Fish consumption during pregnancy is a complex scientific issue. On the one hand, fish is rich in nutrients essential for brain development, including polyunsaturated fatty acids, selenium, iodine and vitamin D. On the other hand, fish contains methylmercury, a known neurotoxin. This has led the U.S. Food and Drug Administration to recommend that expectant mothers limit their consumption, inadvertently causing many women to give up fish consumption altogether during pregnancy.
Fish consumption is an important route of exposure to methylmercury; However, efforts to understand the health risk posed by mercury are further complicated by the fact that the nutritional benefits of fish may modify or reduce the toxicity posed by mercury. A new study appearing in the American Journal of Epidemiology Based on data from a cohort of residents of a Massachusetts coastal community, a new framework has been created that could untangle these questions, reduce confusion, and produce clearer guidance on fish consumption for pregnant mothers.
“We propose an alternative modeling approach to address the limitations of previous models and thus contribute to improving evidence-based advice on the risks and benefits of fish consumption,” said the authors, who include Sally Thurston, PhD , of the University of Rochester Medical Center, Susan Korrick, MD, MPH, of the Harvard TH Chan School of Public Health and Brigham and Women’s Hospital, and David Ruppert, PhD, of Cornell University. “In populations that eat fish, this can be addressed by separating mercury exposure in fish intake and the average mercury content of the fish consumed.”
The new research comes from an analysis of data from the New Bedford Cohort, which was created to assess the health of children born to mothers residing near the New Bedford Harbor Superfund site in Massachusetts. The current study included 361 children from the cohort who were born between 1993 and 1998 and underwent neurodevelopmental assessments, including tests of IQ, language, memory and attention, at age eight.
Researchers were able to measure mercury exposure during the third trimester of pregnancy through hair samples collected from mothers after birth. While hair samples have been the traditional method for studying maternal mercury exposure, this approach alone cannot distinguish between mothers who frequently consumed low-mercury fish compared to those who consumed a lower amount of high-mercury fish.
To overcome this limitation, the researchers created a model that includes estimates of mercury exposure per serving of fish. This was possible because mothers in the cohort also completed a dietary questionnaire and reported the type and frequency of fish and seafood consumption during pregnancy. The authors calculated mean mercury levels by fish type, and by combining these with information on the mother’s diet, they were able to create a more precise and detailed method for estimating the joint associations between fish consumption during pregnancy and mercury levels in fish on neurodevelopment.
Using this model, the researchers found that the relationship between fish consumption during pregnancy and later neurological development varied depending on the estimated average levels of mercury in the fish. Specifically, consuming fish with low mercury content was beneficial, while consuming fish with higher levels of mercury was harmful.
“Given the methodological limitations of the above analyses, future work expanding our alternative modeling approach to account for both the average mercury and nutritional content of fish could facilitate better estimation of the risk-benefit trade-offs of fish consumption. a key component of many healthy diets,” the authors said.
The authors are in the process of applying this model to other large-scale studies of maternal fish consumption, including the Seychelles Child Development Study, in which Thurston is involved as an investigator.
He American Journal of Epidemiology The study was funded by the National Institute of Environmental Health Sciences.