women of childbearing age in the U.S., fish consumption has increased in recent
years while blood mercury concentrations have decreased, suggesting improved
health for women and their babies, a new study shows.
research at Oregon State University also indicates fish consumption advisories
tailored to specific regions and ethnic groups would help women of childbearing
age to eat in even more healthy ways, including better monitoring of mercury
from the ocean has a unique and valuable nutritional profile. Among seafood's
many benefits are the omega-3 fatty acids that promote neurodevelopment, and
the nutrients in seafood are especially important for pregnant women to pass on
to developing fetuses.
the main way people are exposed to toxic methylmercury -- a mercury atom with a
methyl group, CH3, attached to it -- is through eating seafood. Thus the need
for precise, nuanced fish consumption advisories, said Leanne Cusack of Oregon
State University, the corresponding author on the study.
less-toxic elemental mercury enters the ocean from natural sources such as
volcanic eruptions and also from human activities like the burning of fossil
fuels, which accounts for about two-thirds of the mercury that goes into the
in the ocean, the mercury is methylated, diffuses into phytoplankton and passes
up the food chain, accumulating along the way.
scallop or a shrimp, for example, can have a mercury concentration of less than
0.003 parts per million. A large predator like a tuna, on the other hand, can
contain roughly 10 million times as much methylmercury as the water that
surrounds it and have a concentration of many parts per million.
how the mercury in the ocean becomes methylated, scientists don't know.
advisories are usually aimed at women of childbearing age because a developing
fetus has greater sensitivity to the neurotoxic effects of methylmercury.
Jointly, the U.S. Environmental Protection Agency and the Food and Drug
Administration recommend women in that group eat two meals of low-mercury fish
data from the ongoing National Health and Nutrition Examination Survey,
Cusack's research group looked at fish consumption patterns with regard to
blood mercury levels in U.S. women of childbearing age from 1999 to 2010.
were recently published in the journal Environmental Health.
in the coastal regions, particularly the Northeast, were found to have the
highest blood mercury concentrations; women living away from the sea,
especially in the inland Midwest, had the lowest.
residents also ate fish the most frequently, with the species consumed varying
by region. The type of fish most often consumed was shellfish in every part of
the U.S. except for the inland West and inland Midwest.
women's age and household income increased, so did their fish consumption
frequency and blood mercury concentrations. Among ethnic groups, Asian Americans,
Pacific Islanders, Alaska Natives and Native Americans ate fish the most often
and showed the most mercury, and Mexican Americans consumed fish the least
often and showed the smallest concentration of mercury.
also found total monthly fish consumption by women of reproductive age was
higher than it had been in recent years, with women consuming more marine fish
and shellfish but with no appreciable difference in the mean consumption of
freshwater fish, tuna, swordfish and shark," said Cusack, a postdoctoral
scholar in OSU's College of Public Health and Human Sciences.
encouraging because marine and shellfish are associated with smaller increases
in blood mercury. And also encouragingly, an average women who'd eaten fish
nine or more times in the previous month had lower blood mercury levels than
women who'd had fish at the same rate in 1999-2000."
differences in consumption and mercury levels by race and region illustrate the
need for tailored fish advisories, she said.
need to have information about fish types and quantities you can safely
eat," Cusack said. "The more detailed they can be, the better.
main thing is we do need to increase fish consumption in this
demographic," Cusack added. "It has been increasing since 1999, but
it's still not at the level where we want to see it. People need to start
consuming fish, and advisories need to focus on the benefits of consumption and
not just the risks by providing a broad range of fish that are low in
methylmercury and high in omega-3's."