Women who eat seafood while pregnant may be boosting their children’s IQ in the process, according to new research published Friday in The Lancet.
The results of the study were surprising, say the authors, and contradict American and British recommendations that pregnant women should limit seafood and fish consumption to avoid potentially high levels of mercury. The study relied on mothers’ observations of their children’s development and their reports of their food intake while pregnant.
Mercury is found in small concentrations in fish and seafood, but can accumulate in the body. High amounts of the metal can damage the human nervous system, particularly those in developing fetuses. On the other hand, seafood — including fish — is also a major source of omega-3 fatty acids, essential to brain development.
While experts believe further research is necessary to confirm these conclusions, the study’s failure to find evidence of increased harm from eating fish is significant. Because seafood contain both nutrients and toxins, it remains a dilemma for regulatory authorities what kinds of recommendations should exist for pregnant women.
The study, led by Dr. Joseph Hibbeln of the United States’ National Institutes of Health, tracked the eating habits of 11,875 pregnant women in Bristol, Britain.
At 32 weeks into their pregnancy, the women were asked to fill in a seafood consumption questionnaire. They were subsequently sent questionnaires four times during their pregnancy, and then up to eight years after the birth of their child. Researchers examined issues including the children’s social and communication skills, their hand-eye coordination, and their IQ levels. As with any study based on self-reporting methods, however, the results cannot be considered entirely definitive.
The study was primarily funded by Britain’s Medical Research Council, the Wellcome Trust, the University of Bristol, and the British government.
Hibbeln and his colleagues concluded that women who ate more than 340 grams per week of fish or seafood — the equivalent of two or three servings a week — had smarter children with better developmental skills. Children whose mothers ate no seafood were 48 percent more likely to have a low verbal IQ score, compared to children whose mothers ate high amounts of seafood.
“These results highlight the importance of including fish in the maternal diet and lend support to the popular opinion that fish is brain food,” wrote Dr. Gary Myers and Dr. Philip Davidson of the University of Rochester Medical Center, in an accompanying commentary. Myers and Davidson were not connected to the study.
Eating even more than three portions of fish or seafood a week could be beneficial, Hibbeln suggests. “Advice that limits seafood consumption might reduce the intake of nutrients necessary for optimum neurological development,” he and his colleagues wrote.
The researchers said limiting pregnant women’s weekly intake to 12 ounces (340 grams) 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 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.
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.