A good diet could improve behaviour and learning in disruptive children, according to scientists at Oxford University.

Gordon Smith, who gives his two-year-old son only milk and juice to drink since being warned about E numbers and additives at a dad's group

Research by Dr Alexandra Richardson and her team at the department of physiology showed that essential fatty acids, found in fish and nuts, can improve brain power, increasing children's ability to learn and enhancing their behaviour.

They believe processed food not only prevents the body from working properly, but stops vitamins and minerals from nutritious food being used effectively by the body.

They claim under-achieving children with attention deficit disorder, who are currently treated with medication, could be better off with a simple change of diet.

Dr Richardson said: "What we've shown is that you can improve behaviour and learning with these oils.

"Food affects behaviour. To ignore the role of nutrition is indefensible. If you paid attention to diet you could really make a difference."

The study involved 117 children with physical coordination problems, like dyspraxia - which is thought to affect about five per cent of British youngsters.

For three months, half were given daily supplements of Omega-3 fatty acids, often known as "brain food" due to the role they play in brain development, which are found in oily fish and nuts. The rest were given dummy capsules full of olive oil.

Improvements were seen in about 40 per cent of those on omega-3, who made up to 10 month's progress in reading during the research.

Half showed such good development that they were no longer classed as having problems. When the children swapped supplements, there was a similar improvement in those who transferred to Omega-3.

Professor Jaya Henry, professor of nutrition at Oxford Brookes University, said: "I think there is little doubt that this Omega-3 is in short supply in our children's diet.

"This study is important.

"However, I do have a slight worry that if you cite certain nutrients as beneficial then you may miss the bigger picture which is about eating a good, healthy diet.

"Let's enjoy food in a way that allows us to connect with nature, which translates as eating fresh fruit, fresh veg and fresh meat.

"Children should be allowed treats, but I'm not for one minute saying that you should allow them to eat junk food ad infinitum."