Initial research suggests that pregnant women who eat lots of fish – especially tuna, swordfish and other fish with high mercury levels are more likely to have children with ADHD. Researchers from the Boston University School of Public Health tracked 788 Massachusetts children between 1993 and 1998. Then they had the children’s mothers keep food diaries while they were pregnant so they could see how much fish the women ate. They took hair samples from them after they gave birth so they could test their mercury levels.

Eight years later, they asked the children’s teachers if the kids exhibited ADHD-like symptoms, such as hyperactivity, impulsiveness and inattentiveness. The researchers concluded that the women who had the most mercury in their hair were 60% more likely to have a child who exhibited ADHD-like behavior.