Benefits of Fish Intake
Outweigh Potential Risks, Reports Say
MARY ANN MOON (Contributing Writer)
The benefits of fish consumption exceed the potential risks
in adults, according to two reports.
The public is aware of the potential harm from mercury,
dioxins, and polychlorinated biphenyls (PCBs) in fish, but is confused about who
is at risk and which species to avoid. If this confusion over the risks and
benefits of fish consumption leads people to avoid moderate intake, it “could
result in thousands of excess CHD [coronary heart disease] deaths annually,”
concluded the study's authors, Dr. Dariush Mozaffarian and Eric B. Rimm, Sc.D.,
of Brigham and Women's Hospital and Harvard Medical School, Boston.
The study was published in the Journal of the American
Medical Association the day after the results of an Institute of Medicine (IOM)
report on seafood safety, which came to similar conclusions, were announced in
Washington. The report, sponsored by the National Oceanic and Atmospheric
Administration (NOAA) and the Food and Drug Administration, concluded that
seafood is safe and nutritious, and should be part of the diet to reduce the
risk of dying from coronary heart disease, Bill Hogarth, Ph.D., director of the
NOAA Fisheries Service, said during a teleconference held to discuss the results
of both the report and the study.
For the general population, those who eat more than two
servings a week of seafood should eat a variety of species to avoid accumulated
exposure to environmental contaminants and to benefit from the various nutrients
in different species, according to the IOM report.
Children who are aged 12 and under and women who are
pregnant or nursing or who may become pregnant can safely eat 12 ounces of fish
per week, but should avoid four species—shark, tilefish, swordfish, and king
mackerel—that contain higher levels of mercury, according to the IOM report.
Dr. Mozaffarian, who also spoke at the press conference,
said that the recommendations made in his paper were similar to those found in
the IOM report. People should not avoid fish because of concerns over safety, he
said, adding, “we found for the general population, the health benefits in terms
of lowering risk from dying from a heart attack were much greater than the
health risks, so our recommendations are to eat a variety of seafood, one to two
servings a week,” especially of oilier fish that are high in omega-3 fatty
acids.
People who eat fish frequently should eat a variety of
seafood, and women of childbearing age, who are nursing or are pregnant, and
younger children, should avoid the four species with higher mercury levels.
In the study, which Dr. Mozaffarian said was funded by the
National Institutes of Health, he and Dr. Rimm reviewed all published scientific
papers that evaluated fish intake and cardiovascular risk, the effects of
methylmercury exposure, and the health risks posed by dioxins and PCBs in
seafood. They focused on the reports from randomized clinical trials and large
prospective studies.
Compared with little or no fish intake, modest consumption
of fish or fish oil decreases the relative risk of CHD death by 36%, according
to the analysis. Such consumption would reduce total mortality in a mixed
population by an estimated 9%–18%.
“This can be compared to effects of statins on total
mortality—a 15% reduction—in a metaanalysis of randomized trials,” they said (JAMA
2006;296:1885–99).
In the general population, a weekly intake of 1,500–2,000
mg (one 6-oz serving) of oily fish, such as wild or farmed salmon, anchovies, or
herring, or more frequent consumption of other fish would provide reasonable CHD
benefit.
On the other side of the equation, methylmercury does not
appear to pose significant risks except in specific species (shark, swordfish,
golden bass, king mackerel, albacore tuna, and local catches from contaminated
areas) and in specific populations (women of childbearing age, nursing mothers,
and young children). Even these risk groups can avoid harmful mercury exposure
while maintaining a moderate fish intake “by simply consuming a variety of
different seafood,” the researchers said.
Levels of dioxins and PCBs in fish were found to be low.
These substances pose potential cancer risks, but they are well exceeded by CHD
benefits. For example, “CHD benefits outweighed cancer risks by 100- to 370-fold
for farmed salmon and by 300- to more than 1,000-fold for wild salmon,” Dr.
Mozaffarian and Dr. Rimm wrote in the study.
Noncancer risks of dioxins and PCBs, such as possible
immune system or neurologic effects, “would have to exceed additional possible
benefits by more than 100-fold to meaningfully alter the present estimates of
risks vs. benefits,” they added. Their findings demonstrate that the potential
risks of fish consumption “must be considered in the context of potential
benefits,” they concluded.
