Canned tuna has lower mercury levels than tuna steaks and sushi, and two canned tuna meals a week is a safe threshold, the FDA says. The agency is currently revising its guidelines about pregnancy and fish consumption; they hope to encourage more pregnant woman and children to eat fish for its many nutritional benefits. At 13 mcg per 4 ounces, light canned tuna lands in their “lower mercury” category, along with others like salmon (2 mcg of mercury for 4 ounces) and shrimp (less than 1 mcg per 4 ounces).
But Philippe Grandjean, MD, a toxin researcher and adjunct professor of environmental health at the Harvard School of Public Health, contends there’s no room for any kind of canned tuna in the diet. “Canned tuna contributes more than one-third of the mercury exposure of the average American,” he says. “About one in six women in coastal U.S. populations have elevated mercury exposures that could cause harm to the fetus.”
He urges people to eat salmon, mackerel and shrimp, which have considerably less mercury than tuna. That recommendation is echoed by Michael Gochfeld, MD, PhD, professor of environmental and occupational medicine at the Robert Wood Johnson Medical School at Rutgers University. “Pregnant women should not eat canned white tuna and should limit canned light tuna,” he says. “They would be much better off choosing canned salmon instead, which is very low in mercury and much higher in beneficial omega 3s.”
Mercury isn’t the only contaminant of concern. The chemical bisphenol A, or BPA, is an endocrine disruptor often present in the linings of canned foods. “Especially in children, diet is the major source of BPA exposure, with the predominant source being canned food consumption,” says Leonardo Trasande, associate professor of pediatrics and environmental medicine at New York University School of Medicine, and author of several recent papers on the health costs of endocrine-disrupting chemicals. Studies show that eating canned foods can increase BPA levels, while eating more fresh food can reduce it.
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