Fish Oil and Alzheimer's Disease, Dementia

Fish Oil Supplements Contain EPA and DHA

PARIS, FRANCE. Several epidemiological studies have shown that a high dietary intake of linoleic acid and a low intake of fish oils (eicosapentaenoic acid [EPA] and docosahexaenoic acid [DHA]) are associated with cognitive impairment and an increased risk of dementia. French researchers now report that the fatty acid composition in erythrocytes (red blood cells) is an indicator of the risk of cognitive function decline (ability to learn, think and remember). What is the relationship between fish oil and the brain’s cognitive function?

Their study involved 246 men and women (aged 63 to 74 years) who had the lipid (fatty acid) composition of their erythrocytes analyzed in 1995. All participants also underwent tests to determine their cognitive function at baseline and after a 4-year follow-up period. The researchers found that study participants with high erythrocyte levels of stearic acid (a saturated fatty acid) had a 91% higher risk of having experienced a significant decline in cognitive function over the 4 years than did participants with average levels. Participants with high levels of linoleic acid (an unsaturated omega-6 acid) had a 59% increased risk of decline while those with high levels of EPA and DHA had a 41% lower risk of experiencing cognitive decline than did those with normal levels.

EPA and DHA Are Good for the Brain

The researchers suggest that the omega-3 fatty acids EPA and especially DHA (both found in fish oil) help keep the membranes of brain cells more fluid while saturated and omega-6 fatty acids tend to "harden" them. They believe this and the anti-inflammatory effects of EPA and DHA are what help preserve the brain’s cognitive function.
Heude, Barbara, et al. Cognitive decline and fatty acid composition of erythrocyte membranes – The EVA Study. American Journal of Clinical Nutrition, Vol. 77, April 2003, pp. 803-08

Editor's comment: Stearic acid is found in high quantities in beef, mutton, and pork while omega-6 fatty acids are abundant in vegetables oils such as safflower, sunflower, and soybean oil. The long-chain omega-3 fatty acids (EPA and DHA) are found in fatty fish and fish oils.

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