Two recent studies refute the notion that fish and omega-3 fatty acid consumption help prevent dementia.
Most dementias, such as Alzheimer disease, are progressive and incurable. Observational studies over the last 10 years have suggested that adequate fish intake - possibly related to the omega-3 fatty acids in fish - would prevent at least some cases of dementia. Fish are the main dietary source of omega-3 fatty acids.
The Canadian study was relatively small, with 663 participants. They looked mainly at blood levels of omega-3s, and found no association between blood levels of omega-3s and dementia. APOE4 status didn’t matter. For those of you worried about mercury contamination of fish: they found that people with the most mercury in the bloodstream had a lower rate of dementia. Go figure.
Researchers in Rotterdam studied 5395 subjects over almost 10 years. They found no association between dementia and total fish intake, type of fish eaten, and intake of omega-3s.
These results are clearly disappointing for those of us who deal with dementia patients and their families. We’ll see even more dementia as the average age of Western populations creeps higher. Looking at people over 90, about half of them have dementia, and 70% of those are Alzheimer disease that started years earlier.
On the bright side, several studied have associated the Mediterranean diet with lower rates of dementia. It’s looking like that benefit is not related to fish consumption.
Steve Parker, M.D.
Kroger, Edeltraut, et al. Omega-3 fatty acids and risk of dementia: the Canadian Study of Health and Aging. American Journal of Clinical Nutrition, 90 (2009): 184-192.
Devore, Elizabeth, et al. Dietary intake of fish and omega-3 fatty acids in relation to long-term dementia risk. American Journal of Clinical Nutrition, 90 (2009): 170-176.