Adults with high levels of prenatal exposure to methylmercury did not experience the same brain benefits from aerobic exercise as those with low levels of exposure, suggests a National Institutes of Health-funded study.

The benefits included faster cognitive processing and better short-term memory.

Mercury comes from industrial pollution in the air that falls into the water, where it turns into methylmercury and accumulates in fish. The high prenatal exposure mainly comes from maternal consumption of such fish, per a media release from NIH/National Institute of Environmental Health Sciences (NIEHS).

This prenatal exposure may limit the ability of nervous system tissues to grow and develop in response to increased aerobic fitness, the release continues.

In a study published in Environmental Health Perspectives, researchers based at the Harvard T.H. Chan School of Public Health followed 197 study participants from the Faroe Islands, 200 miles north of England, where fish is a major component of the diet. The participants’ health has been followed since they were in the womb in the late 1980s.

At age 22, they took part in a follow-up exam that included estimating the participants’ VO2 max, or the rate at which they can use oxygen, which increases with aerobic fitness. Also, a range of cognitive tests were performed related to short-term memory, verbal comprehension and knowledge, psychomotor speed, visual processing, long-term storage and retrieval, and cognitive processing speed, the release explains.

Overall, the researchers found that higher VO2 max values were associated with better neurocognitive function, as expected based on prior research. Cognitive efficiency, which included cognitive processing speed and short-term memory, benefitted the most from increased VO2 max, the release explains.

But when the researchers divided the participants into two groups based on the methylmercury levels in their mothers while they were pregnant, they found that these benefits were confined to the group with the lowest exposure. Participants with prenatal methylmercury levels in the bottom 67%, or levels of less than 35 micrograms per liter in umbilical cord blood, still demonstrated better cognitive efficiency with higher VO2 max. However, for participants with higher methylmercury levels, cognitive function did not improve as VO2 max increased, the release continues.

“We know that aerobic exercise is an important part of a healthy lifestyle, but these findings suggest that early-life exposure to pollutants may reduce the potential benefits,” says Gwen Collman, PhD, director of the NIEHS Division of Extramural Research and Training, in the release.

“We need to pay special attention to the environment we create for pregnant moms and babies,” she adds.

[Source(s): NIH/National Institute of Environmental Health Sciences, Science Daily]