A new study suggests that exposure to mercury during pregnancy may increase the risk for attention deficit hyperactivity disorder (ADHD), while eating fish may reduce this risk.
Mercury is a neurotoxin, meaning it affects the nervous system. For fetuses, infants and children, the primary health effects of mercury are on nerve development. Even low levels of mercury exposure, such as may be the result of a mother's consumption of methylmercury in dietary sources (such as fish), may negatively affect the brain and nervous system. Impacts on memory, attention, language and other skills have been found in children exposed to moderate levels in the womb.
Oils from salmon, trout, tuna, herring, sardine, mackerel, eggs and some chicken contain omega-3 fatty acids that are needed to build brain tissue. Intake of omega-3 fatty acids during pregnancy may provide nutrition for proper brain and retina development of the fetus. However, fish absorb methylmercury from water as it passes over their gills and as they feed on aquatic organisms. Larger predator fish, such as swordfish and tuna, are exposed to higher levels of methylmercury from their prey.
In a new study, researchers assessed the potential relationships between prenatal mercury exposure and fish consumption with ADHD in children using hair mercury measures from 421 mothers and reports of fish consumption during pregnancy from 515 mothers. A teacher rating scale and other testing methods were used to identify ADHD-related behaviors in eight year-old children.
The researchers found that mercury exposure was linked to inattentive and hyperactive behaviors in children. Maternal hair mercury levels of one microgram per gram or greater were associated with a 40 percent increased risk of inattentive behavior in children and a 70 percent increased risk of hyperactive behavior. Conversely, regular fish consumption was linked to a decreased risk for ADHD-related behavior.
The authors noted that these findings highlight the need to balance the potential benefits and risks of eating fish during pregnancy. Further research is warranted.
For more information about pregnancy or ADHD risk factors, please visit Natural Standard's Medical Conditions Database.