September 30//University of Iowa -- Fish may not be brain food after all, a new study suggests.

Older women with higher blood levels of omega-3 fatty acids did not have any better memory or thinking skills after six years than women with lower levels, says research.

Fish high in omega-3 fatty acids include salmon, tuna, swordfish, mackerel and sardines. A diet rich in fish has been touted as a way to improve brain health, but research results on its effectiveness have been mixed.

Researchers at the University of Iowa examined data on 2,157 women ages 65-80 who participated in the Women's Health Initiative research trials for hormone therapy. The women were given annual tests for their thinking and memory skills (verbal memory, verbal knowledge, verbal fluency, visual memory, spatial ability, fine motor speed and working memory) for about six years.

At the beginning of the study, they had blood tests that measured the amount of omega-3 fatty acids in their blood. It was a gauge of the fatty acids that they had consumed over the last two months. The blood tests were repeated for a subset of women one year into the trial, but not at the end.

Among the findings published in the online issue of Neurology, the medical journal of the American Academy of Neurology:

• There was no difference in thinking and memory skills between the women with high and low levels of omega-3 fatty acids in their blood at the time of the first memory tests.

• There was also no difference between the two groups in how fast their thinking and memory skills declined over six years.

• However, the women with high levels of omega-3s in their blood had slightly better fine-motor speed and verbal fluency.

"Our study is not necessarily the definitive" answer on omega-3 fatty acids, says lead author Eric Ammann of the University of Iowa in Iowa City. One limitation of the research is there was only one single measure of omega-3 fatty acids in the blood at the start of the study, he says.

A number of other observational studies have found a protective association between omega-3s and brain health, but more rigorous randomized-controlled studies generally have found no effect over short treatment periods, he says.

Senior author Jennifer Robinson, a professor of epidemiology and medicine at the University of Iowa, adds, "We really think that dietary pattern throughout your lifespan is what's important in determining heart and brain health in later life. The take-home message is people should be eating a heart-healthy and brain-healthy diet and doing physical activity throughout their lifespan. That's what's going to preserve their cognitive function as they age."

Neurologist Victor Henderson, a professor in health research and policy at Stanford University, says, "It looks like if dietary omega-3 fatty acids influence brain health, then the effect is probably not very large."