Methylmercury bioaccumulation
Cognitive function improves with aerobic exercise, but not for people exposed to high levels of mercury before birth, according to research funded by the National Institute of Environmental Health Sciences (NIEHS), part of the National Institutes of Health. 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 the Harvard 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 197 participants are from Faroe Islands, 200 miles north of England, where fish is a major component of the diet. Their health has been followed since they were in the womb in the late 1980s. At age 22, this subset of the original 1,022 participants took part in a follow-up exam that included estimating VO2 max, or the rate at which they can use oxygen, which increases with aerobic fitness. Also, 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.
Results: higher VO2 max values were associated with better neurocognitive function, as expected based on prior research. Cognitive efficiency, including cognitive processing speed and short term memory, benefitted most from increased VO2 max.
But when divided into 2 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 <35 micrograms/L 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 U.S. Food and Drug Administration recommends that children and women of childbearing age eat 2-3 weekly servings of fish low in mercury as part of a healthy diet eg salmon, shrimp, pollock, canned light tuna, tilapia, catfish, and cod. 4 types should be avoided due to high mercury levels—tilefish from the Gulf of Mexico, shark, swordfish, and king mackerel. https://www.nih.gov/news-events/news-releases/brain-benefits-aerobic-exercise-lost-mercury-exposure
Recent Comments