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Elderly reduce risk of Alzheimer’s eating seafood with no worry of mercury

Red fish on ice at seafood marketSeafood fights dementia; mercury contamination not related to increased brain pathology

Feb. 6, 2016 - In a study of the brains of deceased elderly people, moderate seafood consumption was associated with less Alzheimer’s disease neuropathology, and although seafood consumption was associated with higher brain levels of mercury, the higher mercury levels were not linked to more Alzheimer disease neuropathology.

Numerous studies have found seafood consumption appears to offer some protection from dementia. Dementia is a loss of brain function that occurs with certain diseases. Alzheimer disease (AD) is one form of dementia. It affects memory, thinking, and behavior.

Before this study, however, little has been known about the relationship between seafood consumption and brain neuropathology. It is published in the February 2 issue of JAMA.

Neuropathology, according to Wikipedia, is the study of disease of nervous system tissue, usually in the form of either small surgical biopsies or whole autopsies. Neuropathology is a subspecialty of anatomic pathologyneurology, and neurosurgery. It should not be confused with neuropathy, which refers to disorders of the nerves (usually in the peripheral nervous system).

Seafood is a source of mercury, a neurotoxin that is known to impair neurocognitive development. Mercury toxicity is reduced by selenium, an essential nutrient present in seafood.

The question of whether seafood consumption is correlated with increased brain mercury levels and, whether seafood consumption or brain mercury levels are correlated with brain neuropathologies were goals of the research by Martha Clare Morris, Sc.D., of Rush University Medical Center, Chicago, and colleagues.

The study included analyses of deceased participants in the Memory and Aging Project clinical neuropathological cohort study, 2004-2013. The average age at death was 90 years and 67 percent were women. Seafood intake was first measured by a food frequency questionnaire at an average of 4.5 years before death.


Among the 286 autopsied brains of 544 participants, brain mercury levels were positively correlated with the number of seafood meals consumed per week.

In models adjusted for age, sex, education, and total energy intake, seafood consumption (one or more meal[s]/week) was significantly correlated with less Alzheimer disease pathology. This included lower density of neuritic plaques, less severe and widespread neurofibrillary tangles and lower neuropathologically defined Alzheimer disease, but only among apolipoprotein E (APOE ε4) carriers, a gene variant associated with an increased risk of developing Alzheimer disease.

Fish oil supplementation had no statistically significant correlation with any neuropathologic marker.

Although seafood consumption was correlated with higher brain levels of mercury, the higher mercury levels were not significantly correlated with increased levels of brain neuropathology.

The authors note that the findings were from a very old, largely non-Hispanic white cohort and may not be generalizable to younger adults or other racial or ethnic groups.

 “To our knowledge, this is the first study to report on the relationship between brain concentrations of mercury and brain neuropathology or diet. The finding of no deleterious correlations of mercury on the brain is supported by a number of case-control studies that found no difference between Alzheimer disease patients and controls in mercury concentrations in the brain, serum, or whole blood.”

This study was supported by grants from the National Institutes of Health. 

JAMA Editorial:

Fish Consumption, Brain Mercury, and Neuropathology in Patients With Dementia

 “Patients and their families may be hopeful that interventions such as seafood consumption may help reduce clinical manifestations of Alzheimer disease or dementia, and the report by Morris et al provides reassurance that seafood contamination with mercury is not related to increased brain pathology,” write Edeltraut Kroger, Ph.D., and Robert Laforce Jr., M.D., Ph.D., of Universite Laval, Quebec City, Quebec, Canada, in an accompanying editorial.

 “Eating fatty fish may continue to be considered potentially beneficial against cognitive decline in at least a proportion of older adults, a strategy that now generally should not be affected by concerns about mercury contamination in fish.

“Such a simple strategy is encouraging in the light of the lack of evidence on protection against many neurodegenerative diseases such as Alzheimer disease and Parkinson disease, another cause of dementia.”

>> The research study

>> Watch this video about Alzheimer’s disease


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