There has been talk for years that certain "brain foods" might help fend off dementia. Nuts and fatty fish containing omega-3 fatty acids are two of these supposed "brain foods."
But a recent study found that omega-3 fatty acids appeared to have no effect on women's cognitive abilities as they age.
Omega-3 fatty acids are found in a variety of foods, including nuts and fatty fish such as salmon.
The researchers measured two different omega-3 fatty acids in women over several years and found no differences in their skills or cognitive decline.
The omega-3 fatty acids levels did not appear to harm women, but they did not benefit them in cognitive health either.
This study, led by Eric M. Ammann, MS, of the Department of Epidemiology at the University of Iowa College of Medicine, aimed to find out if higher levels of omega-3 fatty acids were beneficial to older women's cognitive health.
The researchers studied 2,157 women, aged 65 and older, who were followed for an average of six years.
The women had normal cognitive skills at the start of the study and then were tested once a year throughout the study in seven areas of cognitive ability.
These areas included fine motor speed, verbal memory, visual memory, spatial ability, verbal knowledge, verbal fluency and working memory.
The researchers also measured the levels of two types of omega-3 fatty acids in the women's blood over the course of the study.
These fatty acids were red blood cell docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA).
The researchers then compared the women's levels of these fatty acids to any changes in their cognitive skills, adjusting their analyses to account for other factors that might influence cognitive abilities.
Those other factors included the women's demographics (age, race/ethnicity, income), whether they were taking hormone replacement therapy, their health history and behavior and measurements of their body, including height and weight.
The researchers found that there were no significant differences among the women in cognitive ability that corresponded to their DHA and EPA blood levels.
At both the start of the study and during follow-up, women in the highest fifth or lowest fifth for DHA or EPA levels showed no pattern of differences for cognitive ability.
The researchers therefore concluded that higher levels of omega-3 fatty acids did not appear to affect cognitive decline in older women who did not have dementia.
"In this study, higher or lower omega-3 levels had no correlation with greater or lesser cognitive abilities, in contrast to previous research showing that omega-3 fatty acids are neuroprotective in animal studies," Deborah Gordon, MD, a nutrition and preventive medicine expert who was not associated with this study, told dailyRx News.
"In general, results in humans have been inconsistent regarding potential neuroprotective effects, so this study is not alarming nor the first of its kind," Dr. Gordon said.
"In my practice, I emphasize the importance of the ratio between omega-3 and omega-6 consumption," she said. "Over the last century our omega-6 to omega-3 ration has increased dramatically, particularly in the last two decades."
"The ratio between the two oils is important because omega-3's are considered protective against the harmful effects (inflammatory, oxidizing) of omega-6's," Dr. Gordon explained. "The more omega-6 fatty acids consumed, the more omega-3's are needed and the less benefit from a given amount of omega-3's."
"I would like to see a cognitive abilities study that included consumption or levels of both essential fatty acids," she said. "I will continue to advise my patients to eat fatty fish rich in omega-3's and to limit consumption of omega-6 fatty acids, found predominantly in vegetable oils, commercially prepared foods, and some nuts."
The study was published September 25 in the journal Neurology. The research was funded by the National Heart, Lung and Blood Institute and the US Department of Health and Human Services.
One author is an employee at OmegaQuant Analytics, LLC, which offers RBC fatty acid testing. Another author is the owner of OmegaQuant Analytics and an employee of Health Diagnostic Laboratory, Inc.
Another author has received research grants from Amarin, Amgen, Daiichi-Sankyo, Genentech/Hoffman-La Roche and GlaxoSmithKline. The other five authors declared no conflicts of interest.