Pregnant women can eat moderate amounts of fish without worry. That’s the key conclusion of a new analysis of studies that found exposure to low levels of mercury on the developing brain — specifically by women consuming fish during pregnancy — does not raise the risk of autism.
"This study shows no evidence of a correlation between low level mercury exposure and autism spectrum-like behaviors among children whose mothers ate, on average, up to 12 meals of fish each week during pregnancy," said Edwin van Wijngaarden, an associate professor in the University of Rochester Medical Center's Department of Public Health Sciences who led the study.
"These findings contribute to the growing body of literature that suggest that exposure to the chemical does not play an important role in the onset of these behaviors."
Fish are high in beneficial nutrients such as, selenium, vitamin E, lean protein, and omega-3 fatty acids, essential to brain development. But some studies have suggested prenatal exposure to high levels of mercury can lead to developmental problems.
The U.S. Food and Drug Administration recommends that pregnant women and children limit their consumption of certain kinds of fish known to have higher mercury levels. Fish with the highest levels of mercury contamination include shark, swordfish, king mackerel, and tilefish.
But the FDA says it’s healthy for pregnant women and children to consume eight ounces (two average meals) per week of fish and shellfish that are lower in mercury — such as shrimp, canned light tuna, salmon, Pollock, and catfish — and check local advisories about the safety of fish caught by family and friends in local lakes, rivers, and coastal areas.
For the new study, researchers focused on the people living in the Republic of Seychelles — a population of 87,000 people spread across a series of islands in the Indian Ocean who consume fish at a rate 10 times greater than the populations of the U.S. and Europe.
The study involved 1,784 children, adolescents, and young adults and their mothers. The researchers determined the level of prenatal mercury exposure by analyzing hair samples that had been collected from the mothers around the time of birth. They then used questionnaires to determine whether or not the study participants were exhibiting autism spectrum-like behaviors.
When the mercury levels of the mothers were then matched with the test scores of their children, the researchers found that there was no correlation between prenatal exposure and evidence of autism-spectrum-like behaviors.
"NIEHS has been a major supporter of research looking into the human health risks associated with mercury exposure," said Cindy Lawler, acting branch chief at the National Institute of Environmental Health Sciences, part of National Institutes of Health.
"The studies conducted in the Seychelles Islands have provided a unique opportunity to better understand the relationship between environmental factors, such as mercury, and the role they may play in the development of diseases like autism. Although more research is needed, this study does present some good news for parents."
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