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Study shows no effect of omega-3 fatty acids on brain function

April 28, 2010

Supplements of omega-3 fatty acids may not improve brain function in the elderly, a new UK study indicates.

In the randomized controlled trial, 748 participants aged between 70 and 79 with healthy cognitive function were randomly assigned to receive capsules containing olive oil (placebo) or fish oil capsules containing 200 mg eicosapentaenoic acid (EPA) and 500 mg of docosahexaenoic acid (DHA) (1). After two years at the end of the study, the group that received the omega-3 capsules had higher blood levels of EPA and DHA, compared with the placebo group. However, cognitive function, measured using a verbal learning test, did not change in either the omega-3 or placebo groups. In addition to no cognitive enhancement in the omega-3 group, no cognitive decline was observed in the group, which received olive oil.

Experts criticized the study results because they do not indicate that there are no cognitive benefits associated with fish oil supplementation in this or any other population. Actually the trial did not compare the effects of EPA and DHA in fish oil with a real placebo, but with arachidonic acid in olive oil, which also has a structural role in the brain. Moreover, the measurement of essential fatty acids was only done in the blood plasma (instead of red blood cells), which mainly reflected the participants’ recent eating habits. Furthermore, the study participants were cognitively healthy, so the expectation was not of improved cognition, rather attenuation of cognitive decline. Given that cognitive function did not change from baseline in either the fish oil or olive oil groups suggests that the duration of intervention was too short.

The study challenges previous findings from other studies reporting that daily DHA supplements may improve both memory function and heart health in healthy older adults.

References

  1. Dangour A.D. et al. Effect of 2-y n-3 long-chain polyunsaturated fatty acid supplementation on cognitive function in older people: a randomized, double-blind, controlled trial. American Journal of Clinical Nutrition. 2010.