Studies in Norway, the Netherlands and New Zealand found that older people who ate fish regularly had better cognitive function, scoring better on six tests, including those for memory, visual conception, attention and verbal fluency.

The results, published in the American Journal of Clinical Nutrition, also found that the more fish people ate, up to a limit of about 80g a day, the greater the effect.

However, the Norwegian study of more than 2000 men and women aged 70-74 had an added finding, which questioned how much of the brain-boosting effect was due to omega-3s, which have long been considered good for the brain and are found in greatest amounts in fatty fish such as mackerel, salmon, trout and herring.

The researchers found that people who ate leaner fish such as barramundi and perch, which in turn had lower amounts of omega-3s, gained just as much benefit as those who had the fattier fish.

They said this suggested the effects could be due to one or more other compounds in fish and not just the omega-3s.

The study also found that people who were given supplements such as cod-liver and other fish oils did not perform as well in all the cognitive tests as those who ate fresh, frozen or canned fish.

From the December 3, 2007, Prepared Foods e-Flash