advisories on fish consumption & mercury may do more harm than good

³The study found that if pregnant women were to eat the same amount of
fish but replace fish high in mercury with fish low in mercury,
cognitive development benefits, amounting to about 0.1 IQ points per
newborn baby, could be achieved with virtually no nutritional losses.
However, if pregnant women were to decrease their fish consumption by
one-sixth, the loss of omega-3 fatty acids during pregnancy would cut
the nutritional benefit by 80%.²

......................................

http://www.eurekalert.org/


Public release date: 19-Oct-2005
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Contact: Kevin C. Myron
kmyron@xxxxxxxxxxxxxxxx
617-432-3952
Harvard School of Public Health

Study finds government advisories on fish consumption & mercury may do
more harm than good


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.
In order to synthesize the available evidence, the Harvard project
convened a panel of experts, chaired by Steven Teutsch, a medical
epidemiologist formerly with the U.S. Centers for Disease Control and
Prevention and now at Merck and Company. Other panel members included
David Bellinger (Harvard University), William Connor (Oregon Health
Sciences University), Penny Kris-Etherton (Pennsylvania State
University), Robert Lawrence (Johns Hopkins University), David Savitz
(University of North Carolina), and Bennett Shaywitz (Yale University).
The panel identified important health effects to consider, assessed the
dose-response relationships between fish consumption (or its
constituents) and health outcomes, and developed an overall health
effects model. In addition to Joshua Cohen, Harvard scientific staff
included Colleen Bouzan and Ariane König, and principal investigator,
George Gray, executive director of the Harvard Center for Risk Analysis.
The study found that if pregnant women were to eat the same amount of
fish but replace fish high in mercury with fish low in mercury,
cognitive development benefits, amounting to about 0.1 IQ points per
newborn baby, could be achieved with virtually no nutritional losses.
However, if pregnant women were to decrease their fish consumption by
one-sixth, the loss of omega-3 fatty acids during pregnancy would cut
the nutritional benefit by 80%. If other adults were to also decrease
their fish intake by one-sixth, then risks from coronary heart disease
and stroke would increase. For example, among 65 to 74 year old men, the
annual mortality risk would increase by nearly 1 in 10,000.
The study also found that increasing fish consumption among individuals
who were not going to become pregnant would substantially decrease
stroke and coronary heart disease risks. Much of this benefit appears to
be associated with getting people to eat at least some fish (e.g., one
meal a week), rather than no fish at all.
Cohen explained that the problem with fish advisories is that we do not
know what their overall impact on the population might be. "Depending on
how the population reacts, that impact could very well be negative."
Because of the potential downside, Cohen urges the government to
carefully evaluate the pros and cons. He concluded, "Before the
government issues advisories, it needs to gather data on how people
actually will react, how those changes in behavior will influence
nutrient intake and exposure to contaminants, and how those changes in
intake and exposure will translate into changes in health. In other
words, before we put an intervention into action, we need to estimate
its real world impacts both its benefits and its countervailing risks."
The work was funded by a grant from the National Food Processors
Association Research Foundation (now the Food Products Association
Research Foundation) and the Fisheries Scholarship Fund.
The five articles and the introductory article from the American Journal
of Preventive Medicine will be available as PDFs shortly.

? "A Quantitative Analysis of Fish Consumption and Stroke Risk" by
Colleen Bouzan, MS, Joshua T. Cohen, PhD, William E. Connor, MD, Penny
M. Kris-Etherton, PhD, George M. Gray, PhD, Ariane König, PhD, Robert S.
Lawrence, MD, David A. Savitz, PhD, and Steven M. Teutsch, MD
? "A Quantitative Analysis of Fish Consumption and Coronary Heart
Disease Mortality" by Ariane König, PhD, Colleen Bouzan, MS, Joshua T.
Cohen, PhD, William E. Connor, MD, Penny M. Kris-Etherton, PhD, George
M. Gray, PhD, Robert S. Lawrence, MD, David A. Savitz, PhD, and Steven
M. Teutsch, MD
? "A Quantitative Analysis of Prenatal Methyl Mercury Exposure and
Cognitive Development" by Joshua T. Cohen, PhD, David C. Bellinger, PhD,
and Bennett A. Shaywitz, MD
? "A Quantitative Analysis of Prenatal Intake of n-3 Polyunsaturated
Fatty Acids and Cognitive Development" by Joshua T. Cohen, PhD, David C.
Bellinger, PhD, William E. Connor, MD, and Bennett A. Shaywitz, MD
? "A Quantitative RiskBenefit Analysis of Changes in Population Fish
Consumption" by Joshua T. Cohen, PhD, David C. Bellinger, PhD, William
E. Connor, MD, Penny M. Kris-Etherton, PhD, Robert S. Lawrence, MD,
David A. Savitz, PhD, Bennett A. Shaywitz, MD, Steven M. Teutsch, MD,
and George M. Gray, PhD

###
Harvard School of Public Health is dedicated to advancing the public's
health through learning, discovery, and communication. More than 300
faculty members are engaged in teaching and training the 900-plus
student body in a broad spectrum of disciplines crucial to the health
and well being of individuals and populations around the world. Programs
and projects range from the molecular biology of AIDS vaccines to the
epidemiology of cancer; from risk analysis to violence prevention; from
maternal and children's health to quality of care measurement; from
health care management to international health and human rights. For
more information on the school visit: www.hsph.harvard.edu

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