Fish oil capsules are powerless to slow mental and physical decline in Alzheimer’s disease, a major clinical study suggests.
Previous research had linked fish oil - and the omega 3 fatty acid nutrients it contains - with a protective effect against the memory-destroying condition.
However no large scale clinical studies had been performed until now. The results will come as a disappointment to the UK’s 820,000 Alzheimer’s sufferers and their families, not to mention the dietary supplements industry which makes 20 per cent of its estimated £1billion UK revenue from fish oil capsules.
In the study, published in The Journal of the American Medical Association(JAMA), 402 people with mild to moderate Alzheimer’s were randomly assigned to one of two groups. One group was treated with a supplement containing DHA – an omega 3 fatty acid previously shown to have beneficial effects in animal studies – while the other group were given placebo pills identical in appearance to the fish oil capsules, but without any active substance.
After two years the two groups performed similarly in tests assessing their memory and overall health. Scans showed that the brain shrinkage typical of Alzheimer’s also occurred equally in both sets of patients.
The health supplements industry was quick to respond. The industry-funded Health Supplements Information Service (HSIS) published a statement by Dr Carrie Ruxton in which the nutritionist and communications consultant first listed a litany of “health benefits” attributed to fish oil before citing studies reporting positive results from fish oil treatment.
Ruxton referenced one study in particular, published in Alzheimer’s and Dementia in May this year. Here, researchers noted a minimal beneficial effect of DHA in patients suffering “cognitive decline” - a condition which may prefigure Alzheimer’s. However, even in this study key indicators of mental and physical health were unaffected by DHA treatment.
Five of the eight authors of the Alzheimer’s and Dementia paper were listed as employees of Martek Biosciences, an American nutritional supplements concern. HSIS’ American counterpart, the Council for Responsible Nutrition, have recently re-issued the press release accompanying that earlier, more encouraging paper.
Returning to the JAMA study, Dr Joseph Quinn, who led the work, admitted that his team “didn’t get the result [they] really were hoping for” but pointed out that the health of the patients included had already declined to the level necessary for an Alzheimer’s diagnosis. “It remains possible that an intervention with DHA might be more effective if initiated earlier in the course of the disease,” he said.
Much research has shown that people with a diet high in fish oil are less likely to develop Alzheimer’s disease yet the reasons for this remain elusive. It may be that only lifelong consumption of the oil provides the much mooted protective effect.
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