As a prudent measure, Consumer Reports is cautioning pregnant women to avoid canned tuna. The magazine's advice is based on an analysis of Food and Drug Administration (FDA) tests of mercury in fish posted recently on the agency's Web site.
CR's analysis of government data showed that six percent of the tested samples of canned light tuna, long recommended as the safer choice over white tuna (also known as albacore) because of its presumably lower mercury content, contained at least as much or more of that potentially harmful heavy metal as white tuna. One possible explanation is that some canned light tuna may contain yellowfin, which tends to have much more mercury than skipjack, the type usually found in cans labeled as light. Also, limited FDA data suggested that between chunk-light and solid- light tuna, the solid-light may contain more mercury, on average, than chunk-light.
"Based on the FDA's test results and the guidelines for acceptable levels of exposure to mercury set out by the Environmental Protection Agency (EPA), we believe that it's prudent for pregnant women to avoid canned tuna and for young children and women of childbearing age to limit consumption. Exposure to mercury from fish can result in small but measurable impairments in the neurological system, including such problems as eye-hand coordination and learning ability," says Dr. Marvin M. Lipman, Consumer Reports' Chief Medical Adviser.
"Fortunately, there is a wide variety of low-mercury seafood options that everyone can eat frequently as part of a healthy diet. Fish is an important source of protein and contains heart- protecting omega-3 fatty acids," adds Dr. Lipman.
In light of FDA's posted data and the EPA's reference dose for mercury in fish, CR's experts offer advice for the following groups of people:
Everyone (including pregnant women and young children): Salmon (specifically wild salmon), shrimp, clams, and tilapia have such consistently low mercury levels that everyone can safely eat them every day. Other low-mercury species, including oysters, hake, sardines, crawfish, pollock, herring, flounder, sole, mullet, Atlantic mackerel, scallops, crab, and Atlantic croaker, can be consumed anywhere from once a week to daily, depending on body weight, and the type of fish.
Pregnant women: CR advises pregnant women to choose only from low-mercury species and completely avoid tilefish, shark, swordfish, and king mackerel, which are very high in mercury. Avoiding other types is prudent because some species such as Chilean bass, halibut, American lobster, and Spanish mackerel occasionally contain as much mercury as the most contaminated types. In addition, mercury levels in other species have not been thoroughly tested.
Young children up to 45 pounds: Depending on their weight, young children can safely eat about one-half to one 6-ounce can (roughly 4.5 ounces drained) of chunk-light tuna per week, or up to one-third of a can of solid-light or white-tuna.
Older children weighing anywhere from 45-130 pounds. Government regulators assume that the heavier the child, the more mercury can be safely consumed. That said, CR's experts believe that these children should eat no more than one to three cans of chunk-light tuna per week or one-third to one can of solid-light or white tuna depending on their weight.
Women of childbearing age who are not pregnant: CR advises these women to eat no more than about three chunk-light cans per week, or one can of solid-light or white-tuna.