Of fish and brain health Moms-to-be who eat a diet rich in the right fish may pass along benefits to their children People who eat sharks, like the mako shown here, face the risk of ingesting high levels of mercury, a toxic metal linked to health problems. Credit: NOAA You may have heard that “you are what you eat.” But in the nine months before a baby’s born, its mother’s diet can also make a big difference. And whether that mom ate fish could play an important role in her baby’s brain health, a new study reports. In the study, children born to women who ate fish during pregnancy were less likely to have behaviors like inattention and hyperactivity, which are associated with a syndrome known as attention- deficit/hyperactivity disorder, or ADHD. About 1 in every 12 children in the United States is diagnosed with ADHD. Fish often gets a bad rap because some, like shark and swordfish, contain high levels of mercury. This toxic metal is connected to many health problems. Pregnant women are advised to avoid eating fish that have picked up high levels of mercury from their environment. It is possible, however, to eat a fish-rich diet without accumulating a lot of mercury, explains Susan Korrick, an epidemiologist at the Brigham and Women’s Hospital in Boston. “It really depends on the type of fish that you’re eating,” she told Science News. Korrick worked on the new study of diet and behavior. Epidemiologists like Korrick study diseases and other influences on the health of the general population. Some of the women who participated in her team’s study ate fish more than two times per week but accumulated only tiny traces of mercury. Korrick and her coworkers studied more than 500 women who gave birth during the 1990s in New Bedford, Mass. Shortly after giving birth, these women completed a questionnaire about their diets. More than 400 of them also allowed the scientists to use hair samples to test for mercury. About eight years later, Korrick’s team evaluated the behaviors of these women’s children. Some of the kids had ADHD. Many others didn’t, although they did exhibit some behaviors that researchers have linked with ADHD. Korrick’s team found that overall, children whose moms had eaten fish were less likely to have ADHD or related symptoms. But this was true only if their mom’s hair also contained little mercury (less than 1 microgram per gram of hair). When a mom’s hair concentrations of mercury were higher, a child’s risk of ADHD-related behaviors rose. And for these kids, a mom’s fishy diet during pregnancy didn’t protect them. Moreover, in some types of tests, especially those measuring a child’s ability to pay attention, elevated exposure to mercury in the womb seemed to cause bigger problems in boys than in girls. A second, new study found a link between high levels of mercury in newborns and increased risk of being diagnosed with ADHD by age 11. Other studies have also linked a child’s early exposure to other pollutants, such as lead (a heavy metal), with an increased risk of developing ADHD-related traits. Lots of foods may contain traces of toxic pollutants. The new studies show that keeping levels of those pollutants low is especially important during pregnancy, when a baby’s brain is developing. Power Words pollutant An unintended or discarded — and sometimes harmful — substance in the environment. mercury The chemical element with the atomic number 80. It is a heavy, silvery-white metal that is liquid at room temperature. lead A heavy, bluish-gray, soft metal that can harm the nervous system, including IQ. ADHD, or attention-deficit/hyperactivity disorder Any of a range of behavioral disorders developing primarily in children and including such symptoms as poor concentration, hyperactivity and impulsivity.