A. When Consumer Reports found recently that 6% of the canned light tuna samples it analyzed had as much mercury as the average can of albacore, some people were concerned. What many didn’t take into account was that most of the light tuna tested had one-third of the mercury content of the average can of albacore, and also that the dose of mercury in most fish is too small to harm anyone but a young child or a fetus.
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In 2004, the FDA recommended that young children and women of childbearing age eat up to 12 ounces of lower-mercury fish a week (including canned light tuna, shrimp and scallops), limit their consumption of higher-mercury albacore tuna to 6 ounces per week and totally avoid high-mercury shark, swordfish, king mackerel and tile fish. The intent was to help them maximize intake of omega-3 fatty acids (which are critical to a baby’s brain development) and minimize exposure to mercury (which may thwart healthy growth of the nervous system).
Emily Oken, M.D., M.P.H., has studied both sides of this issue. Her 2005 study in Environmental Health Perspectives linked lower infant cognition with both higher levels of mercury and a lower intake of fish during pregnancy. Oken emphasizes that if a pregnant woman chooses to avoid tuna, she should replace it with other sources of omega-3 fats (salmon, sardines, anchovies, DHA-fortified eggs). Oken, who currently is breastfeeding a seven-month-old, continues to eat light tuna—and to feed it to her 2 1/2-year-old.
Our bottom Line: There’s no scientific evidence that mercury in the fish we eat causes any adverse effects in adults. In fact, not eating fish is a far bigger gamble: “Fish protects against stroke and heart disease—two really big killers,” says Josh Cohen, Ph.D., instructor at The Institute for Clinical Research and Health Policy Studies at Tufts New England Medical Center.