Tuna Safety

In March of 2004 the Food and Drug Administration and the Environmental Protection Agency recommended that sensitive populations—women who are pregnant or might become pregnant, nursing mothers, and young children—should avoid eating large ocean fish like swordfish, tilefish, king mackerel, and shark. But what about the most commonly eaten fish, like tuna? Canned tuna is eaten by 96 percent of American households, and represents the number three item in U.S. grocery stores (behind sugar and coffee) based on dollar sales per linear foot of shelf space.

Santerre used a mercury analyzer to test over 250 cans of fish, including five brands of tuna, two brands of salmon, and two brands of mackerel for mercury. (The four types of tuna were light tuna in water, light tuna in oil, white/albacore tuna in water, and white/albacore tuna in oil.) He also tested them for levels of omega-3s. He found that salmon and mackerel were lower in mercury and higher in omega-3s than tuna, and that white/albacore tuna tended to have higher levels of mercury than chunk light tuna, though the white/albacore was also higher in omega-3s. "There are types of tuna, for us it was chunk light tuna in water, that had extremely low levels of mercury, as low as you would find in a salmon or mackerel product," he says. "We would recommend that these be eaten by pregnant women, nursing women, young children." Santerre says the albacore tends to be higher in mercury because, "as I understand it, they'll be an older fish, maybe a different species, and so they'll be exposed to mercury throughout their life and so they'll accumulate more."

image: ABC News

Santerre cautions that even women who might become pregnant are considered part of the sensitive population. "A woman that may become pregnant must understand that mercury can stay in her body for up to a year, so it's very important for her to take steps prior to her becoming pregnant to keep the mercury out of her body," he explains, but stresses that people should not be scared away from eating fish. "It's very important that people eat fish. We recommend about 8 ounces of fish a week to get those healthy nutrients that are found in fish, so that's very important. For pregnant, nursing women, young children, be careful about which fish you incorporate in to the diet. We recommend fish that's high in omega-3s and low in mercury. Salmon…is a very good choice, rainbow trout is another good choice, shrimp is a reasonably good choice."

Santerre, who is also a food science communicator with the nonprofit Institute of Food Technologists, says that more accessible mercury testing is in our future. "One of the revolutionary things that's occurred in the last three or four years is we've gotten better ways, faster ways of measuring mercury in fish," he says. "The mercury analyzer is capable of testing hair, cuticles and blood and potentially milk, so at some point we will have more widely available testing of mercury that people will have access to."

Next, Santerre is looking at the mercury content of fast food fish sandwiches. This research appeared in the December 15, 2004 issue of the Journal of Food Science, and was funded by the Purdue University Center for Food Safety Engineering.