Restaurant Sushi May Have More Mercury Than Store-Bought Fare
Toxin concentrations higher in certain tuna species versus others, study finds
(HealthDay News) -- The tuna sushi that you order in restaurants may
have higher concentrations of mercury than the sushi you buy at your
local supermarket, a new study finds.
Supermarkets tend to sell sushi made from yellowfin tuna,
which contains less mercury than other tuna species, researchers
"We found that mercury levels are linked to specific species,"
Jacob Lowenstein, a graduate student working with the American Museum
of Natural History in New York City, said in a news release from the
museum. "So far, the U.S. does not require restaurants and merchants to
clarify what species they are selling or trading, but species names and
clearer labeling would allow consumers to exercise greater control over
the level of mercury they [consume]," he added.
For their study, the researchers combined two efforts: DNA
barcoding performed at the museum to identify specific species; and a
mercury content analysis from experts at Rutgers University. The report
was published online April 21 in Biology Letters.
"People who eat fish frequently have a particular need to know
which species may be high in contaminants," said Michael Gochfeld,
professor at Robert Wood Johnson Medical School in New Jersey. "Some
agencies have been afraid that any mention of contaminants will
discourage people from eating any fish."
The team sampled sushi from 54 restaurants and 15 supermarkets
in New York, New Jersey and Colorado, and tested them for relative
mercury content. Through DNA barcoding, 100 samples were identified as
either bigeye tuna, yellowfin tuna or three different bluefin tuna
The team reported that all species tested exceeded or
approached mercury concentrations permissible by the United States, the
European Union, Japan and Canada, plus those set by the World Health
Higher mercury levels were found in bigeye tuna and bluefin
akami, which is a lean, dark red tuna, than in bluefin toro, a fatty
tuna, and yellowfin tuna akami, the researchers said. Mercury tends to
accumulate in muscle rather than fat, so mercury content is usually --
but not always -- higher in leaner fish. Yellowfin tuna, for example,
is lean, but may accumulate less mercury because it is smaller and
harvested earlier than other species, they said.
The seafood industry took a critical view of the report.
"This is a study that tests mercury levels in fish, but stops
short of any work exploring what -- if anything -- those levels mean
for health," said Gavin Gibbons, director of media relations at the
National Fisheries Institute, in an institute statement issued
He added that research has shown that "eating fish as a whole
food -- omega-3s, selenium, lean protein, traces of mercury and all --
is a boost to heart and brain health."
In addition, Gibbons said, the U.S. Food and Drug
Administration's mercury limit for seafood includes a 1,000 percent
safety factor, "and approaching that limit or even slightly exceeding
it does not equal health risk," he said.
To learn more about mercury in seafood, see the U.S. Environmental Protection Agency.
American Museum of Natural History, news release, April 21, 2010;
statement, National Fisheries Institute, April 21, 2010