While seafood contains many important nutrients for brain function – including omega-3 fatty acids such as DHA (docosahexaenoic acid) – some fish can be high in mercury, which is an element known to impair development of the brain. Because of this connection, researchers from the Rush University Medical Center in Chicago set out to determine whether mercury from fish could have an effect on the development of Alzheimer’s disease.
The research – led by Martha Clare Morris – used data collected from patients who participated in the Memory and Aging Project clinical neuropathological cohort study, between 2004 and 2013. Five hundred and fifty four people – 67 percent of which were women – were part of the study.
Participants’ seafood intake was measured using a self-report questionnaire for approximately 4.5 years before death. Out of the over 500 participants, 286 of them underwent brain autopsies after death.
The researchers found that consumption of at least one seafood-containing meal per week was correlated with a decrease in the pathological symptoms of Alzheimer’s disease, including less severe neurofibrillary tangles and lower neuritic plaque density. This correlation was only identified among patients with a gene variant which may confer an increased risk of developing Alzheimer’s disease – known as apolipoprotein E.
Although those with more seafood in their diet had higher levels of mercury in the brain, the increased levels of the neurotoxin were not linked with neuropathology. Interestingly, participants taking a fish oil supplement did not show increased or decreased levels of neuropathological markers.
“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,” said the researchers. This study is the first of its kind to examine the link between Alzheimer’s neuropathology, brain mercury concentration and diet.
The design of the study does pose some limitations in terms of data interpretation. Since the research relied upon self-reporting measures, Morris and her colleagues were unable to infer causality between seafood consumption, mercury levels in the brain and neuropathology. In addition, participants consumed moderate levels of seafood so any results cannot be extrapolated to populations that consume large amounts of seafood, or whose seafood contains higher levels of mercury.
“A major concern in public health was whether the increased mercury exposure that comes from consuming seafood might have harmful effects on the brain as we age,” Morris said in an interview with Medical News Today. “This study provides evidence that the increased mercury exposure is not correlated with increased brain pathologies associated with dementia.”