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Omega-3 dementia benefits questioned by new Cochrane review

By Nathan Gray , 13-Jun-2012
Last updated on 13-Jun-2012 at 16:36 GMT

Omega-3 dementia benefits questioned by new Cochrane review

Omega-3 supplements are unlikely to prevent cognitive declines and dementia in the elderly, according to a review of the evidence published by the Cochrane Collaboration.

The systematic review assesses data from more than 3,500 elderly people, concluding that those who consume omega-3 fish oil supplements are probably not reducing their chances of losing cognitive function. The researchers, led by Emma Sydenham from the London School of Hygiene & Tropical Medicine (LSHTM), UK, said that based on the current available evidence supplements offered no benefits for cognitive health over placebo capsules or margarines, but that longer term effects are worth investigating.

“From these studies, there doesn’t appear to be any benefit for cognitive health for older people of taking omega-3 supplements,” said study co-author Alan Dangour, also of LSHTM. “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,” he said.

Reaction

Dr Marie Janson of Alzheimer’s Research UK echoed such sentiment, stating that Cochrane reviews are an ‘excellent’ way of pulling together high quality scientific evidence, but noting that the data assessed by the review only concerned relatively short follow-up periods.

“There may be longer-term benefits, but further research would be needed to investigate this,” she said.

Janson added that omega-3s should be seen as important for maintaining good health – even if the data is lacking to show any possible benefits for cognitive functions.

“We know that what is good for the heart can be good for the head so maintaining a healthy weight, eating a balanced diet, exercising and keeping our blood pressure in check are all ways that we could reduce our risk of cognitive decline and dementia later in life,” she said.

Also commenting on the review, Dr Carrie Ruxton from the Health Supplements Information Service said it is ‘crucial’ to point out that omega-3 fatty acids are vital for normal development and long-term health.

“Omega-3s are required across the whole lifecycle, beginning in the womb and continuing through to old age. They are essential for all the cells in the body, particularly those in the brain, retina, nervous system, immune function, and circulation.”

Ruxton added that although the review was set up to assess the effects of omega-3 PUFA supplementation for the prevention of dementia, none of the three trials included studies examined the effect of omega-3 PUFA on incident dementia.

Omega-3 for brains

Several studies have suggested that omega-3 fatty acids are essential for keeping nerve cells in the brain healthy, whilst others have found people who regularly consume fish that are rich in omega-3 have a lower risk of developing memory loss or Alzheimer’s disease.

However, there have been few high quality clinical trials to back up these general observations.

Study details

Together the three clinical trials reviewed followed 3536 healthy adults over the age of 60 for up to three and a half years.

The studies gathered together evidence comparing the effects of omega-3 fatty acids taken in capsules or margarine spread to those of sunflower oil, olive oil or regular margarine.

None of the studies measured whether these volunteers went onto develop dementia, but volunteers were given memory and thinking tests to monitor any cognitive decline.

The researchers found no benefit of taking the omega-3 capsules or spread over placebo capsules or spread. Participants given omega-3 did not score better in standard mental state examinations or in memory and verbal fluency tests than those given placebo. 
The team concluded that the longer term effects of omega-3 fatty acids on cognitive decline and dementia need to be explored in further studies, particularly in people with low intakes of omega-3 fatty acids in their diet.

Source: Cochrane Database of Systematic Reviews
Published online ahead of print, doi: 10.1002/14651858.CD005379.pub3
“Omega 3 fatty acid for the prevention of cognitive decline and dementia”
Authors: E. Sydenham, A.D Dangour, W.S. Lim

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