Boosting levels of docosahexaenoic acid (DHA) in the blood and eating about three fish meals each week can almost halve the risk of Alzheimer's disease in elderly men and women, reported researchers in the US last week, confirming previous results showing the benefit of fish oils on mental health.
Researchers at Tufts University in Boston measured the fatty acid levels in blood samples obtained from 1137 men and women, with an average age of 75, who were part of the Framingham Heart Study. The subjects' diets were assessed by questionnaire and those free of dementia were followed for a mean of 10 years. During the study they were assessed for the onset of new dementia including Alzheimer's Disease.
Participants who had diets rich in DHA, an omega-3 fatty acid, reduced their risk of developing dementia considerably compared with those whose diets contained low amounts of DHA, said the researchers at the American Heart Association's scientific sessions.
"Our data indicate that increased plasma phospholipid docosahexaenoic acid along with about three fish meals per week is assocated with a significant 48 per cent reduction in risk of dementia in elderly men and women. A high level of plasma PC linoleic acid due to an increased intake may interfere with this potential benefit," write the authors.
These results are consistent with a study published in July in the Archives of Neurology which showed that in a sample of adults aged 65-94, those who ate fish at least once a week had a 60 per cent lower risk of developing the disease compared to those who never or rarely ate fish. The researchers said that a high intake of polyunsaturated fatty acids, found also in nuts and oil-based salad dressings, had reduced the risk of Alzheimer's, although the cause of the debilitating disease which affects an estimated 12 million around the world is still not known.
"These dramatic results show how older adults can play a significant role in their neurological health by increasing their intake of fish, fish oil or especially, DHA," said Dr Ernst Schaefer, senior scientist and director of the Lipid Metabolism Laboratory at Tufts University, and lead author of the new study.
"Until now there have only been two predictors for Alzheimer's Disease, age and genotype," added Henry Linsert, CEO of Martek, the US-based company that supplied its microalgae-derived fatty acids for the research. "This study suggests that low dietary intake of DHA may be a risk factor for Alzheimer's Disease."
DHA is the most abundant fatty acid in the brain. A study published in the British Medical Journal last year found that elderly people who eat fish or seafood even once a week to be at lower risk of developing dementia, including Alzheimer's disease. Omega-3 fatty acids are also being studied for their potential to reduce symptoms of depression.