Americans enjoy an average of 16 pounds of seafood and shellfish
every year. Among its chief benefits, seafood is a high-quality
source of protein, is low in fat, rich in many vitamins and
minerals. Seafood is also the source of most of the omega-3
fatty acids DHA and EPA -- which may help prevent heart disease
and more -- in the American diet, according to the Institute
Raw shellfish accounts for over 90 percent of cases
of seafood poisoning.
Raw shellfish, however, is also one of the food groups most
likely to cause food-borne illness. According to the Centers
for Disease Control and Prevention (CDC), "Because filter-feeding
shellfish strain microbes from the sea over many months, they
are particularly likely to be contaminated if there are any
pathogens in the seawater."
Meanwhile, seafood in general has received a lot of bad press
recently because of pollutants
like mercury, PCBs, and dioxins, which may contaminate
the flesh and cause health problems in humans.
Still, shellfish including oysters,
clams, mussels, scallops, shrimp, and more are enjoyed by
millions of Americans every year ... but are the potential
risks worth it?
The Pros and Cons of Shellfish
From a nutritional perspective, shellfish can be a healthy
part of your diet. From a contamination perspective, there
may be some risk involved, even outside of the potential for
mercury, PCBs and dioxins.
It's estimated that 20 million Americans eat raw shellfish,
according to the U.S. Food and Drug Administration (FDA),
and this accounts for over 90 percent of cases of seafood
"The biggest seafood hazard by far is raw or undercooked
shellfish," says Morris Potter of the CDC.
Though cooking shellfish will eliminate some of the
health risks, some toxins, such as the shellfish toxins
below, are not eliminated by cooking.
"One has to bear in mind that when you eat raw shellfish
you're eating a whole living organism complete with its GI
tract," Potter said. "That would be equivalent to
plucking a live chicken and eating it whole, guts and all."
The primary risks of shellfish include:
Norwalk virus, which comes from human sewage.
It can cause nausea, vomiting and diarrhea, and symptoms
usually resolve in a few days.
- Vibrio: Vibrio infections from eating raw shellfish
have increased a whopping 78 percent in the last decade,
according to the CDC. Vibrio is a bacteria common to the
warm waters of the Gulf of Mexico, and seafood that comes
out of that region is likely to contain it.
"Each year in the United States, Vibrio cause an
estimated 8,000 infections and 50 deaths," said Dr.
Nicholas A. Daniels of the University of California, San
Shellfish Toxins: Marine organisms called dinoflagellates
or diatoms are sometimes eaten or filtered by shellfish.
These organisms produce toxins that concentrate in the
bodies of shellfish. Though rare (the CDC estimates that
30 cases of poisoning by marine toxins are reported in
the United States each year), eating contaminated raw
shellfish can lead to:
Paralytic Shellfish Poisoning (PSP), which, in severe,
cases, can cause paralysis, respiratory failure and
death in two to 25 hours.
Diarrheic Shellfish Poisoning (DSP), which causes
diarrhea, nausea and vomiting that typically resolve
in a couple of days.
Neurotoxic Shellfish Poisoning (NSP), which causes
numbness, tingling in the arms and legs, loss of coordination,
muscle aches and upset stomach, all of which typically
resolve in two to three days.
Amnesic Shellfish Poisoning (ASP), which can result
in permanent short-term memory loss, seizures, paralysis
and even death in severe cases.
Hepatitis A, which typically only causes a mild,
short-term infection (you can have it and not even realize
So Should You Give Up, or Indulge in, Shellfish?
The answer is up to you. Many Americans do eat and enjoy
shellfish without becoming ill, but there is risk involved,
particularly if you intend to eat it raw.
Cooking shellfish will help to eliminate many, though not
all, of the risks.
Some people, however, are at higher risk of severe infections
should they come into contact with a contaminated clam or
oyster, and therefore should avoid eating all shellfish. This
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