Image: Can of tuna
How much is too much? Researchers continue to battle over the risks and benefits of tuna.
updated 7/1/2007 3:27:11 PM ET 2007-07-01T19:27:11

Money was tight, what with a baby boy in the house and another one on the way, so Teri Curtis cut costs. The 22-year-old bartender in Bentonville, Arkansas, saved on gas by making fewer trips to see her mother, who lived about an hour away. She and her husband stopped eating dinner out. And for lunch, she almost invariably had a plain tuna sandwich. “It was a cheap meal,” she remembers. “And I thought it would be nutritious.”

Curtis’s second son, Ryker, was born in June 2005, three weeks early. The doctors helicoptered him to a bigger hospital, where he was put in an incubator. The IV the nurses hooked up to his arm kept popping out every time he wriggled, so they inserted one through his scalp. Curtis was able to hold him for only a few hours a day. “On a scale of 1 to 10, I would say I was terrified at an 11,” Curtis says. “That poor kid.” It was a month before Curtis was able to take him home.

There were new problems, though. At 8 months, Ryker wasn’t responding to his name. And he didn’t look at Curtis when she talked to him.

It turned out that Ryker was nearly deaf. His adenoids, clusters of tissue toward the top of the throat, were swollen to the size of an adult’s, clogging up his hearing passageways. What the heck was going on with her child? Curtis wondered. She sat down with her ob/gyn, who ticked off some possible explanations. They could be seeing the health effects of Ryker’s prematurity. Or perhaps it was genetic.

But Curtis had heard something on the news that troubled her. Might mercury be a cause? “It’s unlikely, and we’ll never know for sure,” the doctor told Curtis. “But that might be it.” The toxin is found in certain varieties of seafood — including tuna, which Curtis had eaten at least three times a week for virtually her entire pregnancy. When a pregnant woman consumes mercury, it passes through the placenta into the brain of the fetus, where it can linger for years.

In extreme amounts, more than 10 micrograms per gram as measured in hair (which scientists use to gauge the body’s mercury levels), mercury can cause mental retardation, cerebral palsy, deafness and blindness. In the lower-level amounts typically found in Americans — fewer than 2 micrograms per gram in hair — risks to a newborn include a drop of a few IQ points, slow brain development and learning disabilities. Researchers at the U.S. Environmental Protection Agency estimate that more than 300,000 babies born each year in this country are at risk of having brain damage due to mercury exposure in utero.

Women may also have to worry for their own health: A 2003 study by San Francisco internist Jane Hightower, M.D., published in the journal "Environmental Health Perspectives," found that 89 percent of her female patients had mercury levels above what most scientists consider safe, and that high mercury levels in adults correlated with memory loss, fatigue and muscle aches. Another preliminary study this year found that mothers who delivered prematurely were more likely to have high mercury levels.

Even a suggestion, however remote, that her diet had played a role in Ryker’s illnesses left Curtis devastated. “I felt like everything my son was going through was my fault,” she says. But although she blamed herself, she couldn’t help but wonder why there were no warnings on the cans of tuna she ate. She hadn’t heard anything from the government about limiting tuna during pregnancy, nor did she recall her ob/gyn telling her that tuna might have mercury pollution. “This was something that should never have happened,” Curtis says. “I worry that it could have been prevented.”

Pollution in our seafood
Every day in this country, coal-fired power plants in 46 states spew out particles laced with mercury. Incinerators and chlorine plants burn off still more. The emissions travel on the wind — sometimes hundreds of miles — then fall back to Earth, usually in rain or snow, and land most often in our rivers, lakes and oceans. Though there are natural sources of mercury in the air, such as forest fires, a 2002 study published in "Environmental Science & Technology" estimated that 70 percent of the mercury in our atmosphere was put there by humans.

As it turns out, bacteria in marine soil and sediment like to dine on mercury, which they convert to a toxic form called methylmercury. The bacteria are absorbed by plankton, which fish dine on. Little fish are light eaters, so they don’t consume enough mercury through plankton to become dangerous. But eventually, big fish eat the small fish, and it’s these predators that have the most mercury in their flesh. According to government data, top-of-the-food-chain fish such as shark, swordfish, tilefish and king mackerel contain 0.7 to 1.4 mcg per gram of mercury — anywhere from 8 to 100 times as much as seafood like cod, herring, clams, salmon and scallops.

And then there’s tuna. It has become a focus of mercury worries because we eat so much of it: Canned tuna is the most popular fish in the United States and the second most popular seafood after shrimp, generating close to $1.5 billion in sales annually. That means, as Dr. Hightower notes, “the issue of mercury in fish involves not only the health of the consumer, but the health of the economy.”

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As a large predator fish, tuna contains mercury — and sometimes lots of it. Government data shows that the freshly caught bigeye and ahi tuna used for steaks and sushi has levels around 0.6 mcg per gram, and albacore used to make “white” canned tuna has moderately high levels of about 0.35 mcg per gram. Light canned tuna has long been thought to have low mercury because it’s mostly made from skipjack, a smaller species. But independent laboratory testing of light canned tuna has produced wildly varying levels of mercury even among cans bought in the same store — with some light canned tuna testing higher than tuna steaks.

The task of protecting Americans from mercury in commercially sold fish falls to the U.S. Food and Drug Administration. In its most recent advice to consumers, the FDA recommends that women of childbearing age consume up to 12 ounces — two servings — of fish or shellfish per week. It also says these women should not eat more than 6 ounces of albacore tuna per week. The FDA’s assistant commissioner for food safety, David Acheson, M.D., insists the agency has done a good job warning women about the dangers without frightening them. After all, tuna and many other types of fish are rich in vitamin B and omega-3 fatty acids that prevent heart disease. Eating fish can lower the risk for stroke, depression and mental decline. There are species, including salmon, sole, trout and flounder, that are both high in omega-3s and low in mercury. But Dr. Acheson says that if the FDA issued too dire a warning about tuna, women might turn away from fish altogether and toward fattier, less healthy sources of protein such as red meat.

The tuna industry takes the same position. “We strongly encourage women to follow the advice of the FDA: to eat seafood, including canned tuna, twice per week. They have brought in health professionals from around the nation in a very open and transparent process,” says John Connelly, president of the National Fisheries Institute in McLean, Virginia. This year, the NFI merged with the U.S. Tuna Foundation, a trade group representing the three largest brands of canned tuna. “Large, peer-reviewed, published studies (have found) that without question the best thing young women and families can do is get more seafood into their diet,” Connelly adds.

But has women’s health truly come first in the government’s handling of the mercury issue? For the past decade, numerous scientists have accused the FDA of ignoring their advice and watering down its rules to suit the wishes of Big Tuna: the fisheries that catch and process tuna and the companies that sell it. “It’s been complete and utter foot dragging by the FDA,” says Deborah Rice, Ph.D., a former senior toxicologist at the EPA now working for the state of Maine. At the same time, Big Tuna — and the electrical-power industry that generates mercury emissions in the first place — have put money into scientific studies that found low threats from mercury and have used that research to argue against tighter rules. Leonardo Trasande, M.D., an expert on environmental toxins at the Mount Sinai School of Medicine in New York City, says the result of the country’s lax methylmercury regulations will be felt for decades to come: “Mercury is going to poison an entire generation of our nation’s children.”

Who paid for that mercury study?
The debate started in 1995. Researchers at the University of Rochester School of Medicine in upstate New York reported that they had studied 131 pregnant Peruvian women, who ate fish frequently and had high mercury levels, and found no harm to their babies. As with most studies, you had to read the fine print to see who funded it: the federal government’s National Oceanic and Atmospheric Administration (NOAA), but also Big Tuna: the National Fisheries Institute and the Tuna Research Foundation.

In 1997, another group of scientists reported that mercury in fish was likely nothing to worry about. They took hair samples from American women and tested for traces of mercury. The results, according to the study, did “not justify concern ... of adverse health effects in these women or in their children.” The same industry groups had teamed with NOAA to fund the research, joined this time by the U.S. Tuna Foundation.

But the most reassuring mercury news that year came from an international team including different scientists from the University of Rochester. They had been working in the Seychelles islands off the east coast of Africa, where diets consist mainly of fish. At the time the women studied gave birth, they had about 6 mcg per gram of mercury in their hair — an alarmingly high level. But at a year and a half, the women’s babies showed no ill effects.

The work in the Seychelles was funded by the governments of the United States and the Seychelles, not private industry. Big Tuna and the power industry chipped in the following year, giving some of the Seychelles researchers grants of half a million dollars to evaluate methods of testing children for cognitive defects resulting from environmental toxins, including mercury. In addition to money from an FDA program, the project attracted $5,000 from the fisheries institute, $10,000 from the U.S. Tuna Foundation and $486,000 from the Electric Power Research Institute in Palo Alto, California, a research group funded by electric power–plant companies. (Officials with the EPRI did not return calls for comment.)

There is no evidence that the scientists involved in these studies did anything improper. Their work appeared in peer-reviewed scientific journals and no one has suggested it’s invalid. “There’s been no industry influence on any of the work we’ve done. We report what we find,” says Gary Myers, M.D., professor of neurology, pediatrics and environmental medicine at the University of Rochester. “All of our research in Seychelles has the strict scrutiny and oversight of the National Institute of Environmental Health Sciences. NIEHS is intimately aware of our funding and has never questioned the integrity of our findings or suggested any conflict of interest.”

Yet the fact remains, as Dr. Hightower puts it, that in contrast to studies connected to industry, “most independent studies have found that mercury has harmful health effects.” A 2007 British study published in "The Lancet" was the exception, suggesting that eating seafood while pregnant had a net health benefit for children. But other independent studies in the United States, New Zealand and the Faroe Islands near Iceland have all shown danger to children due to mercury in seafood. The Faroes study, which also appeared in 1997 and was led by Philippe Grandjean, M.D., professor of environmental health at the Harvard School of Public Health in Boston, showed that children born to mothers with elevated mercury levels were slow to develop motor and speech skills. “Over an entire population, it can be significant,” Dr. Grandjean says. “You will have fewer kids who are really bright and will have pushed a few (down so far) they can’t compete in high school.”

By 2000, the federal government had begun to consider how much mercury consumers could safely eat and which fish were most dangerous. The EPA had for years used a low threshold, saying a person could safely ingest 0.1 mcg of mercury per day per kilogram of body weight. For a 132 pound woman, that would mean about 6 mcg a day of mercury — less than is found in one third of a can of light tuna.

The National Research Council in Washington, D.C., one of the nation’s premier scientific bodies, convened a panel of experts to look at the EPA standard in light of the latest research, including the Faroes and Seychelles studies. The independent Faroes research, the panel members wrote in their final report, “should be used as the critical study,” supporting the EPA standard.

But the EPA has jurisdiction only over fish that recreational fishermen catch in the nation’s interior lakes, ponds and rivers. Tuna, which commercial haulers gather on the open sea, falls under the purview of the FDA. And that agency had set a standard five times as high as the one the NRC experts were recommending. Giving equal weight to the Faroes and Seychelles research, the agency issued an advisory in 2001 warning pregnant women against eating king mackerel, shark, swordfish and tilefish. Nowhere did it mention tuna, which accounted for one third of the seafood market.

After the decision, the Environmental Working Group, an activist organization in Washington, D.C., petitioned the FDA to release transcripts from focus groups it had held in fall 2000 on mercury. Those papers show FDA senior scientist Alan Levy, M.D., stating that the standard was “not protective enough” of fetuses, and later suggesting that “it is prudent, particularly for pregnant women, to … moderate their tuna fish consumption.” A draft advisory reportedly did recommend pregnant women eat less tuna. But when the agency released its mercury warning a few months later, all references to tuna had been deleted.

Mercury experts ignored
One spring day a year later, toxicologist Vas Aposhian, Ph.D., did something rare for him: He went food shopping. Aposhian, a professor of molecular and cellular biology at the University of Arizona in Tucson, prefers being in his lab and is content to let his wife do the shopping. But this time he went with her; she pointed him toward what he was looking for. He threw 11 cans of tuna into his shopping cart and the next day mailed them off to a laboratory to be analyzed.

Shortly after, Aposhian flew to Washington, D.C. By this point, the FDA was under intense pressure to reconsider its mercury policies. The public was understandably confused by there being one mercury standard from the EPA and another from the FDA. Meanwhile, many states had drafted their own mercury advisories, some of which were considerably stricter than the FDA’s. The FDA asked its Food Advisory Committee to study the issue further. Aposhian was one of 21 members given this assignment, along with government officials, business leaders, consumer activists and other researchers from around the country.

The committee met in July 2002. About halfway through the deliberations, Aposhian revealed the results of his lab tests: One of the 11 cans he purchased contained 1.24 mcg per gram of mercury, an unsafe level even by FDA rules. It wasn’t a scientific study, but it was all it took to convince Aposhian that young women and their children faced a significant health threat. “I think something has to be done about protecting pregnant women,” he told his fellow committee members.

Other members agreed and urged the FDA to include tuna in its mercury advisory. The committee members’ recommendations were quite specific: They wanted the agency to follow the advisory adopted by the state of Wisconsin — one of the strictest in the nation. That state told women to eat no more than one 6-ounce can of light tuna per week.

Almost two years passed before the FDA updated its advisory. In the intervening time, Big Tuna stepped up its lobbying to new heights, according to data from The Center for Responsive Politics, a group in Washington, D.C., that tracks industry expenditures on lobbying activities such as meetings and meals with lawmakers and regulators. Organizations representing tuna sellers, processors and fishermen spent at least $540,000 lobbying the House, Senate and FDA on mercury and other issues. “There was tremendous regulatory activity during that period, so you would expect to see a spike in contacts between the industry and government,” says Anne Forristall Luke, who was president of the U.S. Tuna Foundation at the time. She adds that the process of crafting the FDA advisory was fully transparent. “The FDA had meetings with industry people, environmental organizations and consumer advocates. There’s nothing nefarious about this kind of lobbying, and the tuna industry advocates for positions it believes are true.”

The Seychelles researchers also joined the debate. The power industry helped underwrite a speech by University of Rochester researcher Philip Davidson, Ph.D., to a July 2003 conference co-hosted by the American Association on Mental Retardation. In his talk, Davidson stressed how little was known about mercury’s health effects. Days later, his colleague Dr. Myers testified before Congress and was less ambiguous, telling lawmakers that “we do not believe that there is presently good scientific evidence that moderate fish consumption is harmful to the fetus.”

The FDA and EPA issued their new joint statement on mercury and fish in March 2004 — and at last tuna was included on the list of fish women should be concerned about. But the agency rejected one of the major recommendations of its own committee: The new mercury guidelines were not modeled on Wisconsin’s. In fact, they were much more lenient. Wisconsin had put the maximum amount of light tuna women should eat at one can per week; the FDA put it at two cans. “It was clear we wanted the Wisconsin numbers followed,” laments consumer advocate Jean Halloran, a member of the committee. “The only way to explain what happened is that the FDA cared most about how an advisory would affect the profits of the fish industry.”

Dr. Acheson says the FDA advisory is based on the best available science, showing that tuna can have both positive and negative health effects. “Not everyone agrees with the tack that we’ve taken, but our role is not to get everyone to pat us on the back. It’s to protect public health,” he says. As for Aposhian, he resigned from the committee in protest the day the FDA issued its decision. “I was shocked the FDA did not follow the Wisconsin advisory,” he says. “It has put the normal development of American children in jeopardy.”

Consumers in confusion
The news about mercury keeps coming, with each contradictory finding seeming to further cloud the picture. Recent research on men in Finland found that mercury in fish increased their risk for heart disease, potentially counteracting the benefits hearts get from omega-3s. Dr. Grandjean, who led the Faroe Islands study, argues that although low-mercury fish is definitely a health food, the evidence linking mercury to heart disease is now strong enough that no one — man, woman or child — should eat fish with elevated mercury levels.

Meanwhile, the tuna industry launched an aggressive marketing campaign aimed at countering the Faroe Islands research. Restaurants and food companies have funded, and magazine ads, all blasting the study as invalid because the residents there get their mercury from whale meat, rather than fish. “Unless you’re lunching on a Moby Dick sandwich, there’s no reason to worry,” one advertisement says. Dr. Grandjean says that “mercury is mercury is mercury. It doesn’t matter if it comes from whale or tuna.” His view is backed by the members of the original 2000 NRC panel, who recently went back and reexamined whether new Seychelles research supplants the Faroes findings. They found it does not.

In May 2006, the seafood industry scored a major victory in court that stopped then California Attorney General Bill Lockyer from requiring tuna companies to warn consumers about man-made toxins in their food, as with labels on cans. Deputy Attorney General Susan S. Fiering called the decision “devastating” to the health of poor women in particular. Testifying against the warnings was Louis Sullivan, M.D., who served as the U.S. Health and Human Services secretary in the early 1990s; Dr. Sullivan, who did not return calls for comment, worked in 2005 and 2006 as a paid consultant to Big Tuna.

The San Francisco judge who ruled against consumer warnings relied heavily on the testimony of François Morel, Ph.D., professor of geosciences at Princeton University in New Jersey, whose findings indicate that very little of the mercury in tuna comes from man-made sources. The state countered in its appeal that Morel’s claims are “not shared by any other scientists in the field.” Morel’s research had been aided by — surprise — the U.S. Tuna Foundation. He says that since 2003, he has also accepted roughly $150,000 a year in grants from the Electric Power Research Institute. The power industry has funded almost all of the research into the chemistry of mercury, he adds. “I’ve yet to see any problems. People are honest and EPRI realizes it would damage itself by trying to skew the results.”

Last October, the Institute of Medicine in Washington, D.C., released a report that Big Tuna declared the best take yet on the issue: Its verdict was that the benefits of eating fish generally outweighed the risks. “Seafood is a good source of high-quality protein, is low in saturated fat and is rich in many micronutrients,” the panel wrote, whereas “the available evidence to assess risks to the U.S. population (from mercury and other pollutants) is incomplete.”

David Bellinger, Ph.D., professor of neurology at the Harvard School of Public Health, was a member of the Institute of Medicine panel. He was also a co-author of a large 2005 Harvard study funded by Big Tuna, including grants from the National Food Processors Association Research Foundation and the Fisheries Scholarship Fund. Bellinger says industry had no influence on his research, which upheld the idea that if pregnant women follow the FDA advisory, their children will have a net health benefit. But would it be better if the Institute of Medicine were able to base its decisions on studies that weren’t funded by industry groups? “In an ideal world?” he replies. “Yes.”

In our imperfect world, the influence of industry-funded research, industry-financed politicians and industry lobbyists makes it difficult for physicians and the consumer to know just whom to trust, says Dr. Hightower, who has treated nearly 100 women for mercury poisoning. “Money tends to add to the confusion when it comes to regulation,” she says. “The public health message is one of compromise for all parties. The doctor’s office should be where the best message is given to patients, regardless of any variable other than health.”

The message she gives patients: Use common sense. Fish such as salmon and flounder, grass-fed beef and fortified products are all good sources of healthy fats. “You can get omega-3 fatty acids without significantly increasing your mercury level and at the same time have a very healthful diet,” she says. “Poison is not a good thing to eat.”

Additional reporting by Kathy Maloney.

Copyright © 2012 CondéNet. All rights reserved.


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