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Moderate seafood consumption, despite the mercury risks, might lower the risk for dementia in those at increased risk, an observational study in JAMA suggests.
Researchers studied nearly 290 elders in Chicago who died and underwent brain autopsy. In the years before death, participants provided data on food consumption, including seafood. Two thirds of the autopsied brains had mercury levels measured.

Among those carrying the APOE ε4 allele, which is associated with increased risk for Alzheimer disease, consumption of at least one seafood meal per week was associated with fewer Alzheimer's-related changes at autopsy, relative to less consumption. The effect was not seen in non-carriers of the allele.

Higher seafood consumption also correlated with higher mercury levels, but those levels were not associated with Alzheimer's changes.

JAMA article (Free)