Environment Food and Nutrition Health — 10 October 2012

Eating fish high in mercury during pregnancy may increase a woman’s risk of having a child with attention deficit hyperactivity disorder (ADHD),  according to a new study published in the Archives of Pediatrics and Adolescent Medicine.

The study looked at the births of nearly 600 children over a five year period. After studying hair samples of the mothers for prenatal mercury exposure and analyzing their fish intake during pregnancy, researchers concluded that a child’s risk of ADHD increased by 40 to 70 percent when their mothers consumed fish with high levels of mercury.

However, they also found that women who ate more than two servings of fish a week low in mercury had a 60 percent reduced risk of having children with ADHD-related behavior.

Currently, the Food and Drug administration recommends that pregnant women limit their intake of fish to no more than two six-ounce servings each week.

“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 study author Susan Korrick, assistant professor of medicine at Brigham and Women’s Hospital, Boston.

“It’s possible to eat fish low in mercury and high in nutritional value, and it’s possible to eat fish high in mercury and low in nutritional value,” said Korrick. “What really matters is the kind of fish you’re eating.”

While fish is a primary source of dietary mercury, it is also a good source of omega-3 fatty acids, healthy fats that are essential to brain development.

In an editorial accompanying the study, Bruce Lanphear, a professor of health sciences at Simon Fraser University in Vancouver, wrote that the findings add to a growing body of evidence that show that exposure to environmental toxins, including tobacco and lead, can lead to ADHD.

“This study and a flurry of new evidence linking environmental contaminants with ADHD reinforce the urgency of revising the regulatory framework for environmental contaminants and toxicants,” said Lanphear, who called for a national scientific advisory panel to study the issue.

The study did not analyze which fish would most likely be contaminated with mercury, but previous research has shown that shark, swordfish, king mackerel and fresh tuna to have high mercury levels, while salmon, shrimp and haddock had lower levels.

According to Lanphear, it’s unclear exactly how mercury can lead to ADHD-related behavior, although research suggests that the behavioral disorder results from an imbalance or a deficiency of the brain chemical dopamine. Mercury may alter dopamine levels or change dopamine receptors.

Despite the unanswered questions, Lanphear said the study has many important implications and now is the time to act on them.

“In the long term, we have to really find ways to fight contamination levels in fish so years from now we don’t have to give this advice,” he said.

ADHD is a neurobehavioral disorder characterized by inattention, hyperactivity and impulsiveness. Although it’s most often associated with children, nearly 5% of American adults have ADHD.

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Richard Lenti

Richard Lenti has worked as a news writer for the last 20 years at various television stations in Los Angeles. He is a Golden Mike winner and a graduate of California State University, Fresno. With roots in print journalism, Richard is excited to be “published” once again; having people read his work as opposed to having it read to them. As a freelance writer his work has appeared in the Easy Reader, L.A. Jazz Scene, Irrigation and Green Industry, and the KCAL 9 Online website.

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