Most of us do not relish the prospect thought of losing our mental faculties as we age.
Research has been published which suggests that high levels of DHA (docosahexaenoic acid, an omega-3 fat found in certain species of fish) are associated with a substantially reduced risk of dementia and Alzheimer's disease. This sort of study cannot be used to actually prove that it is DHA that is the critical factor, but it is known that DHA makes up a significant proportion of the fat found in the nerve cell membranes in the brain. With this in mind, it's not too difficult to posit that ensuring good levels of DHA in the body might be important to brain function.
The link between fish consumption, omega-3 levels, and brain function have recently been reexamined in two studies that appear in this month's edition of the American Journal of Clinical Nutrition. In one of these studies, the relationship between fish intake and brain function (as measured by a battery of tests) was assessed in a group of more than 2,000 Norwegians aged 70-74 years. [1] The researchers found that eating an average of 10g or more of fish a day, compared to eating less fish than this, is associated with better brain function and lowers the risk of being rated with poor cognitive performance.
One thing that strengthens the idea that there is something in the fish that's doing good is the fact that there was a dose-response relationship between fish intake and brain function: In other words, the more fish that was eaten, the better the brain function. This relationship held up to an intake of 75g a day, after which there appeared to be no additional benefit.
In the second study, researchers measured blood levels of omega-3 fats in more than 800 men and women aged 50–70 and compared these to brain function (again, measured by a battery of tests) [2]. The participants in this study were assessed over a three-year period. Individuals with higher levels of omega-3 fats were found to be significantly less prone to decline in two tests of cognitive performance. However, there was no relationship found between omega-3 levels and other tests of brain function, including memory and word fluency.
The authors of this second study call for randomized controlled trials to assess the potential for omega-3 fats to preserve or enhance brain function. Such research, if properly conducted, would help settle the question once and for all whether omega-3 fats can help preserve brain function as we age.
References:
1. Nurk E, et al. Cognitive performance among the elderly and dietary fish intake: the Hordaland Health Study. American Journal of Clinical Nutrition 2007; 86(5): 1470-8.
2. Dullemeijer C, et al. n 3 Fatty acid proportions in plasma and cognitive performance in older adults. American Journal of Clinical Nutrition 2007; 86(5): 1479-85.
Dr. John Briffa is a London-based doctor and author with an interest in nutrition and natural medicine.
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