The body cannot make them itself, so must take them in through food or as supplements.
Omega-3 is found naturally in oily fish, such as tuna, salmon and sardines, as well as walnuts, pumpkin seeds, hemp seeds and oil, and flax seeds.
The Fleetwood study used Haliborange supplements costing pound;3.99 for 30 capsules. Others are available.
The benefits of omega-3, however, are the subject of much debate. Research reported earlier this year from County Durham suggests that a diet rich in omega-3 can boost the reading, memory and concentration levels of children with dyspraxia, particularly those with behaviour problems or attention deficit hyperactivity disorder (ADHD).
Omega-3 is also thought to help reduce the risk of heart disease, strokes and some cancers.
But recent research by the University of East Anglia found no clear evidence it is of any benefit. The study did not cover brain function.