Moms-to-Be: Don't Eat These Fish

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To avoid passing on certain harmful chemicals to their children, potential mothers may need to fast from fish for many years, according to a new study. Environmental scientists recently calculated how long a woman would need to avoid eating fish to reduce the amount of persistent organic pollutants (POPs) that she may pass on to her offspring.

After one year of replacing fish with vegetables in her diet, a woman would only reduce by 9 percent her child’s prenatal exposure to a POP called polychlorinated biphenyl-153 (PCB-153). Five years of substituting veggies for fish could reduce prenatal POP exposure by 37 percent. A potential mother could reduce her future child’s prenatal exposure by 85 percent if she replaces fish with veggies for 30 years prior to childbirth. The journal Environmental Health Perspectives published the results of the scientists’ models.

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In people, POPs have been linked to reproductive, developmental, behavioral, neurologic, endocrine and immunologic adverse health effects, according to the Environmental Protection Agency.

Current U.S. Food and Drug Administration guidelines aim to reduce mothers’ intake of methylmercury from fish, not POPs. Mercury can harm an unborn baby’s nervous system. Mercury builds up in the food chain, so expectant and nursing mothers should especially avoid eating predatory fish, such as shark, swordfish and king mackerel. However, mercury naturally clears out of a woman’s system after approximately one year in most cases.

POPs, including the banned pesticide DDT, also build up in the food chain. Unlike mercury, POPs don’t easily flush out of humans or animals. The chemicals build up in an animal’s fat, then are passed on to whatever predator dines on that fat. Predators at the top of the food web — including humans — end up with the heaviest loads of pollutants.

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“We have to be careful in saying fish advisories don’t work at all because they can work very well for reducing exposure to quickly eliminated contaminants, such as mercury,” said lead author Matthew J. Binnington, doctoral candidate at the University of Toronto. “But for POPs we found that they are not very effective.”

Despite the potential for passing on pollutants, fish and shellfish also contain high-quality protein and omega-3 fatty acids that benefit children’s health. To avoid the contaminants, yet get the health boost, people can eat seafood known to be generally low in pollutants, including shrimp, canned light tuna,  pollock and catfish, according to the FDA.

Photo: Fish for sale at Tsukiji fish market, Tokyo. Credit: Michael Maggs, Wikimedia Commons

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