The omega-3 polyunsaturated fatty acids plentiful in fish oil have been building a powerhouse reputation for keeping the heart and circulatory system healthy and an increasingly solid record of aiding in a number of psychiatric conditions and preserving brain function.
But a rigorously designed study comparing septuagenarians taking fish oil supplements for two years with those on a placebo has found that for the mentally fit elderly, adding fish oil to the diet did not preserve or enhance mental function.
The study's findings seemed to surprise even the researchers from London's School of Hygiene and Tropical Medicine who conducted it. Dr. Alan Dangour, the lead author, suggested that for individuals in their 70s, disease processes that, in some, will go on to erode memory and cognitive function may already be well underway, even if not yet evident. While the study is the longest and largest of its kind to date, Dangour said, it may not have been long enough for any "true beneficial effects to be detected" among cognitively healthy older people.
The study was published Wednesday in the American Journal of Clinical Nutrition.
Some 867 subjects between ages 70 and 80 participated in the study in England and Wales. Half the subjects got a daily tablet of 700 mg of fish oil (200 mg of eicosepentaenoic acid, or EPA, and 500 of docosahehexaenoic acid or DHA), while half took an olive oil placebo. The study found that supplementation with fish oil did increase levels of polyunsaturated fatty acids in the seniors' blood. But those on fish oil tablets had no better cognitive function, and no lower rates of mild cognitive impairment, than those who were not.
A 2006 study had suggested that fish oil supplementation had positive effects in Alzheimer's patients who were still mostly functioning well, although its overall effects in preventing cognitive decline in Alzheimer's disease were not positive. Other trials of fish oil and memory preservation have had mixed results.
For a good overview of the research on fish oil and health, check this out.