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Stay with low mercury fish for brain health

Harold Mandel's picture
Delicious salmon

Aerobic exercise is associated with improved cognitive function, but not for people who are exposed to high levels of mercury prior to birth, according to research which was funded by the National Institute of Environmental Health Sciences (NIEHS), part of the National Institutes of Health.


It has become clear that aerobic exercise benefits brain health. However the benefits of aerobic exercise for the brain are lost if the fish is loaded with mercury.

The NIH/National Institute of Environmental Health Sciences reports that mercury exposure results in a loss of the brain benefits of aerobic exercise. The improvements in cognitive function which are generally seen with aerobic exercise are not seen in people who have been exposed to high levels of mercury prior to being born.

High prenatal exposure to methylmercury undermines benefits of exercise

Adults who are found to have had high prenatal exposure to methylmercury have not experienced the quicker cognitive processing and improved short term memory benefits of exercise which have been seen in people with low exposures to methylmercury. This methylmercury primarily comes from maternal consumption of fish which has high mercury levels.

Mercury has been found to come from industrial pollution found in the air which falls into the water. In the water it turns into methylmercury and than has been found to accumulate in fish. Prenatal exposure to methylmercury has toxic effects on the development of the brain and nervous system. Scientists at the Harvard T.H. Chan School of Public Health think this may undermine the ability of nervous system tissues to grow and develop well in response to aerobic fitness.

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Gwen Collman, Ph.D., director of the NIEHS Division of Extramural Research and Training, says it is clear neurodevelopment is a sensitive process which is particularly sensitive to methylmercury and other environmental toxins. The lifelong ripple effects of such exposures have been observed. It's effects on cognitive function in adults is of concern.

Collman points out that clearly aerobic exercise is a significant part of a healthy lifestyle. However now it seems that exposure to pollutants early in life may decrease the possible benefits. It is important to pay special attention to the environment which is created for pregnant mothers and babies.

Shrmip and salmon are among healthy varieties of low mercury fish

It has been recommended by the U.S. Food and Drug Administration that children and women who are of childbearing age eat two to three servings a week of fish which iis low in mercury as a part of a diet which is healthy. Shrimp, salmon, catfish, pollock, canned light tuna, tilapia, and cod are low mercury fish. Fish which should be avoided due to unusually high levels of mercury include shark,tilefish from the Gulf of Mexico, swordfish, and king mackerel.

This study has been published in the journal Environmental Health Perspectives. Increased aerobic capacity has been observed to be associated with improved performance in short-term memory and speed of processing. This positive association seems to be undermined by prenatal methylmercury exposure. It is therefore advisable to eat only fish with low levels of mercury.

Conclusions: Higher