Although federal guidelines suggest younger women and children may safely eat up to 12 ounces of canned light tuna and up to 6 ounces of white tuna a week, Consumers Union is recommending a more cautious approach.


“Canned tuna, especially white, tends to be high in mercury, and younger women and children should limit how much they eat.  As a precaution, pregnant women should avoid tuna entirely,” said Dr. Urvashi Rangan, director of technical policy at Consumers Union, the nonprofit publisher of Consumer Reports. 

In its January 2011 edition, Consumer Reports explains that it tested 42 samples of tuna bought primarily in the New York metropolitan area and online and confirmed that white (albacore) tuna usually contains far more mercury than light tuna.  Canned tuna, the most popular fish in the U.S., is the most common source of mercury in the American diet.

Mercury accumulates in tuna and other fish in an especially toxic form, methylmercury, the advocacy group said, adding that some studies have linked even low-level mercury exposure in pregnant women and young children to subtle impairments in hearing, hand-eye coordination, and learning ability. Consumers Union says other evidence suggests that frequent consumption of high-mercury fish might affect adults’ neurologic, cardiovascular, and immune systems. 

In addition to advising pregnant women to avoid tuna, because of mercury’s potential effects on fetal development, Consumers Union also advises that:

 — Children who weigh more than 45 pounds limit their weekly intake from 4 to 12.5 ounces of light tuna or from 1.5 to 4 ounces of white tuna, depending on their weight.

— Children who weigh less than 45 pounds limit their weekly intake from 0 to 4 ounces of light tuna or from 0 to 1.5 ounces of white tuna, depending on their weight.

In a news release, Consumer Reports said its tests, conducted at an outside lab, found: 

 —  Every sample contained measurable levels of mercury, ranging from 0.018 to 0.774 parts per million.


 — Samples of white tuna had 0.217 to 0.774 ppm of mercury and averaged 0.427 ppm. By eating 2.5 ounces (about half a can) of any of the tested samples, the group noted, a woman of childbearing age would exceed the daily mercury intake that the Environmental Protection Agency considers safe.

 — Samples of light tuna had 0.018 to 0.176 ppm of mercury and averaged 0.071 ppm.  At that average, a woman of childbearing age eating 2.5 ounces would get less mercury than the EPA’s limit, but for about half the tested samples, eating 5 ounces (about one can) would exceed the limit.

Consumers Reports said the Food and Drug Administration has the authority to pull products containing 1 ppm or more of mercury from the market, but never has.

The advocacy group urged FDA to strengthen its current guidance and advise pregnant women to avoid tuna altogether, and called on the agency to test for mercury across the spectrum of fish and seafood in the marketplace in order to provide consumers with adequate information on the levels in all fish.

The group said the last set of FDA data gathered from 2002-2004 and published in 2006 needs to be updated and the sample size of many species should be increased.

Given the uncertainties about the impact of occasional fetal exposure to such high levels, Consumer Reports urged the FDA in 2006 to warn consumers about occasional spikes in mercury levels in canned light tuna. More than four years later, the FDA still hasn’t issued such a warning. When Consumers Union asked why, an FDA spokesman indicated that the agency had already taken the spikes into account when formulating its mercury advice.

Because fish are rich in protein, vitamin D, and omega-3 fatty acids considered especially beneficial during pregnancy, Consumers Union said clams, Alaskan salmon, shrimp, and tilapia contain relatively little mercury and are better choices than canned tuna. Other lower-mercury choices include: oysters, pollock, sardines, Pacific flounder and sole, herring, mullet, and scallops (with some limitations in order for women of child-bearing age and children). 

Federal guidelines also suggest children and women of childbearing age should not only avoid canned tuna but four other high-mercury fish: king mackerel, shark, swordfish, and tilefish.