Warnings about fish consumption and mercury overstated

A comparison of the risks and benefits of fish consumption suggests that government advisories warning women of childbearing age about mercury exposure should be issued with caution. The study warns that if advisories cause people to eat less fish out of fear about the effects of mercury, substantial nutritional benefits could be lost. The study will appear as a series of five articles in the November issue of the American Journal of Preventive Medicine.
“Fish are an excellent source of omega-3 fatty acids, which may protect against coronary heart disease and stroke, and are thought to aid in the neurological development of unborn babies,” said Joshua Cohen, lead author and senior research associate at the Harvard Center for Risk Analysis at the Harvard School of Public Health (HSPH). “If that information gets lost in how the public perceives this issue, then people may inappropriately curtail fish consumption and increase their risk for adverse health outcomes.”

Fish are a major source of mercury exposure, a neurotoxin that may cause subtle developmental effects in utero, like the loss of a fraction of an IQ point, even at the modest exposure levels typical of the American population. As a result, the U.S. Food and Drug Administration (FDA) and Environmental Protection Agency (EPA) have issued advisories warning women of childbearing age about mercury in fish.

Because fish are also a good source of omega-3 fatty acids, the advisories have had to walk a fine line. The most recent U.S. government advisories emphasize that other adults need not worry about mercury in fish. They even advise women of childbearing age to keep eating fish, although they caution that group to keep away from some species (shark, swordfish, king mackerel, and tilefish) likely to contain more mercury and to limit total fish intake to about two meals a week.