The levels of mercury in a pregnant woman's bloodstream has been linked to a higher risk of her child being diagnosed with attention deficit hyperactivity disorder (ADHD) by a new study conducted by researchers at Boston's Brigham and Women's Hospital and the Harvard School of Public Health. The Boston Globe reports that children whose mothers tested high for mercury were 40-70 percent more likely to exhibit ADHD symptoms by age eight:
On the flip side, those children whose mothers consumed the most fish while pregnant were the least likely to exhibit fidgety, distracted, and impulsive behaviors in class, according to the study of 604 children published Monday in the Archives of Pediatrics and Adolescent Medicine.
At first blush, this finding appears contradictory because most of the mercury we consume comes from fish. "It seems a little paradoxical," said study co-author Dr. Susan Korrick, an assistant professor of medicine at Brigham and Women's. "But fish consumption doesn't necessarily correlate with mercury levels since you could eat a high amount of fish that are low in mercury."
Fatty kinds of fish such as salmon, tuna, and sardines have higher levels of omega-3 fatty acids, which are thought to be crucial for cognitive function. All types of fish have a host of nutrients such as vitamin D, B-12, and iodine, which could play a role in brain development as well.
While government agencies have advised pregnant women to limit their fish intake to no more than two six-ounce servings a week, Korrick said they might want to aim for three or four servings of low-mercury fish such as salmon, canned light tuna, haddock, cod, and shrimp. (Albacore tuna has more mercury, so consumption should be limited to six ounces a week.)
The key is for pregnant women to avoid fish known to have high mercury levels, including swordfish, shark, tilefish, and king mackerel, Korrick added.
Image: Salmon, via Shutterstock