Diet, Fitness, and Exercise: Two Reports Offer Guidance on Eating Fish
Eat fish.
That's the take-home message of two reports on seafood out this week. But one is less enthusiastic than the other, and environmental and consumer groups are questioning some of the details.
The offering by the Institute of Medicine, high on fish but cautious, notes that fish in general and particularly species rich in omega-3 fatty acids such as salmon and anchovies may protect against cardiovascular disease. "There was circumstantial evidence" but no absolute proof, says Jose Ordovas of the Friedman School of Nutrition Science and Policy at Tufts University and a member of the IOM committee that produced the report. (It might simply be that people who eat fish have less room for hamburgers, or that they tend to live more healthy lifestyles in general.) The study published in the Journal of the American Medical Association, by contrast, went so far as to put a number on the benefit: A review of previous studies found that eating one or two servings of fish a week cut the risk of dying because of heart problems by 36 percent, and of death from all causes by 17 percent.
Both reports also deal with risks posed by contaminants like mercury. The IOM committee's recommendations are similar to previous government guidelines: Women who are pregnant or nursing, or who may become pregnant, as well as kids under 12, should cap their fish consumption at 12 ounces per week and avoid predatory fish—namely shark, swordfish, tilefish, and king mackerel. Contaminants can accumulate in these fish because they eat smaller fish that may also be contaminated. Six ounces of the total can be canned albacore tuna, which also tends to be high in mercury. Everyone else should choose a variety of seafood if they consume more than two servings a week. In the view of the Harvard School of Public Health team responsible for the JAMA report, cardiac benefits override any potential harmful effect of mercury and other contaminants like dioxins and polychlorinated biphenyls, known as PCBs. With the exception of the few species that women of childbearing age should avoid, "the benefits of fish intake exceed the potential risks," the authors say.
Critics point out that neither report offers guidance on other kinds of fish based on their level of nutrients and risk of contamination, or on which species are endangered. Consumers Union, the consumer advocacy group, says studies have shown that mercury levels in canned tuna can vary greatly and at times are as high as in the predatory fish named by the reports. The group recommends that pregnant women entirely avoid all kinds of tuna and that kids and women of childbearing age reduce their canned tuna consumption. And while it wasn't a goal of the studies to address the possible environmental impact of fishing, many consumers try to avoid buying species that are threatened. Some organizations, including Monterey Bay Aquarium, publish regional guides to eating fish that take scarcity into account.
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