News reports last week about a Food and Drug Administration report have environmentalists and public health officials worried that the agency wants to relax warnings about eating mercury-contaminated fish. A leaked draft report, obtained by the Washington Post, suggests that the benefits of eating fish may outweigh the risks of ingesting mercury even for pregnant women and children.
A quick reaction from the Environmental Protection Agency expressed "serious concerns" about the "scientifically flawed" report and, invoking the holy grail of scientific rigor, reiterated the agency's stance that mercury contamination cannot be taken lightly.
FDA officials say they're not preparing to change the guidelines but simply soliciting comments from other government scientists, according to an e-mail from FDA spokeswoman Stephanie Kwisnek.
The EPA and environmental activists appear skeptical. "It's important to note these comments -- from EPA -- have been very negative," says Sonya Lunder, a senior analyst at the nonprofit Environmental Working Group. The advocacy organization, which has seen both the draft report and the EPA response, is adamantly opposed to any attempt to ease the warnings about mercury in fish.
The apparent clash between the two agencies is a turnaround from four years ago when they issued a joint advisory with specific fish-consumption recommendations for groups at the highest risk for mercury-related health problems: women who are pregnant or nursing, women who might become pregnant and children. That advice included avoiding shark, swordfish, king mackerel and tilefish -- four fish species with the highest levels of mercury. The advisory also set an upper limit for eating seafood of any kind at two 6-ounce servings per week for those groups.
The science behind the policy is tricky. It's hard enough for epidemiologists to correlate one dietary factor to a health outcome. In this case, policymakers must assess what's known about two components of fish -- mercury and omega-3 fatty acids -- which have opposing effects on normal child development. Studies often look at either the risk of mercury intake or the benefit of fish eating, but rarely both.
It's true that people accumulate mercury in their bodies from eating contaminated fish. For most adults, there is little concern about the levels of mercury found even in a fish-filled diet. For fetuses and babies, however, mercury can easily have toxic effects on the nervous system, says Kathryn Mahaffey, a lecturer at the George Washington School of Public Health in Washington, D.C. Formerly a senior scientist at the EPA, Mahaffey led the agency effort to define a benchmark mercury level for the 2004 advisory.
It also is true that eating fish is good for you. It's a good source of protein and omega-3 fatty acids, which are "critical in the development of the nervous system," says William McCarthy, professor of public health at UCLA. "So our babies, if we want them to have well-functioning brains, absolutely need the omega-3s."
What's hard to say is how the pluses and minuses add up. "The FDA/EPA guidelines were considering the risks of mercury primarily as a contaminant but did not consider the benefits of the nutrients of fish, which may offset the risks of mercury," says Dr. Emily Oken, a physician and assistant professor at Harvard Medical School in Boston. "Because at that time, there had not been any studies that looked at the overall effect of fish during pregnancy."
Says Lunder: "There are some benefits to eating fish and there are obviously drawbacks like mercury, and the way to maximize that is to steer people to the best species," which the current guidelines do.
(For more information on mercury levels~frf/sea-mehg.html in different fish, go to the FDA website. For advisories on local fish consumption, go to the California Office of Environmental Health Hazard Assessment's site. )
Lunder cites a recent study of Mahaffey's, based on National Health and Nutrition Examination Survey data from 1999 to 2004 and published online in Environmental Health Perspectives in August, that showed mercury levels in American women are dropping steadily, but omega-3 levels and fish consumption are holding steady.
"It shows that [the current] guidance is working and people are getting the message and avoiding the highest mercury fish," Lunder says. A reversal of that advice would raise mercury exposure, she says, putting kids at risk.
McCarthy points out that fish are not the only good source of omega-3 fatty acids. Significant plant sources of the nutrient include flax seed, walnuts, pecans, cauliflower, broccoli, Brussels sprouts, tofu, kale and collard greens.
Until the government agencies sort out the science, the current guidelines for eating fish stand.