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The View from New York, By Ned GrothAmericans and Their Food, Part 4: Tuna rots your brainMost people in Europe and America know that eating fish is good for you. Diets rich in fish and seafood reduce the risk of heart attack or stroke, and fish really is “brain food.” Nutrients in some fish are essential for brain development before birth and in the first few years of life. But fish-eating has a “dark side,” too. We have learned not to buy some popular species, to reduce unsustainable fishery exploitation. Fish and shrimp farms are notorious sources of pollution and can destroy tropical wetlands. And of course, there is methylmercury. Mercury pollutes the seas from natural and human sources. Bacteria convert it to organic methylmercury, which accumulates in the food chain. Predatory open-ocean species like tuna, swordfish, shark and marlin contain especially high levels. The only significant way people are exposed to methylmercury is by eating fish. Too much exposure damages the nervous system, first documented in residents of Minamata, Japan, in the 1950s. The Minamata incident involved intense industrial mercury pollution, but research in the past 20 years shows that “ordinary” methylmercury exposure, from a high-fish diet, can damage a developing baby’s brain. A Harvard study published early this year found that the amount of mercury in just two fish meals per week, eaten when women were pregnant, damaged cognitive development in the women’s babies. Eating fish also helped the babies’ brains develop properly, but the more mercury the women got with their fish, the less well their children did on tests of memory, learning and fine-motor coordination. Babies aren’t the only ones we need to worry about. An Italian study in 2004 compared men who ate a lot of tuna fish and had moderately high levels of mercury in their blood with others who had very low blood mercury. The tuna lovers felt fine and had no signs of Minamata disease. But they scored significantly less well on several tests of memory, mental processing and fine coordination than the controls did. Sensitive tests can detect toxic effects of methylmercury even in adults with no symptoms. More obvious mercury poisoning has also been reported occasionally in American adults who eat a great deal of fish and whose favorite choices are high-mercury species such as tuna, swordfish, halibut or sea bass. The scientific bottom line is an obvious, common-sense conclusion: People, including moms-to-be, should still eat plenty of fish. But they should choose low-mercury fish. In 2004, our government updated its advice to consumers on mercury in fish. The current advice is for women of childbearing age. It emphasizes the nutritional benefits of eating fish, urges women to eat up to 12 ounces (two servings) a week, warns them to avoid four very high-mercury fish varieties and to limit consumption of tuna fish (the largest source of mercury in the US diet), and lists low-mercury seafood choices. It might surprise Europeans to hear that this good, sensible, scientifically sound advice—something rare from the Bush Administration—has been intensely controversial here, and has led to an all-out public-relations war. The US fishing industry, especially the tuna industry (whose market share has been shrinking for years despite steady growth in US per capita fish consumption) is afraid information about mercury risks will hurt their sales. They have worked very hard to confuse consumers and undercut the government’s advice, promoting the message “eat more fish” while asserting that mercury information is just “hype” and “scare tactics” and that there is no actual risk. It seems to me that scientific consensus is generally respected in Europe, but here in America, the party with the loudest voice, not the soundest science, often prevails. The industry campaign has had the desired effect; most Americans are confused about mercury. The government and NGOs keep communicating the facts, but we are often drowned out by commercial disinformation. Sometimes life is easier on that side of the Atlantic. That’s my view about mercury in fish, from New York For More Information:
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Ned Groth |
