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Researchers at the Rush University Medical Center, Missouri University Research Reactor, and Wageningen University in the Netherlands looked at the autopsied brains of people who had died of natural causes. They found that whether or not a brain had the tangled proteins characteristic of Alzheimer's disease or signs of other diseases that cause dementia depended on genetics, and whether or not the donor of the brain had regularly eaten seafood.
The researchers recruited 544 volunteers in the Chicago area who subsequently died at an average age of 89. These volunteers had "good brains." Despite having grown up in an era in which college education was not the norm, the majority of the volunteers had two years of university-level education or more. Approximately two-thirds were women. Each volunteer was surveyed annually so the researchers could record their dietary choices.The families of 287 of the participants of the study allowed brain autopsies, which revealed striking differences between volunteers who ate seafood and those who did not. Chicago, of course, is an area not known for seafood, and ocean fish and shellfish were not consumed by all of those in the study.
Here's what the researchers discovered:
- The brains of volunteers who ate seafood meals at least once a week had significantly fewer neuritic plaques, which are deposits of toxic proteins in the gray matter.
- The brains of volunteers who ate seafood meals at least once a week had significantly fewer neurofibrillary tangles, which are twisted strings of proteins that form around injured neurons in the brain.
- The brains of volunteers who ate seafood meals at least once a week were significantly less like to show clear physical signs of Alzheimer's disease.
- None of these changes was associated with the use of fish oil supplements, and
- The benefits of fish in the diet for the aging brain was limited to people who had a gene that increases the risk of Alzheimer's called apolipoprotein E (APOE ε4).
However, eating fish has other benefits. The brains of the volunteers who ate fish at least weekly were also less likely to exhibit signs of cerebral macroinfarction, otherwise known as stroke. What protects against stroke seems to be not so much the fatty acids found in fish as the fatty acids found in all kinds of "good fats," both from fish and from health plant oils.
This is not the first study to find that good diet protects against Alzheimer's in people who have the apolipoprotein E gene. Over 20 years earlier, a Columbia University named Jose Luchsinger found that people who had the APOE ε4 gene were much less likely to develop Alzheimer's if they simply consumed fewer calories. "Giving your brain a break" from the constant production of free radicals from food, and avoiding protein consumption long enough (18 hours) to facilitate a detoxifying process called autophagy helped preserve brain function for years longer than expected.