New NIEHS-supported research showed that some older adults who ate at least one serving of seafood per week showed fewer signs of brain changes related to Alzheimer’s, despite also having elevated levels of brain mercury. The research was published Feb. 2 in the Journal of the American Medical Association.
The group that benefitted from fish consumption had a gene variant known as the APOE4 allele. The finding was notable because this allele, which is found in 15-20 percent of the population, is usually associated with an increased risk of Alzheimer’s disease. Seafood consumption did not change the risk of Alzheimer’s disease in study participants without the APOE4 allele.
Increased brain mercury not linked to Alzheimer’s
Interestingly, because study participants ate more meals of fish per week, the levels of mercury in their brains increased. Yet, higher brain mercury levels were not associated with increased beta amyloid protein plaques and tau protein tangles, which are the hallmarks of Alzheimer’s disease, although mercury can be harmful to the brain and nervous system.
Fish oil supplementation did not have the same protective effect as fish consumption, although only a small group (17 percent) of participants reported taking these supplements.
NIEHS explores how environment and diet interact
The research, conducted at Rush University Medical Center in Chicago, was part of an NIEHS initiative to study how diet can influence potential health effects from exposures to chemicals, such as mercury, in the environment.
“Seafood consumption is promoted for its many health benefits even though it’s contaminated by mercury,” explained Martha Clare Morris, Sc.D., a Rush nutritional epidemiologist who led the study, in a feature article about the paper. “Since mercury is a known neurotoxin, we wanted to determine whether seafood consumption is correlated with increased brain mercury levels in older adults, and also whether seafood consumption or brain mercury levels are correlated with brain neuropathologies.”
Older adults participating in the Memory and Aging Project completed annual dietary questionnaires for a number of years. At the start of the study, all participants were cognitively normal, but some eventually developed cognitive impairment and dementia. The brains of 286 deceased study participants, whose average age was 89.9 years, were analyzed for neuropathologies, or detrimental brain changes, of Alzheimer’s disease and other dementias.
“These findings show that the benefits of moderate seafood consumption may outweigh potential harmful effects in adults,” said Cindy Lawler, Ph.D., head of the NIEHS Genes, Environment, and Health Branch. “We know that seafood consumption benefits cardiovascular health, and the nutrients may also protect against age-related cognitive decline.”
Citation: Morris MC, Brockman J, Schneider JA, Wang Y, Bennett DA, Tangney CC, van de Rest O. 2016. Association of seafood consumption, brain mercury level and APOE-epsilon 4 status with brain neuropathology in older adults. JAMA 315(5):489-497.
(Virginia Guidry, Ph.D., is a technical writer and public information specialist in the NIEHS Office of Communications and Public Liaison.)