Researchers Create New Model to Assess Risks and Benefits of Eating Fish During Pregnancy

Researchers have developed a new model to help guide recommendations and improve evidence-based advice on the risks and benefits of fish consumption, particularly during pregnancy.

In a study published in The American Journal of Epidemiology, scientists from Brigham and Women’s Hospital, Harvard T.H. Chan School of Public Health, University of Rochester Medical Center, and Cornell University introduced a framework that considers the average mercury content in fish. This model helps balance the harmful effects of mercury against the nutritional benefits of fish, providing clearer guidance on safe fish consumption.

Methylmercury (MeHg) exposure can harm brain development. However, fish also contain many nutrients that are good for brain development, like polyunsaturated fatty acids, selenium, iodine, and vitamin D. Many studies measure mercury exposure by looking at how much mercury has built up in hair. But using hair samples alone makes it hard to separate the harmful effects of mercury from the benefits of eating fish. For example, eating a lot of fish with low mercury levels or a small amount of fish with high mercury levels can show the same mercury level in hair samples, but the health risks are different.

In the study, researchers examined the relationship between fish consumption—categorized into low, medium, and high average mercury levels—and neurodevelopment in children. They assessed neurodevelopment using tests for IQ, language, memory, and attention.

The findings showed that children whose mothers consumed more fish with low mercury levels had better neurodevelopmental outcomes. Conversely, children whose mothers ate fish with high mercury levels had poorer neurodevelopmental outcomes.

“For patients who are seeking guidance about fish consumption, public advisories can be confusing and lead to decreased fish intake. 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. People need to think about what kind of fish they are consuming rather than simply cutting down on fish intake entirely. Our goal is for our study to help facilitate better estimation of the risk-benefit trade-offs of fish consumption, a key component of many healthy diets,” said lead author Sally Thurston, of the University of Rochester Medical Center.

Reference: Sally W Thurston, David Ruppert, Susan A Korrick, A Novel Approach to Assessing the Joint Effects of Mercury and Fish Consumption on Neurodevelopment in the New Bedford Cohort, American Journal of Epidemiology, 2024;, kwae149, https://doi.org/10.1093/aje/kwae149