WASHINGTON (Reuters) - Children of mothers who ate more fish and other seafood while pregnant are smarter and have better developmental skills than kids of women who ate less or none, researchers said on Thursday in findings they called surprising.
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The study, sure to be controversial, sought to assess whether it is wise, as some experts and the U.S. government have recommended, for pregnant women to limit their seafood intake to avoid mercury, a toxin that can harm the nervous system of developing foetuses.
Dr. Joseph Hibbeln, a U.S. National Institutes of Health researcher who led the study in The Lancet medical journal, said seafood is a key source of omega-3 fatty acids, important for fetal brain development.
The researchers said limiting pregnant women's weekly intake to 340 grams (12 ounces) of fish and seafood, as advised by the U.S. government, did not protect their children from developmental problems. Women who avoid seafood, they said, may actually be harming their babies by depriving them of essential nutrients needed for the developing fetal brain.
"It was very surprising," Hibbeln said in a telephone interview. "We did not expect such clear-cut results of the harm of low seafood consumption."
The study looked at the children of more than 8,000 British women tracked by the University of Bristol to determine how kids fared if their mothers ate more than 12 ounces -- about two average meals.
These children, compared to those whose mothers ate lesser amounts, were more advanced in developmental tests measuring fine motor, communication and social skills as toddlers, behaved better at age 7, and earned higher verbal IQ scores at age 8, the study found.
The differences were striking when looking at kids whose mothers ate no seafood. They were 48 percent more likely to have a relatively low verbal IQ score at age 8 compared to children whose mothers ate the higher amount of seafood.
The Environmental Working Group, which calls the U.S. recommendations too lenient, said the study highlighted the need for governments to take actions to keep pollutants out of seafood, like cracking down on coal-burning power plants.
"The study reinforces the importance of keeping our seafood supply clean, making sure it's not overly contaminated with mercury and other chemicals that could actually harm brain development," said Jane Houlihan, the group's vice president for research.
Mercury can build up in fish living in waters contaminated with it due to industrial pollution. Mercury can be particularly bad for foetuses and children because it can cause neurological and developmental problems.
In 2004 the U.S. Environmental Protection Agency and Food and Drug Administration advised pregnant women and young children to eat no more than 12 ounces per week of light tuna and other seafood lower in mercury.
The agencies recommended they eat none of some fish with high mercury levels -- shark, swordfish, king mackerel and tilefish -- and no more than 6 ounces (170 grams) a week of albacore tuna because of mercury.
"When you look at the net benefits of the nutrients in seafood and the net risks in seafood, it appears that the advisory inadvertently causes the harm that it was intended to prevent," Hibbeln said.
In a commentary in Lancet, Dr. Gary Myers and Philip Davidson of the University of Rochester Medical Centre in New York wrote, "These results highlight the importance of including fish in the maternal diet during pregnancy and lend support to the popular opinion that fish is brain food."
The full abstract of the study can be found at the PubMed website.