While a wealth of research has suggested that long chain omega-3 fatty acids may help to boost memory and could even play a role in the prevention of dementia by reducing declines in cognitive funcitoning, a new review of clinical trials has suggested that increasing levels of omega-3 are not associated with protection against age-associated cognitive declines.
"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," explained study author Eric Ammann from the University of Iowa, USA. "In addition, most randomised trials of omega-3 supplements have not found an effect."
Writing in the journal Neurology, the research team tested whether higher blood levels of omega-3 - measured by levels of red blood cell (RBC) docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) - were associated with a protection of cognitive functions in more than 2,000 women.
Despite the strong evidence from other clinical studies that such a link exists, Ammann and his team found there to be no association between RBC levels of DHA and EPA and age-associated cognitive decline in their particular study group of dementia-free postmenopausal women.
Commenting on the research, Harry Rice V.P., regulatory & scientific affairs for the Global Organization for EPA and DHA Omega-3s (GOED), noted: "Many of the popular press articles I'm reading about this study are reporting that omega-3s don't protect against cognitive decline ... What the authors concluded was that higher (vs lower) levels of red blood cell EPA+DHA were not associated with the rate of cognitive change in post-menopausal women."
"This is a far cry from a cause and effect relationship," stated Rice.
"Unfortunately, consumers are being led to believe that increased fatty fish and EPA+DHA supplement intake provide no benefit against cognitive decline," he warned. "This is irresponsible given the risk that people may base their intake decisions on such misreporting."
Indeed, Ammann added that the results of the study should not be taken out of context: "We do not recommend that people change their diet based on these results. Researchers continue to study the relationship between omega-3s and the health of the heart, blood vessels, and brain," he commented.
" It's important for consumers to keep in mind that there are a multitude of reasons (i.e. cardiovascular) to increase EPA+DHA intake via fatty fish or supplement consumption," added Rice.
The study involved 2,157 women age 65 to 80 who were enrolled in the Women's Health Initiative clinical trials of hormone therapy - in which the women were given annual tests of thinking and memory skills for an average of six years. Blood tests were taken to measure the amount of omega-3s in the participants' blood before the start of the study.
The reported 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. In addition, they reported that there was also no difference between the two groups in how fast their thinking skills declined over time.
However, the team noted that marginally significant cross- sectional differences in the results did suggest that groups with high levels of DHA and EPA fared better than those with lower levels on measures of fine motor speed and verbal fluency.
"Despite suggestive findings from some observational studies of a protective association between omega-3s and improved cognitive aging, results from randomized controlled trials of omega-3 supplements have generally not been supportive of a protective effect in cognitively intact older adults over short treatment periods," concluded the authors.
"This is consistent with our finding of no association between RBC DHA 1 EPA content and cognitive change over a median follow- up of 5.9 years."
Published online ahead of print, doi: 10.1212/WNL.0b013e3182a9584c
"Omega-3 fatty acids and domain-specific cognitive aging"
Authors: Eric M. Ammann, James V. Pottala, William S. Harris, et al