Eating one fish meal per week gives significant nutritional benefit
Boston, MA – 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 fish consumption in the general public to drop 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 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.
The Harvard project looked at whether the benefits of lower mercury exposure to pregnant women justified the loss of omega-3 fatty acids from decreased fish consumption. The project also went one step further, asking what would happen if the public did not follow the government’s recommendations exactly as they were intended. Although evidence on how people actually react to advisories is limited, one study found that pregnant women cut their fish consumption by one-sixth following a 2001 government advisory. Nor is it difficult to imagine that other adults, not targeted by the advisory, cut back on fish based on misperceptions about the risks.