Recently, separate reports were released from the Harvard School of Public Health (in the Journal of the American Medical Association) and by the Institute of Medicine on the health effects of eating fish.
The Harvard report, which was based on a review of medical literature, was all but glowing in its endorsement of fish. The authors concluded that a modest intake of fish and shellfish, defined as one or two servings per week, was associated with a significant drop in mortality from heart disease, and in overall mortality. They brushed off the potential health risks from mercury and other contaminants in seafood as being low, and in any case, being overwhelmed by the health benefits.
The IOM report was far less glowing in its endorsement of seafood. The IOM found, in an extensive 400-page report, that eating fish "may reduce people's overall risk for developing heart disease," but that firm data proving that fish can strongly impact health are lacking. Likewise, they cited a lack of objective evidence regarding the risks of eating seafood, and in particular, a lack of reliable information on the distribution of contaminants in seafood.
They concluded that it is probably healthful for most individuals to eat two 3-ounce servings of seafood per week, including up to 6 ounces of albacore tuna, but that large predatory fish such as shark, swordfish, tilefish or king mackerel should be avoided. These conclusions are consistent with prior recommendations released by the Food and Drug Administration.
An article in The New York Times picked up on the variance between these two high-profile reports, and described the reaction of several environmental and consumer groups to these reports. That reaction can be summarized as follows: both reports are objectionable because they underplay the risks associated with consuming seafood, in particular the risk of mercury. The Harvard report is additionally objectionable because it vastly overplays the benefits of eating seafood.
The IOM report is probably the one closest to the truth, since it has made everybody mad. The seafood industry would rather have us embrace the Harvard study, since it equates eating lots of seafood with near immortality. And environmental and consumer groups, which generally have become quite alarmist about the hazards of seafood, criticize the IOM report for its lack of alarm. (Forgive DrRich, who has come to think of environmental and consumer groups as political and activist organizations rather than as objective interpreters of science, and who believes their opinions, while often valuable, must be weighed in light of their inherent conflicts.)
The IOM report says, in essence, that despite the passions on both sides of the issue, neither the benefits nor the potential risks of eating seafood have been proven by objective science. Thus, it is reasonable (given the likely benefits) to eat modest amounts. It is also reasonable (given the potential risks) to limit one's consumption to modest amounts. Taking into account that there are certain kinds of seafood that perhaps ought to be avoided altogether, two servings a week seem about right.
Since this conclusion will spur neither an explosion in the profits of the seafood industry, nor in oppressive new regulations on industrial pollutants, it doesn't make anybody happy.
1) National Academy of Sciences. Seafood Choices: Balancing Benefits and Risks, executive summary.
2) Mozaffarian D, Rimm EB. Fish intake, contaminants, and human health. Evaluating the risks and the benefits. JAMA2006; 296:1885-1899.
3) Burros M. One study calls fish a lifesaver, another is more cautious. New York Times, October 18, 2006.