Increased mercury levels from seafood may not harm the brain

February 8, 2016

A study published in the Journal of the American Medical Association shows that even though mercury levels in the brain increased with seafood consumption, the elevated levels may not be associated with increased brain neuropathologies (i.e., harm to the brain). In fact, the researchers found that seafood consumption was associated with less Alzheimer’s disease neuropathology despite the increased mercury levels.

The study findings were derived from 286 postmortem brain autopsies performed on a cohort of individuals initially free of dementia that the researchers followed for an average of 4.5 years until their death. Tissue concentrations of mercury and selenium were measured using instrumental neutron activation analyses. The participants’ seafood intake was measured by multiple food frequency questionnaires completed in the years before their death. It should be noted that the level of seafood intake in the study population was moderate, and therefore the findings cannot be generalized to populations with higher seafood consumption or to populations with high mercury exposure.

The researchers found that seafood consumption was significantly correlated with less Alzheimer disease pathology, including lower density of amyloid plaques in the brain and less severe and widespread tangles within the neurons. Whereas plaques and tangles are the defining features of Alzheimer’s dementia (characterized clinically by memory loss and decline in other thinking abilities), data suggest that some degree of plaques and tangles accumulate in the brains of most adults, even those without dementia.

In addition, the protective association of seafood was only observed among individuals with a common genotype (APOE-ε4) that increases the risk of developing Alzheimer’s disease.