BELTSVILLE, Md. -- The government should tell pregnant women to limit their consumption of tuna because of concern that eating lots of the fish could expose an unborn baby's developing brain to possibly harmful mercury levels, scientific advisers recommended Thursday.
It is not clear how much tuna women should eat, the Food and Drug Administration panel said -- perhaps two six-ounce cans a week if that is the only fish they eat, or a single can if other seafood, which also can contain mercury, is on their diet.
The panel urged the Food and Drug Administration to quickly study what proportion of the mercury in a woman's diet comes from tuna so more precise advice can be given. In the interim, extra care was suggested.
"Nobody wants to tell people to stop eating tuna fish," said the panel chairman, Sanford Miller of Virginia Tech University. "We're trying to balance the very positive virtues of fish, including tuna fish, with the harms. It's a very hard balance to make."
Industry representatives testified that few pregnant women eat enough fish, much less tuna, to absorb worrisome mercury levels. They believe the FDA's advice last year about avoiding certain fish and watching how much seafood they eat is sufficient, based on the available scientific research.
"We always believe it's appropriate for the FDA to look at as much evidence as possible," said Randi Thomas of the U.S. Tuna Foundation. "We will always support looking into this, doing the research and gathering the information."
Telling a pregnant woman not to eat her daily tuna sandwich might mean she goes for higher-fat bologna instead, which is not a great choice, said panelist Joseph Hotchkiss, a Cornell University food scientist.
FDA food safety chief Joseph Levitt could not say how quickly the agency would issue new consumer advice, but he said it was a priority.
Fish is very nutritious, with certain types containing high levels of heart-healthy fats, plus fats important for fetal brain development.
But some species also harbor different amounts of mercury, a toxic metal that contaminates seafood and is believed most harmful to the growing brains of fetuses and young children. Typically, the largest fish contain the most mercury.
About 8% of U.S. women of childbearing age have enough mercury in their blood to be at risk. The National Academy of Sciences estimates that 60,000 newborns a year could be at risk of learning disabilities because of mercury their mothers absorbed during pregnancy.
So the FDA last year advised pregnant women and those who could become pregnant not to eat four types of fish: shark, swordfish, king mackerel and tilefish, also called golden or white snapper.
The agency said those women could safely eat up to 12 ounces a week of other cooked fish, including canned tuna, shellfish and smaller ocean fish.
But critics said tuna, the nation's most eaten seafood, also should be limited. Large tuna steaks contain somewhat less mercury than swordfish, and numerous consumer advocacy groups urge pregnant women not eat to eat those.
While canned tuna fish is made from smaller fish that typically contain even less mercury, consumer groups -- and some state governments -- also advise pregnant women to limit their consumption. Wisconsin, for example, recommends one meal a week of canned tuna and one meal of another fish, or two tuna meals if the women eat no other fish.
The FDA brought together its scientific advisers to decide if the agency erred and should issue more precautions.
Pregnant women would have to eat more than two cans of tuna a day for weeks to pass a very conservative safety threshold, FDA food scientist Michael Bolger told the panel.
Some advisers questioned his estimate, but ultimately they could not say what amount of tuna was safer.
The panel urged the FDA to quickly research some crucial questions -- such as much of a women's mercury exposure comes from eating tuna -- while also telling women to eat tuna in moderation, much like Wisconsin recommends.
That message is for young children, too, the committee said.
The FDA panel's advice is not as strict as guidance from some consumer advocates, but they called it a victory.
"The advisory committee says FDA can't leave consumers in the dark about mercury in their favorite fish, tuna," said Caroline Smith DeWaal of the Center for Science in the Public Interest.
The FDA deems fish safe if they contain less than 1 part per million of methylmercury. The four types on the list to avoid exceed that level.
The average commercial fish contains far less -- 0.12 parts per million. Canned tuna on average contains only slightly more than that, but amounts can vary to as much as 0.75 parts per million.
Regardless of what other fish might be added to warnings, some advisers said that as many as half of women do not know about the current mercury advice. The advisers urged the FDA to be more aggressive in getting the word out.
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