Study suggests fish consumption during pregnancy can affect ADHD tendency

Pregnant women’s fish intake may have an influence on their children’s proclivity toward Attention Deficit Hyperactivity Disorder (ADHD) in more ways than one, according to a study released this month by the Archives of Pediatrics & Adolescent Medicine. In their research, study authors recruited about 600 pregnant women in New Bedford, Mass. Between 1993 and 1998. About 400 of the mothers agreed to provide a hair sample which was tested for mercury levels, and about 500 of the mothers completed a survey which asked questions about their fish consumption. Eight years later, researchers checked on participants’ children to find what, if any, ADHD-related behaviors were present, using testing as well as teachers’ reports.

The average mercury level present in the study’s mothers was .45 microgram per gram. However, research found mothers whose mercury levels were 1 microgram or higher were much likelier to have children suffering from ADHD behavior—between 40 and 70 percent compared to the national average of 10 percent.

The finding correlates with the United States Environmental Protection Agency and the Food and Drug Administration’s recommendations that pregnant woman and nursing mothers limit fish consumption to 12 ounces, or about two servings, per week. It also reiterates the conclusion of another recent study which found Inuit children in Quebec who were exposed to higher prenatal levels of mercury—tested in samples of umbilical-cord blood—were more likely to exhibit ADHD symptoms.

Still, expectant mothers should not avoid eating fish during pregnancy. In what could be considered conflicting evidence on the surface, the new study also found women who reported eating more than the federally-recommended two servings of fish each week during pregnancy were up to 60 percent less likely to have a child who exhibited signs of ADHD. Their children were not only more attentive in class, but were able to solve computer test problems more quickly.

Fish are a known source of omega-3 fatty acids, vital for healthy brain development. But the two opposing statistics left researchers wondering how they correlated. Did the women who ate a lot of fish by coincidence eat types with low mercury content? Or were the women sticking to the two-serving recommendation eating fish with a higher content? Could the higher nutrition obtained from eating more fish counteract the effects of mercury? What was the catch?

Although the questions call for further examination on the topic, study author Susan A. Korrick, an associate physician at Brigham and Women’s Hospital in Boston, explained that a pregnant woman can reap the benefits of fish consumption by eating a lot of fish low in mercury. Likewise, she could also eat a low amount of fish high in mercury and her child could be more prone to ADHD.

Physician Bruce Lanphear, who studies brain function at Simon Fraser University in Vancouver, Canada, told WebMD the health benefits of fish consumption are often mistaken with concerns over mercury levels in fish. Without taking both into account, you can underestimate the nutritional benefits of fish, or underestimate the harmful effects of mercury exposure.

Study author Sharon Sagiv of Boston University advises pregnant women to eat fish species known for low mercury content. According to the Natural Resources Defense Council’s guide to mercury in fish, smaller, oily species such as catfish, mullet, trout, sardines, sole, tilapia and wild-caught salmon are prime choices for low mercury. In general, large species that tend to dwell in deep waters, such as tuna, swordfish, shark and mackerel, will have higher mercury content.

References:
Sagiv, Sharon, et al. “Prenatal Exposure to Mercury and Fish Consumption During Pregnancy and Attention-Deficit-Hyperactivity Disorder-Related Behavior in Children.” Oct. 2012. Archives of Pediatrics & Adolescent Medicine.http://archpedi.jamanetwork.com/article.aspx?articleid=1377487#COMMENT

Goodman, Brenda. “Limit Fish While Pregnant? Study Questions Advice.” Oct. 8, 2012. WebMD. <http://www.webmd.com/add-adhd/news/20121008/limit-fish-while-pregnant-study-questions-advice

“Consumer Guide to Mercury in Fish.” Natural Resources Defense Council. <http://www.nrdc.org/health/effects/mercury/guide.asp
Castillo, Michelle. “Study: Mercury increases, fish decreases ADHD risk in kids.” Oct. 9, 2012. CBS News. <http://www.cbsnews.com/8301-204_162-57528769/study-mercury-increases-fish-decreases-adhd-risk-in-kids/

Gardner, Amanda. “Mercury Exposure in Womb Linked to ADHD Symptoms.” Oct. 8, 2012. Health Magazine. <http://news.health.com/2012/10/08/mercury-exposure-adhd/