8 July, 2003
However, wild fish eaten raw excretes more Mercury than when it
is cooked as the damaged fats are harder for the body to process.
A diet full of fish could mean a diet full of mercury
By Jane E. Allen
Los Angeles Times
Mercury poisoning. Mercury occurs naturally but is mostly a
byproduct of coal-burning, mining and other industries. Once in
the water supply, it forms methyl mercury, which lingers in fish
flesh, making predator fish such as swordfish and halibut the most
Lee Flynn thought she had a healthy lifestyle. She was thin and
active and she ate well with lunches of tuna and fresh vegetables
and dinners of halibut, sea bass or swordfish.
Yet she spent more than a decade plagued by fatigue, stomachaches
and headaches, as if she had "a wicked hangover." Her
hair started falling out. Memory lapses made her think she was losing
"I really felt something was poisoning me, but I couldn't
find the source," said Flynn, 59.
The Sausalito, Calif., anthropologist and documentary filmmaker
eventually ended up in the office of Dr. Jane Hightower, a San Francisco
internist. When Hightower heard that Flynn was eating fish nine
times a week, she immediately ordered a blood test for mercury.
A heavy metal that accumulates in the flesh of fish, especially
the popular predatory varieties, mercury can also accumulate in
people who eat those fish.
The test's stunning result: Flynn's mercury level was 20.6 micrograms
per liter of blood. A safe level is about 5, according to the federal
Environmental Protection Agency.
Like Flynn, many adults and children may be unwittingly overdosing
on mercury, say Hightower and some public-health activists, and
it's likely that most of them are going undiagnosed.
In recent years, fish has become the food of choice for millions
of Americans trying to eat more healthfully, with per capita consumption
at about 15 pounds, a 20 percent increase since 1980.
People on weight-loss diets turn to fish as a lean alternative
to beef. Bodybuilders go for the protein; it's not unusual for them
to polish off entire cans of tuna. Others are drawn to the cardiovascular
benefits of omega-3 fatty acids in fish. Restaurants, meanwhile,
are expanding their portions, often serving as much as a pound at
a time (a normal portion is 3 or 4 ounces).
The health benefits are undeniable and some people may suspect
the warnings are overblown. Last month, researchers at the American
Psychiatric Association meeting announced that fish rich in omega-3s
may prevent depression late in pregnancy and after childbirth. A
study a week earlier in the journal Lancet found that children in
the Seychelles Islands whose mothers ate a lot of fish during pregnancy
showed no signs of health problems.
Not all doctors 'think fish'
Even though the federal government and the state of Washington
have advised pregnant women to limit their fish intake, some people
still don't get the message or don't understand the cumulative effects.
Furthermore, physicians aren't trained to "think fish"
when patients complain of mental fuzziness, fatigue, hair loss and
tingling hands and feet. Those symptoms also can point to thyroid
problems, multiple sclerosis, chronic fatigue syndrome or menopause.
Last November, Hightower published a report in the online journal
Environmental Health Perspectives, a publication of the National
Institutes of Health, on 123 patients, 89 percent of whom had excessive
mercury she traced to fish.
The study was one of the first to document mercury levels in people
eating more than two servings of fish a week. To date, Hightower
has documented 300 cases of elevated mercury levels in her patients,
including a 4-year-old girl practically living on canned tuna.
"Mercury is a known poison," Hightower says. "By
definition, this means it is harmful and can make one ill or even
Predators are most toxic
Mercury occurs naturally, but is mostly a byproduct of coal-burning,
mining and other industries. Once in the water supply, it forms
methyl mercury, which lingers in fish flesh. As big fish eat smaller
fish, they absorb more of the heavy metal, making predators such
as swordfish, shark, tuna and halibut among the most toxic; smaller
fish such as salmon and shellfish the least.
Although fresh tuna tends to have more mercury than canned varieties,
levels in canned tuna can vary from nearly undetectable to 1 part
per million, the level beyond which the Food and Drug Administration
prohibits its sale.
Methyl mercury is especially damaging to the developing brains
of fetuses and children. The FDA advises pregnant women to eliminate
shark, tilefish, king mackerel and swordfish, and limit eating of
other fish to 12 ounces a week.
The state of Washington recommends pregnant women also eliminate
fresh or frozen tuna steaks and restrict their intake of canned
But high mercury levels don't always produce symptoms.
Clarissa Lee, a 30-year-old preschool teacher from San Francisco,
was eating lots of swordfish, sea bass and halibut last summer while
visiting Boston, Martha's Vineyard and the Hamptons.
In August, she told her gynecologist that she and her husband wanted
to have a baby. The doctor heard about her fish consumption and
ran a mercury test. Lee's level was 37. Lee gave up fish for a while,
got her mercury levels down and now indulges in the occasional salmon.
As for Flynn, she gave up fish for almost two years. She now eats
fish a couple of times a month, but never touches the predators.
Her mercury levels are normal, her memory is back and she feels
"Do anything to excess," Lee says, "and that's when
you get into trouble."
Fish ranked by mercury levels
Americans are consuming more fish, a good source of low-fat
protein. But with increased consumption comes the potential for
higher exposure to mercury, a toxic heavy metal. Some fish are more
likely to contain high levels of mercury. Here are some examples.
The worst: These fish have the
highest mercury levels. Pregnant women, nursing mothers and small
children are advised to avoid them. King mackerel,
shark, swordfish, tilefish, tuna.*
In between: These fish can be high
in mercury; they should be consumed only occasionally. Halibut,
lobster, mahi-mahi, orange roughy, red snapper.
The best: These fish tend to have
the lowest mercury levels. But some may still contain other contaminants,
including PCBs. Catfish, flounder, sole, salmon,
sardines, shellfish (includes clams, crab, oysters and shrimp),
*The state of Washington includes tuna on its list of fish that
pregnant women should avoid; the federal government puts it on the
Sources: USDA Office of Seafood; Food and Drug Administration;
Environmental Protection Agency; Washington State Department of