1. Seafood consumption (>1 meal/week) associated with decreased Alzheimer disease neuropathology among apolipoprotein E (APOE ε4) carriers.
2. Cortical mercury and selenium levels were positively correlated with the number of seafood meals consumed per week.
Evidence Rating Level: 3 (Average)
Study Rundown: Seafood consumption is considered a mainstay of many healthy diets, particularly due to its macronutrient make-up, high in levels of the long-chain omega-3 fatty acids. However, seafood is also known to be a source of mercury, a neurotoxin, which when ingested in large amounts can lead to neurocognitive impairment, among other ailments. Despite potentially concerning levels of mercury, many seafood products also contain selenium, which serves to bind mercury and reduce its toxicity. With all of these potentially overlapping effects of seafood on neurological health, the purpose of this cross-sectional analysis was to study the association between neuropathologies like Alzheimer disease, dietary omega-3 fatty acids, and brain levels of mercury and selenium.
The study found that seafood consumption was indeed correlated with higher brain levels of mercury. However, mercury levels were not significantly associated with increased brain neuropathology. Overall an increased seafood consumption was associated with less Alzheimer pathology among those at the greatest risk of developing Alzheimer disease—APOE ε4 carriers. The relationship between seafood consumption and neuropathology was not significant among those without the APOE ε4 gene. This study was limited by a low proportion of participants completing the dietary questionnaires and a relatively narrow demographic spread. However, it is one of the first investigations into the effect of mercury levels on brain neuropathology. Future studies should widen the sample population while strengthening the number of participants with both dietary and pathological data.
In-Depth [cross-sectional study]: This cross-sectional analysis evaluated 286 autopsied brain specimens from deceased participants at the Rush Memory and Aging Project (MAP). Specimens were included among patients who died between November 2004 and November 2013 and who completed a dietary assessment prior to death. Brain cortical mercury levels were positively correlated with the number of seafood meals consumed per week (ρ 0.16, p = 0.02). After adjusting for age, sex, education, and total energy intake, seafood consumption was significantly correlated with decreased risk of neuropathologically defined Alzheimer disease among APOE ε4 carriers (β −0.53 score units; 95%CI −0.96 to −0.10). Of note, further increases in omega-3 fatty acid supplementation was not correlated with any changes in the risk of Alzheimer pathology.
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