Tuna meltdown
Consumer Reports is telling pregnant women to cut tuna from their diets. So why is the U.S. government casting tuna to poor mothers for free?
By Katharine Mieszkowski

Jun. 22, 2006 | Health claims for tuna just keep getting fishier. The venerable consumer-advocacy group Consumers Union fires the latest salvo in the July issue of its Consumer Reports magazine. Fears that methylmercury, a neurotoxin, can damage a fetus's developing brain led the group to recommend a stringent rule for expectant moms: Lay off tuna entirely.

The magazine advises pregnant women not to eat canned tuna, regardless of whether it's chunk light or albacore. Light tuna is typically found to be lower in mercury than white tuna, aka albacore, so it's often recommended as a more palatable substitute for its more expensive cousin. "For a pregnant woman, even a short-term exposure to a high mercury level is something to be concerned about," says Jean Halloran, director of the Consumer Policy Institute at Consumers Union. "What mercury can do is interfere with nervous tissue connecting up. You don’t want anything to interfere with the hardware of the brain being laid down properly. It’s very much a precautionary measure. We’re not saying if you’ve had a can of tuna fish while you were pregnant you’ve damaged your baby forever."

The new Consumers Union recommendation is based on the group's analysis of data from Food and Drug Administration tests, posted on the FDA's Web site. It's caused quite a stir because it's a departure from the FDA's own fish advisory, which the agency just reaffirmed early this month. The FDA says that women who might become pregnant, are pregnant, or are nursing can eat 12 ounces -- about two average meals -- of light tuna a week. It cautions women to eat half that amount of albacore.

Not surprisingly, the U.S. Tuna Foundation, an industry trade group, disputed Consumer Reports and denounced the magazine on its "Truth About Tuna" Web site, quoting the FDA guidelines. "In an era when heart disease is spiraling and obesity has become an epidemic, Consumer Reports (has) done a great disservice in discouraging canned tuna consumption through inaccurate and incomplete facts," argued Anne Forristall Luke, president of the U.S. Tuna Foundation.

Michael Bender, executive director of the Mercury Policy Project, cites USDA research in saying that canned tuna is "the most heavily consumed fish" by pregnant women and children. The United States is second only to Japan in feasting on the world's prolific tuna catch. There's so much concern about mercury in tuna that California's attorney general, Bill Lockyer, tried -- and failed -- to have warning labels about mercury put on cans of tuna. Whole Foods recently joined Safeway and Wild Oats supermarkets in posting government warnings in stores around the nation about mercury lurking in seafood.

Given the health warnings about tuna, say consumer advocates, it's troubling that the federal government is giving nursing mothers vouchers that can be redeemed for cans of tuna. The USDA's Food and Nutrition Service's Women, Infants and Children program, commonly known as WIC, feeds more than 8 million low-income women and children every month. Women who are pregnant, postpartum or breast-feeding, along with their infants and children up to age 5, are eligible. In addition to food vouchers for staples like milk, cheese and eggs, participants receive counseling on nutrition and breast feeding. The program's reach is so vast that it serves 45 percent of all babies born in the United States, a commentary on how many babies are born into poverty.

Nursing mothers who are exclusively breast feeding their infants in their first year can receive up to 26 ounces of canned tuna per month through WIC. Both albacore and light tuna are eligible, although some states, like Texas, exclude albacore. A nursing infant is not as vulnerable to the toxin as a developing fetus. That's because methylmercury does not pass as easily through breast milk as it does through the placenta and the bloodstream, according to Dr. Leo Trasande, the assistant director of the Mount Sinai School of Medicine's Center for Children's Health and the Environment in New York. Halloran from Consumers Union concurs. "For nursing mothers, the issue still exists, but it’s not as extreme," she says. "Mercury will end up excreted in mother’s milk, but it’s not quite as direct as the passage in the bloodstream from stuff you eat."

Yet, Trasande stresses, there is still some risk to the developing infant's brain, and he recommends that all women of childbearing age -- whether pregnant, nursing or planning to become pregnant -- limit their tuna consumption to about one can per week, whether chunk light or albacore, as long as they're not being exposed to mercury from other fish sources, a recommendation that's more conservative than the FDA's. Consumer Reports offers that women of childbearing age who aren't pregnant eat no more than three cans of chunk light tuna per week or one can of albacore tuna.

Susan Acker, a USDA spokesperson, writes in an e-mail that the program is merely following the FDA's guidelines. She states that the "amount of tuna WIC makes available to exclusively breastfeeding women (26 ounces per month of canned white, light, dark or blended) is within recommended levels." She also says that WIC informs women about the risks of getting too much mercury in their diet by distributing the FDA's guidelines "What You Need to Know About Mercury in Fish and Shellfish" at thousands of WIC clinics. But that message doesn't always get through.

Susan Levin, a nutritionist at the Physicians Committee for Responsible Medicine, a nonprofit group that promotes the health benefits of vegetarian and vegan diets, did a two-week dietetic internship at a WIC office in Seattle in 2004. "They didn't do any education about mercury in fish, and Seattle is a pretty liberal place," she says. "I never saw them talk about the risks behind eating tuna."

Today, the foods offered in the WIC packages are under review, and albacore tuna may be on the chopping block. The National Academies' Institute of Medicine did an official review of WIC's food packages in April 2005, offering guidance on how they should be updated based on the latest nutritional information. It recommends that the program make salmon available to nursing moms as well as light tuna, and that albacore be excluded from the program altogether. The USDA has yet to implement the recommendations.

Some state WIC programs are taking matters into their own hands. Hawaii, which serves more than 30,000 women and children through WIC, persuaded the federal WIC program to allow it to offer canned salmon as well as light tuna -- it doesn't offer albacore at all -- to nursing mothers. Salmon, which eat lower on the food chain than tuna, typically accumulate much less mercury. The WIC program in Hawaii advises nursing mothers about mercury in fish, as well as gives mothers recipes for how to cook with canned salmon, since they may not be as familiar with ways to cook it. Then, the women can choose if they want vouchers for light tuna or salmon. Halloran from the Consumers Union approves of that option: "Almost all canned salmon is Alaska wild salmon. Canned salmon is a good substitute for tuna. It's extremely low in mercury."

Yet even the most aggressive public-health efforts can't get at the root of the real problem -- the pollution from coal-fired power plants that's causing more mercury to show up on our dinner plates.

-- By Katharine Mieszkowski

Mercury in tuna
New safety concerns

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Photocuisine/CorbisCanned light tuna, long recommended as the safer choice because of its presumably lower mercury content, sometimes harbors at least as much of that potentially harmful heavy metal as white tuna does, our analysis of Food and Drug Administration data has shown. That finding raises new concerns about the safety of canned tuna for pregnant women.

We scrutinized the results of FDA tests posted recently on its Web site and, as expected, found that most cans of light tuna had only a third as much mercury, on average, as white tuna, also known as albacore. But 6 percent of the light-tuna samples contained at least as much of the metal--in some cases more than twice as much--as the average in albacore. One possible reason: 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. (But albacore is generally the only species that's labeled.)

The FDA has not warned consumers about those occasionally higher mercury levels because it believes the levels don't pose any significant threat, according to David Acheson, M.D., the chief medical officer at the agency's Center for Food Safety & Applied Nutrition. "If you eat a single can of something that's a little higher than the average, it's not going to do any acute harm," Acheson said when we asked him about fetal safety.

But Consumer Reports' fish-safety experts note that some cans are much higher in mercury than average. And they say there's enough uncertainty about the safety of even brief exposure of the fetus to such higher mercury levels that a more cautious approach is warranted.

To help guide pregnant women and others who wonder whether tuna and other fish are still safe to eat--and if so, how much--here are CR's answers to 10 crucial questions about mercury in fish
Note that all of the following recommendations for weekly or monthly fish consumption assume that no other mercury-containing seafood is eaten during that time.

1. Why should I bother eating fish if there might be risks?

Some fish are safe for everyone (see question 7), and many others can be safely consumed in limited amounts. And seafood is still an important part of a healthful diet. It contains heart-protecting omega-3 fatty acids. It's also a good source of protein and is usually low in saturated fat.

2. What is mercury, and how does it get into tuna and other fish?

Mercury is a heavy metal, naturally present in rocks and soil, that gets into the environment mainly from emissions generated by coal-burning power plants and waste incinerators. Small amounts are also released as soil and rocks break down or during disposal of products that contain mercury, such as fluorescent light bulbs and certain thermometers. Mercury eventually reaches the oceans and rivers, where bacteria convert it to a more toxic form of the metal, which then accumulates in long-lived predatory fish, including tuna. Indeed, consumption of fish is the primary source of mercury in Americans' bodies.

3. Who's at greatest risk from exposure to mercury, and what's the possible harm?

Fetuses and young children appear to face the most risk, because of their small size and the vulnerability of their developing nervous system. Studies of fish-eating populations have linked low-level mercury exposure in pregnant women and young children with subtle impairments in neurological and behavioral functioning, such as hearing, eye-hand coordination, and learning ability. Other evidence suggests that frequent consumption of high-mercury fish by adults may affect the neurologic, cardiovascular, and immune systems.
The effects of sporadic exposure to the higher mercury levels in some light-tuna cans have not been determined. But some scientists are concerned that even brief exposure to those mercury levels at critical points in fetal development may be harmful. For example, studies in primates and rats have shown that mercury blocks the ability of developing brain cells to migrate to the proper place and form appropriate connections. Moreover, our consultants say studies have not established that there's any minimal frequency, duration, or amount of mercury exposure that is safe for the fetus.

4. Should those who are most susceptible to the effects of mercury eat canned tuna?

Based on the FDA data and the mercury- exposure levels that the Environmental Protection Agency deems acceptable, here's what our experts recommend:

Pregnant women. Given the uncertainties about the safety of even chunk-light tuna, we think it's prudent for pregnant women to avoid canned tuna entirely.

Young children (up to about 45 pounds). They 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, depending on their weight. The advice about solid-light is based on limited FDA data suggesting that it may contain considerably more mercury, on average, than chunk-light does, though less than albacore.

Women of childbearing age who aren't pregnant. Mercury can linger in the body after you stop eating fish. So we advise these women to eat no more than about three chunk-light cans per week, or one can of solid-light or white-tuna.

5. How much canned tuna can older kids eat?

It's not clear exactly when children become less vulnerable to mercury; indeed, the brain continues to develop through the teenage years. Nevertheless, government regulators assume that the heavier the child, the more mercury can be safely consumed. Our experts think it's prudent for children weighing anywhere from about 45 pounds to 130 pounds to eat no more than one to three cans of chunk-light tuna per week, depending on their weight. Or they could have one-third to one can of solid-light or white tuna per week.

6. What about canned tuna for men and older women?

The same weekly intake that's considered safe for women of childbearing age who are not pregnant--roughly three cans of chunk-light tuna or one can of solid-light or white--is almost surely safe for men and older women as well. They can quite likely eat more than that without harm, but the exact amounts are not known.

7. Are there any types of fish that are low in mercury?

Some seafood species--salmon, shrimp, clams, and tilapia--have such consistently low mercury levels that everyone, including pregnant women and young children, can safely eat them every day. (Choosing wild salmon minimizes exposure to a number of other pollutants.) 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 fish species (see Low-mercury seafood choices).

8. What about all the other fish--should I restrict my intake of those, too?

Fish other than the low-mercury types listed above should be eaten in more limited amounts or not at all, as follows:

Pregnant women. Follow the FDA recommendation and don't eat tilefish, shark, swordfish, or king mackerel, which are very high in mercury. We further suggest that pregnant women limit their seafood choices to the low-mercury species listed under question 6, for two reasons. Some species--including Chilean bass, halibut, American lobster, and Spanish mackerel--occasionally contain as much mercury as the most contaminated types, such as swordfish. And some fish have not been thoroughly tested for mercury.

Women of childbearing age and all children. They should avoid the same four high-mercury fish that are off-limits to pregnant women. As for other fish, apart from those on our low-mercury list, the amount of the metal they contain varies greatly. Some fish can be safely consumed only once a month, while others can be eaten many times. People who want to be as safe as possible can minimize their consumption of these fish.

Women beyond childbearing age and men. More frequent fish intake, including a very occasional serving of a high-mercury species, is unlikely to cause harm. But studies have not determined the acceptable amounts. To be on the safe side, those people may want to follow the advice for women of childbearing age.

Low-mercury seafood: How much is safe?

This table shows roughly how often pregnant women, other women of childbearing age, and young children can eat certain low-mercury species without consuming more mercury than the Environmental Protection Agency considers safe. Ranges are listed for children to account for differences in their weight. Older children and other adults can almost surely eat more than the corresponding amounts listed below without harm, but the exact quantities are not known. The table includes common fish for which adequate mercury data are available and levels of the metal are consistently low. There are probably other fish that can safely be consumed frequently as well. We plan to publish an update on salmon in a future issue of Consumer Reports. All recommendations below assume that no other mercury-containing fish are consumed during the same week.