Food supplements may prompt enormous improvement in the educational abilities of children with learning difficulties, a study has found.

The study, examining the effect of fish and vegetable extracts on the concentration and learning levels of 120 six to 11-year-olds from 13 primary schools, is being run by Durham county council.

Researchers say it is already showing signs that food supplements bring enormous benefits for those with neuro-developmental disorders, such as dyslexia, dyspraxia, attention deficiency hyper-activity disorder and autistic spectrum disorder.

Half of the children are being given daily supplements, while the other half receive a placebo - neither group is aware of which they are taking. Each day, breathalysers measure the levels of fatty acids in the children's bodies.

Results so far have been marked. One child's reading skills have improved by the equivalent of four years after just 12 weeks of taking the supplements.

Analysis at the halfway stage of the study has shown remarkable advances among some children - believed to be taking the supplements - while others, expected to be taking the placebo, have not shown any real improvement.

Although the results will not be confirmed until the full study is completed and it is revealed which children are taking the placebo, Dr Madelaine Portwood, a senior educational psychologist at the county council, who is leading the trial, has described the findings so far as a "landmark".

She said: "The children's social skills seem to be improving because they are more confident. They are becoming more socially interactive and perhaps this increases the motivation to learn."

Dr Portwood said her 10-year-old son is taking the food supplements - which contain fish oil as a source of omega 3, evening primrose oil and vitamin A - and has shown a marked improvement.

"I wouldn't give them to him if I did not feel they did him any benefit," she said.

The study is being funded by the Dyslexia Research Trust in Oxford and the supplements are being provided by Equazen Nutraceuticals.

A spokesman for The Dyslexia Association said: "We are interested in all research which helps dyslexics. But we are keen not to raise people's expectations at a so-called "cure". We are also concerned that there should be proper research into the long-term effects and that such research is properly peer reviewed.

"We don't believe there will be a cure, or that one exists at the moment. So-called cures can help some people and not others, so that needs to be taken on board. The so-called brain foods, or supplements, are understood to show improvements in concentration, but it is teaching in the classroom which consistently works."

Results from the Durham study will be published in September.