Researchers Create New Model for Fish Consumption in Expectant Mothers

A study published in the American Journal of Epidemiology demonstrates research that might change the understanding and provide clearer guidance on the consumption of fish for women who are pregnant. Previously, the FDA recommended that expectant mothers should limit fish consumption because of the amount of methylmercury (MeHg), which is a known neurotoxicant; however, fish also contain essential nutrients that help brain development, such as polyunsaturated fatty acids, selenium, iodine, and vitamin D.¹

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“For patients who are seeking guidance about fish consumption, public advisories can be confusing and lead to decreased fish intake,” said senior author Susan Korrick, MD, Brigham’s Channing Division of Network Medicine and Division of Pulmonary and Critical Care Medicine, in a news release.²

The study enrolled a cohort of pregnant mothers and assessed the joint association of prenatal MeHg exposure and fish intake among mothers who consumed fish with the neurodevelopment of 361 children 8 years of age who were born to these mothers. Neurodevelopment assessments consisted of standardized tests of IQ, language, memory, and attention, with covariate-adjusted regression assessing the association of maternal fish consumption stratified by tertiles of estimated average fish Hg, with neurodevelopment.^1,3

“We propose an alternative modeling approach to address limitations of previous models and to contribute thereby to improved evidence-based advice on the risks and benefits of fish consumption,” said the authors in another press release. “In fish-eating populations, this can be addressed by separating mercury exposure into fish intake and average mercury content of the consumed fish.”¹

The researchers measured mercury exposure during the third trimester through hair samples collected from the mothers following birth. According to the investigators, this method alone cannot properly assess maternal mercury exposure in women who frequently consumed low-mercury fish compared to those who consumed a smaller quantity of high-mercury fish. To accommodate for this, the investigators created a model that included the estimates of mercury exposure per servicing of fish, which was conducted through food questionnaires and reports from the mothers that included the type and frequency of fish and shellfish consumed during pregnancy. From there, the authors were able to estimate mercury levels by the type of fish, and when combined with the information on the mothers’ diets, they were able to develop a more precise, detailed method to estimate joint associations of pregnancy fish intake and fish mercury levels of the neurodevelopment of their children.^1,3

According to the findings, the relation between pregnancy fish consumption and the neurodevelopment varied depending on the estimated mercury levels in the fish. For example, associations were found to be beneficial for those in the lowest average fish mercury tertile; however, the higher average mercury present in the fish was associated with more detrimental neurodevelopmental outcomes.^1,3

“Our study finds that eating more fish was generally beneficial for neurodevelopment when pregnant individuals consumed fish containing low levels of mercury but detrimental when individuals consumed fish with the highest average mercury levels. It’s important for people to think about what kind of fish they are consuming rather than simply cutting down on fish intake entirely,” said lead author Sally Thurston, PhD, University of Rochester Medical Center, in a press release.²

The investigators note that potential limitation of the study includes inaccuracies of both self-reported survey measures of participants’ diets as well as estimates of mercury in fish, and the exclusion of variation in the beneficial nutrients present in the consumed fish. Additionally, the authors note that the study’s population was enrolled from the New Bedford area.³

“Given methodologic limitations to previous 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 tradeoffs of fish consumption, a key component of many healthy diets,” said the authors in a news release.¹

References

1. University of Rochester Medical Center. New model could help provide expectant mothers a clearer path to safe fish consumption. News release. June 28, 2024. Accessed July 3, 2024. https://www.eurekalert.org/news-releases/1049586

2. Brigham and Women’s Hospital—Mass General Brigham. Researchers Develop New and Improved Model to Weigh the Risks and Benefits of Fish Consumption. News release. June 28, 2024. Accessed July 3, 2024. Email.

3. Thurston SW, Ruppert D, Korrick SA. A Novel Approach to Assessing the Joint Effects of Mercury and Fish Consumption on Neurodevelopment in the New Bedford Cohort. Am J Epidemiol. Published online June 28, 2024. doi:10.1093/aje/kwae149