Selenium Health Benefit Values as Seafood Safety Criteria |
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Authors: | Nicholas V C Ralston |
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Institution: | (1) Energy & Environmental Research Center, University of North Dakota, 15 North 23rd Street, Grand Forks, ND 58202-9018, USA |
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Abstract: | Selenium (Se) is absolutely required for activity of 25–30 genetically unique enzymes (selenoenzymes). All forms of life that
have nervous systems possess selenoenzymes to protect their brains from oxidative damage. Homeostatic mechanisms normally
maintain optimal selenoenzyme activities in brain tissues, but high methylmercury (MeHg) exposures sequester Se and irreversibly
inhibit selenoenzyme activities. However, nutritionally relevant amounts of Se can replace the Se sequestered by MeHg and
maintain normal selenoenzyme activities, thus preventing oxidative brain damage and other adverse consequences of MeHg toxicity.
Findings of studies that seem contradictory from MeHg exposure perspectives are entirely consistent from MeHg:Se molar ratio
perspectives. Studies that have reported dose-dependent consequences of maternal MeHg exposures on child development uniformly
involved seafoods that contained much more Hg than Se. Meanwhile more typical varieties of ocean fish contain much more Se
than Hg. This may explain why maternal MeHg exposure from eating ocean fish is associated with major IQ benefits in children
instead of harm. Therefore, instead of being avoided, ocean fish consumption should be encouraged during pregnancy. However,
the safety of freshwater fish consumption is less certain. In freshwater fish, MeHg bioaccumulation and toxicity are both
inversely related to Se bioavailability. Their Se can be far lower than their MeHg contents, potentially making them more
dangerous than pilot whale meats. Therefore, to provide accurate and appropriate regulatory advice regarding maternal consumption
of seafoods and freshwater fish, Hg:Se molar ratios need to be incorporated in food safety criteria. |
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Keywords: | brain selenium seafood fish mercury toxicity |
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