New research has linked low-level mercury exposure in pregnant women to an increased risk of attention deficit hyperactivity disorder (ADHD) in their children.
But the same research also found that eating fish during pregnancy can help reduce the risk of ADHD-related behaviors in children.
The scientists who led the study, Susan Korrick, M.D., M.P.H., of Brigham and Women’s Hospital, and Sharon Sagiv, Ph.D., M.P.H., of Boston University School of Public Health, said this “duality” is possible because many types of fish have low levels of mercury, so it is possible for a pregnant woman to eat nutritionally beneficial fish without being exposed to much mercury.
“These findings underscore the difficulties pregnant women face when trying to balance the nutritional benefits of fish intake with the potential detriments of low-level mercury exposure,” said Korrick.
“Women need to know that nutrients in fish are good for the brain of a developing fetus, but women need to be aware that high mercury levels in some fish pose a risk,” added Sagiv.
This study involved approximately 400 children born in New Bedford, Mass., between 1993 and 1998. Shortly after their mothers gave birth, researchers collected hair samples from the mothers and analyzed them for mercury.
They also gave the mothers a questionnaire to determine their fish consumption during pregnancy. Eight years later, researchers followed up with the children and administered standardized tests to determine behaviors related to ADHD.
Researchers found an increased risk of childhood ADHD-related behaviors with increasing maternal hair mercury levels.
These mercury levels were lower than levels shown to be potentially hazardous in previous studies, the researchers noted.
Additionally, researchers found a reduced risk of ADHD-related behaviors in children whose mothers reported eating more than two servings of fish per week, which is a higher number of servings than is currently recommended by the United States Food and Drug Administration and Environmental Protection Agency.
The study did not examine what types of fish are best for a pregnant woman to eat, but previous studies have shown women should avoid fish that are high in mercury, such as shark, swordfish, king mackerel and fresh tuna.
Fish that are low in mercury, such as flounder, haddock, and salmon, are safer to eat and good sources of nutrition, the researchers concluded.
The study was published in the online version of the Archives of Pediatrics & Adolescent Medicine.
Source: Brigham and Women’s Hospital