Researchers develop new, improved model to assess risks and benefits of fish consumption

A new model developed by researchers could help inform guidelines and improve evidence-based advice on the risks and benefits of fish consumption, particularly during pregnancy.

In an article published in The American Journal of EpidemiologyResearchers from Brigham and Women’s Hospital, a founding member of Mass General Brigham, Harvard T.H. Chan School of Public Health, the University of Rochester Medical Center and Cornell University present a new framework that considers the estimated average mercury content of fish consumed, helping to weigh the harmful effects of mercury against the potential benefits of nutrients found in fish.

Applying this approach to a fish-eating population in Massachusetts, the team found that, in general, consuming increasing amounts of low-mercury fish during pregnancy was beneficial, while consuming more high-mercury fish was harmful to neurodevelopment.

“For patients seeking advice about fish consumption, public advisories can be confusing and lead to a reduction in fish consumption,” said lead author Susan Korrick, MD, of the Division of Network Medicine. and the Division of Pulmonary and Critical Care Medicine at Brigham’s Channing. Korrick is also a member of the Harvard Chan-NIEHS Center for Environmental Health.

“Our study found that eating more fish was generally beneficial for neurodevelopment when pregnant people consumed fish with low levels of mercury, but detrimental when individuals consumed fish with the highest average mercury levels. It is important for people to think about the type of fish they eat rather than simply reducing fish consumption altogether,” said lead author Sally Thurston, Ph.D., of the University of Rochester Medical Center.

Exposure to methylmercury (MeHg) can lead to neurodevelopmental toxicity. However, many nutrients in fish are beneficial for neurodevelopment, including polyunsaturated fatty acids, selenium, iodine and vitamin D.

Many studies examining the relationship between mercury exposure and health effects measure mercury based on its accumulation in hair.

However, relying solely on hair samples makes it impossible to distinguish between the potentially harmful effects of mercury and the beneficial effects of fish consumption. For example, eating a lot of fish with low levels of mercury or very little fish with high amounts of mercury could result in the same level of mercury in a hair sample but carry different potential health risks.

The results of analyses using common statistical approaches on this question can be difficult to interpret. To address these limitations, the researchers proposed a new model in which they took into account the estimated average mercury content of the fish consumed.

The team looked at data from participants in the New Bedford Cohort (NBC), a study that followed 788 children of mothers living near the New Bedford Harbor Superfund site in Massachusetts.

In addition to studying hair samples, the team used survey data from a food frequency questionnaire that mothers completed about 10 days after giving birth. Participants provided information about the different types of fish they ate during pregnancy.

The researchers studied the relationship between fish consumption (low, medium, and high mercury intake) and the neurodevelopment of the children in the cohort. The team measured neurodevelopment using tests of IQ, language, memory, and attention.

For children whose mothers consumed more fish in the lowest mercury category, fish consumption was positively (beneficially) associated with neurodevelopmental outcomes; Conversely, for children whose mothers consumed fish containing the highest mercury levels, the association between fish consumption and neurodevelopmental outcomes was negative (detrimental).

The authors note several limitations of the study, including the fact that estimates of mercury content in fish as well as dietary survey measurements are imperfect. The study population included only participants from the New Bedford area and was only interested in neurodevelopmental outcomes. The study also did not account for variation in beneficial nutrients in the fish consumed, such as the content of polyunsaturated fatty acids or selenium.

“Our goal is that our study will facilitate better estimation of the risk-benefit trade-offs of fish consumption, a key component of many healthy diets,” said lead author Susan Korrick, MD, of the Channing Division of Brigham of network medicine and the division of Pulmonary and Intensive Care Medicine.

The team hopes that future work will expand on this modeling approach, taking into account both the average mercury content and the nutritional content of fish.

The authors are in the process of applying this model to other large studies of maternal fish consumption, including the Seychelles Child Development Study, in which Thurston is participating as an investigator.