Capt. Hibbeln, M.D., shares if you should be concerned about the trace levels of mercury found in fish when you are pregnant.
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The Mercury in Fish Concern for Pregnant Women It’s a very important question to ask on a public policy level as to whether or not women should be fearful of trace levels of methyl mercury that are naturally occurring in seafood. And this is especially put to the floor by the 2004 advisory by the Environmental Protection Agency and the FDA, which states that women who are pregnant or fertile or likely to become pregnant should limit their fish intake to 12 ounces a week and avoid four species completely. Now first of all, this advisory is limited to pregnancy. Second of all the message had not been clear that there is no data that methyl mercury from fish has any potential toxicity for anybody else in any other life stage. And furthermore, this advisory from 2004 failed to calculate the nutritional benefits of fish and failed to consider the possibility that this advisory was creating a nutritional deficiency of omega-3 fatty acids delivered to the baby’s developing brains. So it’s a difference in balance between avoiding picomoles, very, very tiny amounts of methyl mercury, compared to losing kilograms of omega-3 fatty acids in the diet. So when the math was done to create the advisory there was a calculation that was heavily weighted and determined by the Faroe Island study where women’s exposure to methyl mercury was from pilot whale and that drove the curve and drove the math. And even in that study there weren’t any clinically significant harms to the children. There were only subtle differences in neurological test scores from that exposure to tenfold as much methyl mercury as women would get from commercial fish. The advisory was designed from a toxicological point of view and a toxicologist is very cautious and they made a curve to figure out what was the lowest detectable limit and then added a tenfold safety factor or uncertainty factor. You know, like you have ten fingers on your hand, that’s good estimate. Then they will apply that to the source of omega-3s which was fish but there was no math done for the bottom end of the curve as to whether or not harm would be created by the deficiency. So a the 2007 paper we published in the Lancet, we asked the specific question as to whether or not the advisory protected as it was intended to do, and we compared women who ate no fish in pregnancy to women who ate a little bit of fish but up to 12 ounces, to the women who ate more than 12 ounces, more than is advised. What we found, we looked at, now the advisory had been calculated on studies of three and four hundred people but we looked in a study of 14,500 women in pregnancies. And what we found is that when women were conforming to the advisory and avoiding fish in pregnancy it nearly doubled the risk that their children would have low IQ at age 8, measured very carefully in neuropsychological testing, doubling the risk, not due to social economic factors, not due to maternal education, not due to anything else but the deficiency of fish in their diet. So the women, the children who did the best unequivocally were the women who were eating more than 12 ounces a week. Now the editors and the reviewers of the article insisted that we put in the phrase that the advisory was detrimental instead of being protective. That’s because it didn’t calculate the nutritional benefits of fish. Since then there have been eight papers published. When people have looked back at the prior studies in the Seychelles, in the Faroe Islands, in New York and looked at this question, maybe we should not just look at the detectable toxicity of methyl mercury. Maybe we should look at fish as a whole net food and figure out what’s better and all of the follow up developmental studies agree with our 2007 Lancet paper that the current advisory is detrimental. The FDA has responded very well at the insistence of, at the suggestion rather of the Institute of Medicine to revisit this risks and benefits question and have reformulated a draft scientific d
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