The benefits of eating fish may do more than just offset the risks of mercury exposure to unborn babies. Research shows that nutrients in fish may actually shield the brain from the potentially toxic effects of the chemical.
The findings are based on a study that spans three decades. The results show that high levels of fish consumption by pregnant mothers in the Seychelles—an average of 12 meals per week—did not result in developmental problems in their children.
Researchers have previously equated this phenomenon to a kind of biological horse race, with the developmental benefits of nutrients in fish outpacing the possible harmful effects of mercury also found in fish.
However, the new research, published in the American Journal of Clinical Nutrition, indicates that this relation is far more complex. Compounds present in fish, specifically polyunsaturated fatty acids (PUFA), may also actively counteract the damage that mercury causes in the brain.
“These findings show no overall association between prenatal exposure to mercury through fish consumption and neurodevelopmental outcomes,” says co-author Edwin van Wijngaarden, associate professor of public health sciences at University of Rochester.
“It is also becoming increasingly clear that the benefits of fish consumption may outweigh any potentially adverse effects of mercury.”
“This research provided us the opportunity to study the role of polyunsaturated fatty acids on development and their potential to augment or counteract the toxic properties of mercury,” says lead author Sean Strain, professor of human nutrition at Ulster University in Northern Ireland.
“The findings indicate that the type of fatty acids a mother consumes before and during pregnancy may make a difference in terms of their child’s future neurological development.”
Benefits Versus Risks
The new study comes as the U.S. Food and Drug Administration (FDA) and international agencies are in the process of revisiting fish consumption advisories to better reflect the health benefits of nutrients found in fish.
The FDA’s current guidance—which recommends that pregnant women limit their consumption of certain fish to twice a week—was established because of the known risk of high-level mercury exposure on childhood development.
Mercury is found in the environment as a result of both natural and human (for example, coal plant emissions) activity. Much of it ends up being deposited in the world’s oceans and, as a result, fish harbor the chemical in very small amounts.
This has given rise to concerns that the cumulative impact of prenatal exposure to mercury through fish consumption may have negative health outcomes, despite the fact that a link between low-level exposure and developmental consequences in children has never been definitively established.
At the same time, fish are rich in a host of beneficial nutrients, including fatty acids, which are essential to brain development, leading to a long-standing exchange among scientists, environmentalists, and policymakers over the risk versus benefit of fish consumption.
The debate has significant consequences for global health, as billions of people across the world rely on fish as their primary source of protein.
Mothers in Seychelles
The National Institute of Environmental Health Sciences and the Government of Seychelles provided funding for the study.
The Seychelles Child Development Study—a partnership between the University of Rochester, Ulster University, and the Republic of Seychelles Ministry of Health and Ministry of Education—is one of the longest and largest population studies of its kind.
The Seychelles, a cluster of islands in the Indian Ocean, has proven to be the ideal location to examine the potential health impact of persistent low-level mercury exposure. The nation’s 89,000 residents consume fish at a rate 10 times greater than the populations of the United States and Europe.
The new study followed more than 1,500 mothers and their children.
