A meta-analysis finds that taking omega-3 supplements may not do much to preserve memory, but here's why the finding isn't the last word.

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Despite the widely touted benefits of omega-3 fatty acids for preserving cognitive function and memory, a new review by the Cochrane Library finds that those effects may be overstated: healthy elderly people taking omega-3 supplements did no better on tests of thinking and verbal skills than those taking placebo.

A number of previous studies have associated omega-3 consumption with better brain health and a lower risk of Alzheimer’s disease. One recent study by Columbia University researchers found that people who ate diets higher in omega-3s had lower blood levels of beta amyloid, the telltale protein that gums up brains in Alzheimer’s patients. In another study published in the journal Neurology in February, researchers showed that people with the highest levels of omega-3s in their blood had bigger brain volumes and performed better on tests of visual memory and abstract reasoning, compared with those with the lowest levels.

Much of this previous data has been observational, however. So, for the Cochrane review, researchers looked specifically at so-called “gold standard” studies, those that randomly assigned people to take either omega-3s or a placebo and then tracked the participants over time. The authors of the review, from the London School of Hygiene & Tropical Medicine, included three studies involving a total of 3,536 people over the age of 60, which lasted between six and 40 months. All the participants started the studies in good cognitive health.

(MORE: Omega-3s May Guard Against Brain Decline)

In two studies, researchers compared the effects of omega-3 (fish oil) capsules versus placebo capsules containing olive or sunflower oil. In the third study, participants used either omega-3-fortified margarine or a regular margarine spread. In the end, the data showed that participants who got extra omega-3s performed no better on standard tests of mental abilities, memory or verbal fluency than those who took placebos.