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 advisers said _ perhaps two 6-ounce cans a week if that is the only fish they eat, or a single can if other seafood, which can contain mercury, is in 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 Polytechnic Institute. "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.
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 percent 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 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.