<\/p>\n
Brought to you by\u00a0Deepak Chopra, MD,<\/a>\u00a0Alexander\u00a0Tsiaras, and TheVisualMD.com<\/a><\/p>\n<\/div>\n <\/p>\n<\/div>\n When you order fish in a restaurant these days, you might feel you need a marine biologist to help you make your selection\u00a0rather than\u00a0a waiter. Figuring out which fish is safe to eat\u2014and how often\u00a0you should eat fish\u2014has become fraught with worry, mainly due to concerns about mercury content. You might be tempted to swear off\u00a0seafood\u00a0completely to\u00a0keep\u00a0things\u00a0simple. But if you do, you\u2019ll miss out on the\u00a0health benefits of eating fish<\/a>, including the heart-healthy omega-3 fatty acids in many fish. A wiser approach is to understand why mercury is a concern and when to avoid certain seafood.<\/p>\n <\/p>\n<\/div>\n Where the mercury comes from\u00a0How\u00a0does mercury get into fish and shellfish in the first place? Mercury is a metal that occurs naturally in several forms. The kind inside your thermometer is called elemental or metal mercury. It\u2019s used to make dental fillings and some batteries. It\u2019s also used in\u00a0chemical manufacturing plants<\/a>, coal burning plants, and other industries, and that\u2019s how it ends up in your swordfish steak.\u00a0Industrial pollution releases elemental mercury into the air<\/a>. Rain then washes the mercury out of the air and into streams and oceans where it gets turned into methylmercury. Fish and shellfish absorb methylmercury as they feed and it builds up in the animals\u2019 tissues over time. That\u2019s why larger and older fish tend to have the most mercury.<\/p>\n <\/p>\n<\/div>\n Risks to the developing nervous system\u00a0Most of our exposure<\/a>\u00a0to mercury comes from the methylmercury in contaminated fish.\u00a0Ingesting excessive amounts of mercury is not good for anyone. In adults, it can cause damage to the\u00a0nervous system, as well as the immune system and\u00a0heart<\/a>. But the greatest health risk from the mercury in seafood is to\u00a0fetuses, infants, and very young children<\/a>. Even small amounts of mercury in a pregnant or nursing woman\u2019s blood can damage the developing nervous system of a fetus or infant.\u00a0Nerve cells multiply and grow at a rapid rate during gestation and infancy and are especially sensitive to mercury.\u00a0Scientists aren\u2019t sure exactly how the metal does its damage, but they\u00a0think that it may\u00a0stop the growth of dendrites and axons<\/a>, the fibers on the cells that deliver and receive signals.\u00a0Studies<\/a>\u00a0of populations that consume large amounts of seafood have found that children who were exposed to methylmercury in the womb or shortly after birth had altered memory, attention, and language development.<\/p>\n <\/p>\n<\/div>\n So how much mercury is too much? Scientists don\u2019t know precisely what level of mercury in the blood leads to harmful effects.\u00a0Studies<\/a>\u00a0show that children suffer developmental delays when their mother\u2019s blood level is as low as 30 to 40 ng\/mL (nanograms per milliliter), while adults usually don\u2019t show symptoms of mercury poisoning until their levels are higher. Fortunately, most people have some\u00a0built-in\u00a0protection against mercury: A genetically determined mechanism causes the body to expel\u00a0the metal\u00a0in 30-40 days. A\u00a0Swedish biologist<\/a>\u00a0recently discovered that a small portion of the population carries a genetic mutation that makes their cells retain mercury much longer\u2014in rare cases up to 190 days\u2014and those people may be at higher risk.<\/p>\n<\/div>\n While mercury poisoning from eating seafood is relatively\u00a0rare<\/a>, the\u00a0early signs<\/a>\u00a0include tingling and numbness in fingers and toes and poor muscle coordination.\u00a0The\u00a0treatment<\/a>\u00a0for mercury poisoning caused by eating contaminated fish is simple: You stop eating the fish and wait for levels to come down naturally.<\/p>\n <\/p>\n<\/div>\n Guidelines for eating seafood\u00a0Of course a better solution is to avoid ingesting too much mercury in the first place. That\u2019s easy to do. For most adults, eating fish and shellfish is not a health risk\u2014and it\u2019s important to get the\u00a0health benefits<\/a>\u00a0of fish. Seafood is an excellent source of high-quality protein and iron, and it\u2019s low in saturated fat. And fish that are high in omega-3 fatty acids, such as trout, salmon, and tuna, can lower your risk of heart attack and other cardiovascular problems. That\u2019s why the\u00a0American Heart Association<\/a>\u00a0recommends eating at least two servings of fish a week.<\/p>\n <\/p>\n<\/div>\n However, women who may become pregnant or are already pregnant, nursing mothers, and young children need to be more careful. The\u00a0FDA<\/a>\u00a0advises pregnant or nursing women to avoid four fish that contain high levels of mercury: shark, swordfish, king mackerel, and tilefish. Instead, they should eat up to 12 ounces a week of fish and shellfish that are lower in mercury. These include shrimp, canned light tuna, salmon, Pollock, and catfish. If you eat canned albacore (\u201cwhite\u201d) tuna, limit your intake to 6 ounces per week because it has higher mercury content. Young children should eat smaller portions of these fish.<\/p>\n <\/p>\n<\/div>\n While pregnant and nursing women should avoid high-mercury fish, they should\u00a0not\u00a0stop eating seafood, according to the FDA and others. That\u2019s because fish and shellfish contains nutrients\u00a0that are important for a baby\u2019s growth. Plus, the omega-3 fatty acids in many fish can actually promote the baby\u2019s\u00a0brain development<\/a>\u00a0(they help adult brains function better, too). So next time you\u2019re ordering fish, don\u2019t panic. Just make sure you eat a variety of seafood (not a steady diet of the four high-mercury fish) and follow the guidelines if you are pregnant or nursing.<\/p>\n <\/p>\n<\/div>\n\n\n\n\n\n\n\n\n\n