Omega 3 fatty acid for the prevention of cognitive decline and dementia
Dementia is progressive and debilitating, manifesting in symptoms such as loss of memory, language problems, and difficulties in performing activities of daily living. Global estimates suggest that by the year 2040 more than 80 million people will be affected with dementia worldwide.
Pharmacological therapies appear to produce small cognitive improvements for some patients, but currently appear unable to halt dementia’s progression. There is significant interest in identifying modifiable risk factors, such as lifestyle, that may prevent dementia, particularly dietary interventions such as omega-3 fatty acids.
Omega-3 fatty acids are responsible for many important jobs in the human body. We get these fats through our daily diets; the three major omega-3 fats are: alpha linolenic acid (ALA), from sources such as nuts and seeds; as well as eicosapentoic acid (EPA) and docosahexaenoic acid (DHA), from sources including oily fish such as salmon and mackerel. An increasing body of scientific literature has investigated the link between omega-3 dietary consumption and measures of cognitive function; a number have hinted that omega-3 fatty acids, and DHA in particular, may be involved in keeping nerve cells in the brain healthy into old age. Cochrane researchers, working with the Cochrane Dementia and Cognitive Improvement Review Group, first investigated this question back in 2006, and have recently updated the Cochrane Review with the newest evidence focusing on this question.
The Cochrane team, led by Emma Sydenham at the London School of Hygiene & Tropical Medicine (LSHTM, UK), examined evidence from three high-quality trials comparing the effects of omega-3 fatty acids taken in capsules or margarine spread to those of sunflower oil, olive oil or regular margarine. A total of 3536 people over the age of 60 took part in the trials, which lasted between six and 40 months. None of the participants had any signs of poor cognitive health or dementia at the start of the trials. 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.
“From these studies, there doesn’t appear to be any benefit for cognitive health for older people of taking omega-3 supplements,” said Alan Dangour, a nutritionist at LSHTM and co-author of the report. “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.”
The researchers conclude that the longer term effects of omega-3 fatty acids on cognitive decline and dementia need to be explored further, particularly in people with low dietary intake. In the meantime, they stress other potential health 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.
Sydenham E, Dangour AD, Lim WS. Omega 3 fatty acid for the prevention of cognitive decline and dementia. Cochrane Database of Systematic Reviews 2012, Issue 6. Art. No.: CD005379. DOI: 10.1002/14651858.CD005379.pub3.