Brain Benefits of Aerobic Exercise Lost to Mercury Exposure

The FDA recommends that children and women of childbearing age eat 2 to 3 weekly servings of fish low in mercury as part of a healthy diet.

Cognitive function improves with aerobic exercise, but not for people exposed to high levels of mercury before birth, according to research funded by NIEHS. Adults with high prenatal exposure to methylmercury, which mainly comes from maternal consumption of fish with high mercury levels, did not experience the faster cognitive processing and better short term memory benefits of exercise that were seen in those with low prenatal methylmercury exposures.

This is one of the first studies to examine how methylmercury exposure in the womb may affect cognitive function in adults. Mercury comes from industrial pollution in the air that falls into the water, where it turns into methylmercury and accumulates in fish. The scientists, based at Harvard’s T.H. Chan School of Public Health, suspect that prenatal exposure to methylmercury, known to have toxic effects on the developing brain and nervous system, may limit the ability of nervous system tissues to grow and develop in response to increased aerobic fitness.

The findings were published Sept. 9 in the journal Environmental Health Perspectives.

“We know that neurodevelopment is a delicate process that is especially sensitive to methylmercury and other environmental toxins, but we are still discovering the lifelong ripple effects of these exposures,” said Dr. Gwen Collman of NIEHS. “This research points to adult cognitive function as a new area of concern.”

The Food and Drug Administration recommends that children and women of childbearing age eat 2 to 3 weekly servings of fish low in mercury as part of a healthy diet. Low-mercury fish include salmon, shrimp, pollock, canned light tuna, tilapia, catfish and cod. Four types of fish should be avoided because of typically high mercury levels—tilefish from the Gulf of Mexico, shark, swordfish and king mackerel.