Omega-3s don't prevent cognitive decline

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If you’ve been munching down walnuts and scarfing up fish to fortify your brain against cognitive decline, you may be fueling up on omegas for naught. 

A new study runs contrary to current wisdom that omega-3 fatty acids are good for your brain. The study, published online in the journal Neurology, found that in older women, having a high intake of omega-3s did not forestall cognitive decline.

"There has been a lot of interest in omega-3s as a way to prevent or delay cognitive decline, but unfortunately our study did not find a protective effect in older women,” said study author Eric Ammann, of the University of Iowa in Iowa City.

That actually seems to fit in with the existing research. Though observational studies have found that omega-3s may be protective against cognitive decline, Ammann noted that “generally speaking, randomized controlled trials of omega-3 supplements have not found an effect on cognitive function.”

In the current study, 2,157 women between the ages of 65 to 80 were given annual tests of thinking and memory skills for an average of six years. Blood tests were taken to measure omega-3 intake before the start of the study. The researchers found no difference between the women with high and low levels of omega-3s in the blood at the time of the first memory tests. There was also no difference between the two groups in how fast their thinking skills declined over time.

Looking for explanations for the lack of effect, Ammann suggested that omega-3s may have an effect, but not in this group of older women over a relatively short period of time (six to eight years).  People’s diets can change over time, and it is not known if these women had a lifetime of high omega-3s, because this study was just a snapshot of their intake. In addition, this was a very healthy group of women at low risk of stroke and dementia. The results could be different in higher risk groups.

“It is possible that the cognitive benefits of omega-3 fatty acids are small and cumulative over a lifetime, which could explain why the trials have failed to find an effect,” he said.

He warns not to stop eating fish and nuts, because they are certainly a healthy alternative to red meat and high-fat dairy products.