides). They are known to affect the central nervous system and scientists have suggested that behavioural problems in children could be linked to OP exposure. The most vulnerable time is for the fetus during pregnancy but young children may also be at risk."
One organophosphate, chlorpyrifos, has been banned in the US because of concerns that it may be linked to brain damage, but it is still used by European farmers. Causal links between exposure to chemicals and toxic effects for children are notoriously difficult to prove and so far the British government has been unwilling to accept that there may be a risk from long-term exposure to low levels of organophosphates.
Bell adds: "New regulations are being brought in on processed baby foods - they must not contain any pesticide residues. But unless they are buying organic food parents giving their children fresh fruit and vegetables do not have that guarantee." Some supermarkets, such as Waitrose, Marks & Spencer and Co-op, are looking to supply produce without organophosphates, and Friends of the Earth and other campaigners want to see tighter controls on the use of pesticides introduced across the European Union.
For the majority of British children, who are consuming less than half the recommended five portions of fruit and vegetables a day, concerns about pesticide residues may seem academic. It is clear, however, that it is high time we put food and diet much higher up the agenda.