The benefits of omega-3 fatty acids seem to outweigh possible harm from mercury.
In 2004, in an effort to reduce fetal neurotoxicity from mercury exposure, the U.S. government advised pregnant women to limit seafood intake to 340 g per week or less. However, seafood is an important source of omega-3 fatty acids that are essential to fetal neurodevelopment.
U.K. researchers reanalyzed data from a cohort study of 8946 pregnant women that began in 1991. (British and U.S. seafood mercury levels are similar.) Periodically during and after their pregnancies, the women provided information about their diet, education, and social circumstances and their children’s development. Each child underwent a standard intelligence test at age 8.
The data were adjusted for 28 potentially confounding variables, including birth outcomes, socioeconomic and lifestyle factors, and intake of 12 other food groups. Compared with children whose mothers’ seafood intake exceeded 340 g weekly in pregnancy, those whose mothers ate less seafood had significantly poorer outcomes on 9 of 23 neurodevelopmental measures, including various fine-motor, communication, and social development milestones and verbal IQ at 8 years.
Comment: Despite the possibility of residual confounding, high seafood intake in pregnancy appears to benefit, not harm, fetal and childhood neurodevelopment. Seemingly, the benefits of essential omega-3 fatty acids in seafood outweigh any harm from trace amounts of mercury, and the 2004 recommendations, which were based on less-than-conclusive evidence, should be reassessed.
— Bruce Soloway, MD
Published in Journal Watch General Medicine February 27, 2007
Hibbeln JR et al. Maternal seafood consumption in pregnancy and neurodevelopmental outcomes in childhood (ALSPAC study): An observational cohort study. Lancet 2007 Feb 17; 369:578-85.