When Pregnant Moms Eat Fish, Fewer Kids Have ADHD

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Fish—why do you have to be such a complicated food? Whether you like it baked, fried, or sashimi-style, a new study finds that children whose moms ate at least two servings of fish per week during pregnancy have a 60 percent lower risk of developing certain symptoms related to ADHD, like hyperactivity, impulsiveness and inattentiveness. But before you break out the lemon and tartar sauce, consider what else the study found: eating more fish—the type that contains higher levels of mercury—may be tied to a higher risk of children developing ADHD-like symptoms.

So what's on the menu tonight? Researchers from the Boston University School of Public Health followed 788 children who were born near the seaport city of New Bedford, Massachusetts, between 1993 and 1998. They used hair samples taken from the mothers right after delivery to test their mercury levels (because the body has a difficult time excreting methylmercury, it often ends up in the hair), and food diaries to see how much fish they ate. Then, once the children were about 8 years old, the researchers asked their teachers to evaluate the kids' behaviors to see how many exhibited ADHD-like symptoms.

After cross-checking their data, researchers found that having a mom with higher levels of mercury in her hair (1 microgram of mercury per gram of a mother's hair—about eight times the average level), was tied to about a 60 percent increase in a child exhibiting ADHD-like symptoms.

On the other hand, in women who ate a lot of fish (at least two servings per week), but who had lower concentrations of mercury in their hair, kids demonstrated a 60 percent lower than average risk for ADHD-like symptoms. The moms probably had lower mercury levels while still eating a lot of fish because they most likely ate fish with low mercury levels.

It should be pointed out that the study did not prove cause and effect, and did not use a formal diagnosis of ADHD (it just looked at ADHD-like symptoms). However, researchers still hope the study's findings can still provide insights into a condition that's estimated to affect 1 in 10 children in the United States.

And the takeaway for moms-to-be? "The really important message is to eat fish—just stay away from mercury-containing fish," Sharon Sagiv, the study's lead author, tells Reuters Health. That means avoiding the "big fishes," such as tuna, shark, halibut and swordfish, which typically contain the most mercury. Instead, stick to haddock, salmon, trout, and other smaller fish that are lower in mercury (a handy chart showing mercury content in fish can be found here). We're thinking baked salmon with wild rice sounds good for dinner tonight, what about you?