Omega-3 fatty acid supplements do not decrease the chances of declining mental abilities in older adults, says a new review of studies done on the subject.

"The evidence suggests, from what is available at the moment, that taking supplements rich in omega-3 fatty acids is not going to benefit cognitive health later in life," said Alan Dangour, a nutrition researcher from the London School of Hygiene & Tropical Medicine, who worked on the new study review.

Researchers gathered evidence from high-quality studies done on omega-3 supplements and their effects on mental abilities. Nearly 3,600 people had taken part in the trails that lasted anywhere between 4 months and 3 years. All participants were above age 60 and none had any memory or cognitive decline at the start of the trial.

They found that people who took omega-3 capsules didn't do better at cognitive tests compared to people who were on placebo.

Previous research said that omega-3 fatty acids provide some benefits with regard to cognitive decline.

"From these studies, there doesn't appear to be any benefit for cognitive health for older people of taking omega-3 supplements. However, these were relatively short-term studies, so we saw very little deterioration in cognitive function in either the intervention groups or the control groups. It may take much longer to see any effect of these supplements," said Alan Dangour, a nutritionist at LSHTM and co-author of the review report.

Researchers say that fish oil capsules might be as effective as people think they are, but eating fish is still recommended as it offers numerous benefits.

"Fish is an important part of a healthy diet and we would still support the recommendation to eat two portions a week, including one portion of oily fish," said Dangour.

"The truth is many people are spending a lot of money on supplements without solid evidence they do something," Dr. Nikolaos Scarmeas, neurology and aging researcher at Columbia University Medical Center in New York told Reuters Health. Scarmeas was not involved in the present study.