Food and Behaviour Research

Donate Log In

Food Affects Behaviour: 20+ Years of FAB Research – What next? - BOOK HERE

What not to feed your child

by Andrew Purvis

10 April 2005 - The Observer

The bad mood diet of sugary drinks and E-additives

Hydrogenated and trans fats

  • May cause: Dyslexia, dyspraxia, learning difficulties, autism.
  • Where they are found: Cakes, pastries, biscuits, bread, margarine, snacks (such as popcorn), commercially fried foods - including some French fries and hamburgers.
  • What they do: Unlike the liquid omega-3 fatty acids lacking in most children's diets, these solid man-made fats have been shown in animal studies to make the brain membrane less fluid - and there is good evidence that they alter the signalling ability of neurotransmitters or chemical messengers. Some scientists believe the wrong kinds of fat in the diet may be a factor in dyslexia, dyspraxia (the inability to plan and execute actions, including communication), autism and ADHD - though few studies support this. 'Children are replacing essential fats that would make their bodies and brains work properly with ones that are clogging up the machinery,' says Dr Alex Richardson. Hydrogenated fats often contain trans fats, acknowledged by the FSA and others to raise 'bad' cholesterol and increase the risk of heart disease. In 1993, Flora reduced the hydrogenated fat content of its margarine from 21 per cent to 1 per cent (the label says 'virtually trans fat free'); others have been slow to follow.

Refined carbohydrates

  • May cause: Irritability, depression, antisocial behaviour, aggression, low IQ, reduced sense of smell and taste (affecting appreciation of healthy food).
  • Where they are found: Products made from processed white flour (white bread and pasta), cereals, crisps and snacks.
  • What they do: It isn't so much what they do as what they don't. A diet high in refined carbs is likely to be low in selenium (a deficiency linked to irritability and depression), chromium (essential for blood-sugar control), zinc, iron and B vitamins. Deficiency in the last three was implicated in a 14-year study concluded last year, examining the links between childhood diet and antisocial behaviour as teenagers. Compared to those with a healthy diet, malnourished children showed a 51 per cent rise in aggression at 17. According to Professor Adrian Raine of the University of Southern California, 'Poor nutrition characterised by zinc, iron, vitamin B and protein deficiencies leads to low IQ, which leads to later antisocial behaviour. These are all nutrients linked to brain development.' Similar conclusions were drawn from a 2002 study of young offenders at Aylesbury prison, whose diet was supplemented with vitamins and essential fatty acids. Antisocial behaviour fell by 35 per cent. In a study at the Massachussetts Institute of Technology, children who ate the most refined carbs had IQs 25 points lower than those who ate the least.

Added sugars

  • May cause: Mood swings, hyperactivity, poor concentration.
  • Where they are found: Sugary drinks, sweets, coated breakfast cereals, chocolate (in which sugar is often number two in the ingredients, after milk).
  • What they do: As a fast-acting carbohydrate, sugar is claimed by some to boost blood-sugar levels and create a surge of energy and an upbeat mood - though the sugar industry (see main story) denies any link between sugar and 'hyperactivity or any other type of "bad behaviour" or learning difficulties.' However, its 'empty calories' contribute nothing in terms of nutrition. 'If children slurp cans of surgary drinks on the way to school,' says Dr Richardson, 'it puts them on an artificial high in terms of brain function, but that stimulates the release of too much insulin which causes blood-sugar levels to plummet. In a short time, their brains are in a fog. They can't concentrate, they're irritable and find it hard to hold on to stable emotional reactions.' So far, evidence has been largely anecdotal: many parents, teachers, nutritionists and some scientists insist there is a link.

Chemical additives

  • May cause: Hyperactivity, tantrums.
  • Where they are found: Crisps, snacks, sweets and drinks, particularly those with an orange or yellow colour. About 40 per cent of products aimed at children contain chemical additives, according to the Food Commission (which lobbies for a healthier diet for children). Among those claimed to influence behaviour are sunset yellow (E110), carmazoine (E122), ponceau 4R (E124) and the preservative sodium benzoate (E211). MSG, a flavour enhancer in snacks, is another. 'Glutamate is a brain stimulant in the way it's given,' argues nutritionist Patrick Holford, 'because it enhances sensory perception by making things taste better. Some children react badly to it.'
  • The FSA, while agreeing to commission more research, says the evidence 'is inconclusive and remains an area of scientific uncertainty.'
  • What they do: Though described as 'sketchy' by the British Nutrition Foundation and others, a Southampton University study in 2002 found that a quarter of three-year-olds consuming E-additives in a drink showed signs of hyperactivity and tantrums. (The study, finally published in 2004, is described by Dr Alex Richardson as 'sound, conducted by serious researchers, as impeccably as you could do a study of that kind'.) On the Food Commission's dedicated website ( dozens of parents have since posted anecdotal evidence of behaviour changes in children who consumed E-additives. All such additives are tested for safety and approved for use in Britain.

High-GI foods

  • May cause: Mood swings, lethargy, depression.
  • Where they are found: Baguettes, bagels, pizza, instant white rice, fries, instant mashed potato.
  • What they do: Like sugar, foods at the top of the glycaemic index (which are broken down quickly and converted into glucose) create a surge of energy and an elevated mood. When insulin kicks in to deal with the sugar 'high', the opposite is felt. High-GI foods are best avoided by diabetics. The link with mood is less accepted.


  • May cause: Hyperactivity, anxiety, cravings, insomnia, tiredness.
  • Where they are found: Fizzy drinks, energy drinks, tea, coffee (caffeine).
  • What they do: Stimulants alter mood and behaviour - but the jury is out on whether the small amounts in caffeinated drinks and food affect kids. In 2003, a study of 200 teens in the US showed that those with a high caffeine intake were less mentally alert - a claim disputed by the soft drinks industry. Researchers found the average daily intake of caffeine was 63mg, equivalent to half a cup of coffee.

Copyright Guardian Newspapers Limited 2005