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Mercury may not defeat seafood brain benefits


Seafood is considered an important part 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 the major source of methylmercury, a strong neurotoxin, which when ingested in large amounts can lead to neurocognitive impairment, among other health hazards. Despite potentially concerning levels of mercury, many seafood products also contain selenium, which serves to bind mercury and reduce its toxicity. The question to be answered then is, whether the beneficial effects of omega-3 fatty acids are defeated by the toxicity of mercury ingested with the seafood.

The new study:
The aim 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. For this purpose, 286 autopsied brain specimens from deceased participants at the Rush Memory and Aging Project (MAP) were evaluated. Specimens originated from patients who died between November 2004 and November 2013 and who completed a dietary assessment prior to death. Mercury and selenium were determined in two different brain sections by instrumental neutron activation analysis (INAA). Average brain tissue mercury levels, assessed in 203 brains, ranged from 0.25 µg/g in the inferior temporal region to 0.87 µg/g in the cerebellum and indeed correlated significantly with the participants’ weekly consumption of seafood.

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 e4 carriers. The relationship between seafood consumption and neuropathology was not significant among those without the APOE e4 gene.

Unfortunately, this study was limited by a low proportion of participants having completed 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.

The new study:

Martha Clare Morris, John Brockman, Julie A. Schneider, Yamin Wang, David A. Bennett, Christy C. Tangney, Ondine van de Rest, Association of Seafood Consumption, Brain Mercury Level, and APOE ε4 Status With Brain Neuropathology in Older Adults, JAMA, 315/5 (2016) 489-497. DOI: 10.1001/jama.2015.19451


Related studies:
G. Bjřrklund, Selenium as an antidote in the treatment of mercury intoxication, Biometals, 28/4 (2015) 605-614. DOI: 10.1007/s10534-015-9857-5

J.H. Park, D.W. Lee, K.S. Park, H. Joung, Serum trace metal levels in Alzheimer’s disease and normal control groups, Am. J. Alzheimers Dis. Other Demen., 29/1 (2014) 76-83.  DOI: 10.1177/1533317513506778

E. Oken, J.S. Radesky, R.O. Wright, Ken P. Kleinman, David Bellinger, Chitra J. Amarasiriwardena, Howard Hu, Janet W. Rich-Edwards, Matthew W. Gillman, Maternal fish intake during pregnancy, blood mercury levels, and child cognition at age 3 years in a US cohort, Am. J. Epidemiol., 167/10 (2008) 1171-1181. DOI: 10.1289/ehp.8041

M.J. Berry, N.V. Ralston, Mercury toxicity and the mitigating role of selenium,  Ecohealth., 5/4 (2008) 456-459. DOI: 10.1007/s10393-008-0204-y

M. Weil, J. Bressler, P. Parsons, K. Bolla, T. Glass, B. Schwartz, Blood mercury levels and neurobehavioral function, JAMA, 293/15 (2005) 1875-1882. DOI: 10.1001/jama.293.15.1875

S.R. Saxe, M.W. Wekstein, R.J. Kryscio, Robert G. Henry, Charles R. Cornett, David A. Snowdon, Ford T. Grant, Frederick A. Schmitt, Sara Jean Donegan, David R. Wekstein, William D. Ehmann, William R. Markesbery, Alzheimer’s disease, dental amalgam and mercury, J. Am. Dent. Assoc., 130/2 (1999) 191-199. DOI: 10.14219/jada.archive.1999.0168

D.L. Samudralwar, C.C. Diprete, B.F. Ni, W.D. Ehmann, W.R. Markesbery,  Elemental imbalances in the olfactory pathway in Alzheimer’s disease, J. Neurol. Sci., 130/2 (1995) 139-145. DOI: 10.1016/0022-510X(95)00018-W

Y.K. Fung, A.G. Meade, E.P. Rack, A.J. Blotcky, J.P. Claasen, M.W. Beatty, T. Durham, Determination of blood mercury concentrations in Alzheimer’s patients, J. Toxicol. Clin. Toxicol., 33/3 (1995) 243-247. DOI: 10.3109/15563659509017991

 Related EVISA Resources

Link Database: Toxicity of Organo-mercury compounds
Link Database: Mercury exposure through the diet

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last time modified: February 7, 2016



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