Consumer advocates are again urging the government to advise pregnant women to limit tuna consumption, arguing that some varieties contain more potentially harmful mercury than others.
The Food and Drug Administration has no plans to explicitly warn women of childbearing age off tuna when it issues new consumer advice on mercury in fish next spring.
But officials argue that women who closely follow the recommendations will self-limit consumption by default _ and the agency will ask its scientific advisers this week if that's sufficient.
Fish, including tuna, is very nutritious. Many species contain certain fats called omega-3s that are very heart-healthy and important for fetal brain development. The American Heart Association recommends eating fish twice a week.
But fish also can harbor mercury, a metal that accumulates in the bodies of fish-eaters and can damage the growing brains of fetuses and young children. About 8 percent of U.S. women of childbearing age have enough mercury in their blood to put a fetus at risk.
Some fish varieties harbor more mercury than others. The FDA has long told women who may become pregnant to avoid shark, swordfish, king mackerel and tilefish.
But the FDA in 2001 said a few servings a week _ totaling 12 ounces _ of any other fish is healthy during pregnancy. That sparked fierce criticism from consumer advocates who argue that tuna, with moderately high mercury levels, is eaten so often by pregnant women and young children that it needed warnings, too.
In 2002, the FDA's own advisers recommended saying that two 6-ounce cans of tuna a week is fine if that's the only fish pregnant women eat; a single can is OK if they eat other fish, the agency said.
The FDA released its new fish testing data on Wednesday, showing that more expensive white, or albacore, canned tuna contains almost three times as much mercury as cheaper "light" canned tuna _ 0.358 parts per million vs. 123 ppm.
Drafts of new consumer advice the agency is planning don't spell out that difference. Instead, the FDA plans to tell pregnant women that mercury levels in tuna vary and that tuna steaks and canned albacore "generally contain higher levels of mercury than canned light tuna."
But the new advice stresses eating a variety of fish to make up the 12 weekly ounces _ not the same type, whether it's tuna or any other species, more than once a week, said FDA medical officer Dr. David Acheson.
Still, not singling out limits for tuna prompted consumer advocates' outcry.
"They've completely failed in their obligation to protect the public," said Richard Wiles of the Environmental Working Group, which plans a legal challenge if FDA doesn't change its position.
He said a single 6-ounce can of albacore a week could put many women, depending on their size, over the government's safe mercury limit: one-tenth of a microgram per kilogram of body weight per day.
Mercury accumulates in fish over time; canned light tuna comes from small fish, albacore and steaks from larger ones.
Eleven states already tell pregnant women to limit consumption of canned tuna, and Rhode Island last summer told them to avoid albacore, said Michael Bender of the Mercury Policy Project.
Nobody actually knows how much tuna or other mercury-containing fish pregnant women and young children eat today. But last year tuna slipped from the most-eaten seafood to No. 2, replaced by shrimp.
Even though albacore has more mercury than light tuna, it still contains levels well below safe limits, stressed Dave Burney of the U.S. Tuna Foundation.
"Albacore tuna happens to have more omega-3 in it than any other fish," he said. "Any advice for women to not eat fish is the wrong message to send."
But Consumers Union is urging the FDA to rewrite its advice and tell consumers what the lowest-mercury options are _ such as crab, catfish, flounder, salmon and shrimp _ instead of focusing just on what to avoid.
"The message should be, 'Eat more fish for your health while minimizing your mercury intake,'" said Consumers Union scientist Edward Groth.
Also, parents need to know how much fish is safe for young children, he said. FDA's planned advice just says they should eat less than adults.
Tuna aside, FDA's draft advice does warn that fish caught from local lakes and rivers often contains more mercury than commercial fish _ so heed local warnings on which freshwater fish to avoid. If there is no advice for your area, eat no more than 6 ounces of locally caught fish a week, the draft says.