Of course, mom didn't know about omega-3 fatty acids, but the concept of fish as 'brain food' has been around for a very long time. (I first heard it 70 years ago.) Three international studies have suggested that omega-3s and fish intake protect against cognitive decline, dementia, and Alzheimer's disease.

The first study, from the Netherlands, showed that blood levels of omega-3s predicted changes in cognitive ability - measured using a battery of 5 tests - over a 3-year period. For every doubling in omega-3 levels, the subjects showed 9% - 12% less decline in cognitive ability tests.

The second study was from Norway. Those subject between 70 and 74 who ate on average 10 gm of fish a day (about1/3 of an ounce) were significantly less likely to show poor cognitive performance than those eating less than 10 gm daily. The more fish people ate (and not just fatty fish), the better they scored!

Finally, a French study spreads over 3 cities, including more than 8,000 over-65s, looked at weekly fish consumption in all cases of dementia occurring in the next 4 years. Weekly fish consumption was linked to a 35% reduced risk of Alzheimer's disease and a 40% reduction in all-cause dementia. Daily fruit and vegetable intake was linked with a 28% reduced risk of dementia, compared with lesser rates of intake.

These findings should help you make up your mind while you're waiting for the definitive study - a prospective comparison of groups of people eating a lot or a little fish (decided in random fashion) over a long enough period to assess the effect on the occurrence of dementia. It will take, probably, 2 years to plan such a study, 2 years to start it, and 4 years for a follow-up, leading to another 1-2 years' analysis. By that time it may be too late for many of us. Let's just rely on what mom told us.