You don't need a science degree to make a connection between food and behaviour. Every mother witnesses it first hand at birthday parties or later when her child's laughter quickly gives way to demands and whingeing, tears and ultimately screams that generally subside after a bath and some real food.

But for some children there is no "coming down". You may have noticed there are often one or two kids at those parties who spin out more than the rest - they disrupt the games, can't wait for their turn and are easily upset or aggressive. They're displaying the symptoms of Attention Deficit Hyperactivity Disorder (ADHD), currently affecting between 3 and 10 per cent of the population, predominantly young children.

"You can pick them out in the surgery," Dr Robyn Cosford says about children with ADHD. "They climb all over the furniture, they try to pull things off your desk, they can't sit still - they're literally in your face the whole time."

ADD (Attention Deficit Syndrome) and ADHD are part of a spectrum of diseases including autism and Downs Syndrome that Dr Cosford is studying. ADD (Attention Deficit Disorder) is an inattention that tends toward dreamy-ness.

"These are kids who disappear into space," says Dr Cosford. "In addition to inattentiveness, children with ADHD are restless and unfocussed and have to be moving the whole time."

Although Dr Cosford has been compiling research over the last three years, as a mother of five, she recognised the association between diet and behaviour long before she had the chance to start studying it.

But the most significant trigger for her research came with the shock arrival to her surgery of a mother and the carer of a 28 year-old young man with the dual diagnosis of Downs Syndrome and autism.

"I don't know what you've done," said the mother. One year earlier Dr Cosford had met the young man and his mother and suggested correcting his diet and giving him baseline nutrients to help his behaviour.

"I looked at them sitting in front of me and I thought, " Uh Oh, what have I done?" says Dr Cosford. "When he first came to me he had extreme behaviour - he was irritated, aggressive, violent, he only spoke one or two words and had marked rituals like head banging and rocking. He wouldn't sleep till 3 or 4am every morning and he was on multiple medications that weren't making the slightest difference."

During the year the mother had adhered strictly to the prescribed diet. Her son's behaviour had settled, he had stopped all the rituals and he was sleeping at normal times. But the biggest surprise to everyone including Dr Cosford, was that he had started spontaneously speaking - he had progressed from a few words up to whole sentences.

"That really challenged all the medical paradigms," she says, "the belief that conditions like Downs Syndrome and autism are fixed and you cannot alter mental function. That incident encouraged me to start searching the literature and studying it much more closely. And the work has just gone on from there."

According to Dr Cosford there are correlates between certain foods and the onset of childhood diseases. "There is a direct connection between the early introduction of cows milk and development of recurrent ear infections and a further correlation between recurrent ear infections and ADHD."

Currently children with symptoms of ADHD are routinely prescribed an amphetamine known as Ritilin. This stimulant increases the dopomine levels in the part of the brain responsible for attentiveness and has the effect of calming kids with ADHD and improving their concentration levels.

The down side is that it's a drug of addiction. According to Dr Cosford it does give symptomatic improvement but usually at the expense of appetite and sleep disturbance. Its effects are known to wear off over time and there is mounting evidence indicating that amphetamines do cause brain damage.

Despite the surrounding uncertainties, Ritilin prescription has risen 150 percent since 1995. In Australia over 50,000 kids with ADHD are using prescription drugs to cope with their symptoms, with the greatest growth in use in WA. In certain school districts in the United States, where Ritilin is positively encouraged by educators, its use has soared to 40 per cent of all school age kids.

And why haven't the parents tried changing their kid's diets before giving them drugs? "Difficult children make mothers desperate," says Sue Dengate in Fed-Up (Random House Aust. 1998). It is so much easier pushing junk food into screaming young mouths than broccoli.

Even our Health Minister Michael Wooldridge agrees, "I think many parents are utterly exasperated, I've been like that myself once or twice," he said in a statement reported by Simon Kearney in the Daily Telegraph.

But if you are looking for alternatives to a legacy of drug use in an under 10 year-old, getting back to a basic, "you are what you eat", approach may not be the easy option but it could prove more intelligent and long-lasting.

Every human being is different and reacts to substances uniquely but there are guidelines for avoiding danger areas. The five most common food allergens are: milk, wheat, corn, chocolate and citrus.

Dr Cosford recommends a diet free of artificial colours, flavours, sugar and additives. "A wholefood diet, like those from a couple of generations ago before the introduction of chemicals and processing.

"Most children need to be diary-free and require between five and nine serves of fruit and veggies a day," she says. It can be a matter of trial, error and observation until you can pinpoint a dietary irritant to your child's behaviour.

But when you find it, remember in most cases: If you don't buy it, they won't eat it.