A new placebo-controlled trial has reported that daily supplements of omega-3 and omega-6 fatty acids could slow mental decline in elderly people, adding to a growing body of evidence linking the fatty acid to better cognitive function.
Indeed, only recently scientists from the Karolinska University Hospital Huddinge in Sweden reported that omega-3 fatty acid supplementation, mainly DHA (docosahexaenoic acid), may slow mental decline in people with very mild Alzheimer's disease (Archives of Neurology, Vol. 63, pp. 1402-1408).
Growing body of science
The new research, published in the October issue of the journal Neuroscience Research (Vol. 56, pp. 159-164), adds to the growing body of science that have linked regular intake of omega-3s to improved cognitive function, behaviour and learning.
Moreover, brain concentrations of the omega-6 fatty acid, arachidonic acid (ARA), are also said to decrease naturally with ageing, so supplementation may boost neuronal membrane levels.
“There were some reports suggesting the effect of omega-3 fatty acids such as EPA and DHA on cognitive functions in human subjects, but very few reports have focused on the effect of omega-6 fatty acids,” wrote lead author Susumu Kotani from the Japan Foundation for Aging and Health. “The present pilot study of ARA and DHA supplementation showed remarkable memory improvements in the human patients with organic brain lesion or mild cognitive impairment.”
How the study was done
The Japanese scientists recruited 21 patients with mild cognitive impairment (9 females, average age 68) and randomly assigned them to receive DHA plus ARA supplements (six capsules containing 40mg/capsule ARA, DHA, and 0,16mg/capsule of asthaxanthin, Suntory Ltd., Japan) or six placebo capsules per day (40mg/capsule of olive oil).
Ten of the participants had been diagnosed with so-called organic brain lesions (haemorrhage or traumatic brain injuries), and eight had been diagnosed with early Alzheimer's disease (AD).
The mental function of the subjects was assessed at the start of the trial and then again after 90 days of supplementation, using the Japanese version of repeatable battery for assessment of neuropsychological status (RBANS).
Kotani and co-workers report that ARA plus DHA supplementation produced significant improvements in the immediate memory and attention RBANS scores (eight and five points, respectively). No effect on delayed memory was observed.
Effect on memory scores
For the subjects with organic brain lesions taking the supplements were found to have the greatest improvements in immediate memory scores (10 points), while delayed memory scores were found to increase by 14 points for this subset.
No improvements were observed for the placebo groups or for the people with early Alzheimer’s disease who took the supplements.
“It is suggested from these data that ARA and DHA supplementation can improve the cognitive dysfunction due to organic brain damages or ageing,” said Kotani.
The mechanism behind the supplement's effect on cognitive function seems to be specific to the type of omega oil, said the researchers.
“DHA might be directly involved in improvements not of the synaptic plasticity and cognitive function, but of the membrane function and regional cerebral blood flow,” they wrote.
Improved membrane fluidity
Previous studies have proposed that DHA is involved in the membrane of ion channels in the brain, making it easier for them to change shape and transit electrical signals.
“It is likely that the improvement of cognitive functions after the ARA supplementation might be due to the improved membrane fluidity that can affect neurogenesis and/or synaptogenesis,” said the researchers.
More research is needed to investigate further the relationship between omega-3 and omega-6 intake and cognitive function, particularly in elderly people with healthy cognitive function and other populations.
The study was financially supported by the Japan Foundation for Ageing and Health, the Narishige Neuroscience Research Foundation, and the Japan Ministry of Education, Science and Technology. - (Decision News Media, November 2006)
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