Oily fish such as salmon is a source of omega-3
The head of a study into whether omega-3 supplements improve "mainstream" children's learning and behaviour says more research is needed to determine their effectiveness.
Prof Amanda Kirby's team undertook a 16-week study with 450 young children at the University of Wales, Newport.
It suggested children's reading, spelling and co-ordination were largely unaffected by taking supplements.
However, teachers reported improvements in the children's attention in class.
Prof Kirby is medical director of the university's Dyscovery Centre, which helps people with developmental disorders.
She said little omega-3 research had been carried out using a "normal, mainstream school population".
Claims have been made how omega-3 can boost brain power, keep hearts healthy, strengthen bones and more, but Prof Kirby said little was really known about the effects of these fatty acids.
"I got interested in this field because of my interest in developmental disorders. I looked at all the work and thought that it had started with children with disorders rather than with ordinary children," she said.
"What I've learned is that we know so little about fatty acids."
Omega-3 is the name given to a family of unsaturated fatty acids found mainly in oily fish and also in eggs, meat, milk and cheese.
The study, published in the journal Research in Developmental Disorders, involved 450 children aged eight to 10 years old, across a range of social classes at 17 schools in Newport, south Wales.
Over four months, half the children were given supplements while half were given placebos - with children, parents, teachers and scientists all unaware of who had taken what.
Reading and spelling
Prof Kirby said a range of measures were used to determine the effectiveness of the supplements on the children.
"Psychological assessments [were done], teacher reporting of behaviour, parent reporting of behaviour, and fatty acid levels were taken, all before and after [the supplements]," she said.
"What we found is that things like reading and spelling and co-ordination didn't really improve.
"We did find that teacher scores on attention did improve in the active group."
The children's levels of "cheek cell" fatty acids were measured before the research, which Prof Kirby said was important because it was not known what "normal" levels were.
She found that during the course of the research, the good fatty acid levels of the children receiving supplements continued to rise but the levels of omega-6 nearly all fell.
"We wouldn't expect to see dramatic changes [in behaviour and learning] because the children didn't have a disorder," said Prof Kirby.
"The fact we saw some some changes in the behaviour and learning of the children is significant and we need to understand more.
"The fact we can alter [fatty acid] levels with supplements is also significant."