Consuming oily fish high in omega-3 fatty acids has long been endorsed for its ability to keep brains active and cut the risk of a stroke.

A new study reveals that omega-3 fatty acids may actually have no benefit at all when it comes to improving cognition. Researchers at the University of Iowa examined data on 2,157 women ages 65 to 80 who participated in the Women's Health Initiative research trials for hormone therapy. The findings are published in the journal Neurology.

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.

Blood tests were taken to measure the amount of omega-3s in the participants' blood 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 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. In addition, most randomized trials of omega-3 supplements have not found an effect," study author Eric Ammann, MS, of the University of Iowa in Iowa City, said in a news release.

"However, 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. We know that fish and nuts can be healthy alternatives to red meat and full-fat dairy products, which are high in saturated fats."

Previous studies have attributed oily fish with the ability to cut post-natal depression, reduce the risk of Altzheimer's disease and diabetes, stroke and arthritis as well as help children perform better in exams and even add two years' to a person's life expectancy.

Fish high in omega-3 fatty acids include salmon, tuna, swordfish, mackerel and sardines,