But in Britain we eat an average of just 50 grams of fish a week, so this is an optimistic target. 'There is no scientific basis for this amount,' says Professor Jack Winkler, former director of the Nutrition Policy Unit at London Metropolitan University.
Evidence that it reduces pain and inflammation if you have arthritis is also strong. Omega-3s have been tried as a treatment for asthma, with limited success.
Results are better for macular degeneration, which damages the centre of the eye and can lead to blindness.
Last week scientists reported that women who take fish oil supplements reduce their risk of breast cancer by a third.
But while experts agree omega-3 pills can cut the risk of heart disease and are vital for brain development in the womb, opinion is divided over other benefits.
A trial of 450 school pupils by Professor Kirby found no difference in reading, spelling or handwriting between those who got fish oil for a year and those on a placebo.
Another trial failed to show that fish oil supplements helped keep elderly patients' minds sharp. The results of a review of research into the benefits of omega-3 on children with ADHD were too inconsistent to draw any conclusions.
'It relied on the mothers' opinion.' More reliable, he says, is evidence presented at the recent conference, which showed a measurable effect of fish oil on children's brains.
Robert Mc Namara, associate professor of psychiatry at the University of Cincinnati College of Medicine, gave healthy eight to ten-year-old boys a dose of either 0.4 grams or 1.2 grams of omega-3 fatty acids or a placebo every day for eight weeks.
One study of more than 3,500 patients in 2006 found those eating the most fish cut their risk of developing the disease in half.
The FSA recommends eating two portions - or 240 grams - of fish a week, one of which should be oily.
He dismisses the trial that found no effect on primary school pupils.