Shellfish – which can be
divided into crustaceans and mollusks – are rich in lean protein, healthy fats,
and micronutrients.
Shellfish have been
consumed all over the world for centuries.
They are rich in lean
protein, healthy fats, and minerals. Eating shellfish regularly can boost your
immunity, help with weight loss, and promote brain and heart health.
However, shellfish are
one of the most common food allergens, and some species may contain
contaminants and heavy metals.
This article reviews
the different types of shellfish, their nutritional, health benefits, and
possible dangers.
Species of shellfish
As the name suggests,
shellfish are animals that live in water and have a shell or shell-like appearance.
They can be divided
into two groups: crustaceans and mollusks. Crustaceans include shrimp,
crayfish, crabs, and lobsters, while clams, scallops, oysters, and mussels are
examples of mollusks (1).
Most shellfish live in
brackish water, but the name also refers to species in freshwater.
Shellfish can be
bought in grocery stores and restaurants around the world, but some areas are
known for certain species. For example, lobster is a popular food in the
northeastern United States, while shrimp is a staple of the country's southern
cuisine.
Most types of
shellfish can be eaten steamed, roasted, or fried. Some — like oysters and
clams — can be eaten raw or half-cooked. Their taste ranges from sweet to
salty, from subtle to delicate – depending on the type and cooking method.
Summary: the term "shellfish" includes
shrimp, crayfish, crabs, lobsters, clams, scallops, oysters, and mussels. Shellfish
can be made in different ways and are eaten all over the world.
A Nutritious powerhouse
Shellfish are low in
calories and are rich in lean protein, healthy fats, and many micronutrients.
This is a nutritional
comparison of different types of shellfish in 3 ounces (85 grams) servings (2):
type |
calorie |
protein |
fat |
shrimp |
72 |
17 g |
0.43 g |
crayfish |
65 |
14 g |
0.81 g |
crab |
74 |
15 g |
0.92 g |
lobster |
64 |
14 g |
0.64 g |
clam |
73 |
12 g |
0.82 g |
scallops |
59 |
10 g |
0.42 g |
oysters |
69 |
8 g |
2 g |
mussels |
73 |
10 g |
1.9 g |
Most of the fat in
shellfish is found in the form of omega-3 fatty acids, which have a range of
health benefits, such as improved brain and heart health (4, 5).
What's more, shellfish
are rich in iron, zinc, magnesium, and vitamin B12 — all of which play an
important role in your body. For example, 3 ounces (85 grams) of oysters
contain almost 100% of their daily value (DV) of zinc (2).
Keep in mind that
shellfish are most nutritious when steamed or roasted. Breadcrumbs or fried
shellfish may contain extra calories, refined carbohydrates, added salt, and
other unhealthy ingredients.
Summary: Shellfish are low in calories and rich in
protein and omega-3 fatty acids. They also contain large amounts of certain
micronutrients, including iron, zinc, magnesium, and vitamin B12.
Potential health benefits
Because of their
impressive nutritional profile, shellfish may be good for your waistline,
brain, heart, and immune system.
May help with weight loss
Shellfish are low in
calories and are rich in lean protein and healthy fats – making them great
foods for weight loss.
Protein-rich foods
make you feel full and satisfied, which may prevent you from consuming too many
calories, which can help you lose or maintain weight (6, 7).
What's more, because
of their omega-3 fatty acid content, fish may cause greater satiety and
contribute to weight loss compared to other high-protein foods (8, 9).
A study of overweight
adults found that people who consumed more omega-3 fatty acids in a
calorie-restricted diet felt significantly fuller after meals than those who
consumed less omega-3s in the same diet. (9)。
May promote heart health
Shellfish are rich in
heart-healthy nutrients, including omega-3 fatty acids and vitamin B12.
Several studies have
shown that eating omega-3 fatty acids in fish and shellfish has been linked to
a reduced risk of heart disease. This may be because omega-3 has
anti-inflammatory effects (10, 11, 12).
A study of 18,244
healthy men in china found that people who consumed more than 7 ounces (200
grams) of omega-3 shellfish per week were 59% less likely to die of heart
disease than those who consumed less than 1.74 ounces (50 grams) per week (13).
In addition,
inadequate intake of vitamin B12 is associated with blood levels of
homocysteine, a protein that increases the risk of heart disease. Therefore,
consuming foods rich in vitamin B12 can prevent heart disease (14, 15).
Good for your brain
The same nutrients in
shellfish that are good for the heart are also essential for brain health.
In fact, several
studies have identified inadequate levels of vitamin B12 and omega-3 in the
blood as risk factors for brain development problems in children and healthy
brain function in adults. (16, 17, 18, 19)
Some studies have also
shown that vitamin B12 and omega-3 fatty acids may enhance each other's
activity, thereby promoting brain health.
A study of 168 older
adults with mild mental disorders found that B vitamins slowed the progression
of brain problems in people with higher levels of omega-3 fatty acids in their
blood compared to those with lower levels of omega-3 fatty acids in their
blood. (20)。
Rich in nutrients that enhance immune function
Some types of
shellfish are rich in zinc which boosts immune function.
This mineral is
necessary for the development of the cells that make up the body's immune
defenses. It can also act as an antioxidant, preventing damage caused by
inflammation (21).
A study of 62 healthy
adults over the age of 90 found that zinc deficiency was associated with
reduced activity of certain immune cells. (22)。
Eating shellfish
regularly — especially oysters, clams, mussels, lobsters, and crabs — can
improve your zinc status and overall immune function.
Summary: Shellfish are rich in protein and
healthy fats that may help with weight loss. They are also rich in nutrients
that promote brain, heart, and immune system health — omega-3 fatty acids,
vitamin B12, and zinc.
Possible drawbacks
Although shellfish are
rich in nutrients, there may be some drawbacks to eating them.
Accumulation of heavy metals
Shellfish may
accumulate heavy metals, such as mercury or cadmium, from their environment.
Humans cannot excrete
heavy metals. Overtime, the accumulation of these compounds in your body can
lead to organ damage and other health problems (23).
One study found that
cadmium levels in shellfish in some areas might be twice the recommended daily
intake for humans. Shellfish may also contain mercury but are usually
relatively large fish (24, 25).
The FDA recommends
that adults eat 3-5 ounces (85-140 grams) of low-mercury fish twice a week. If
you eat at least or less shellfish per week, heavy metals don't have to worry (25).
Foodborne illness
Consumption of
contaminated shellfish can lead to foodborne illness.
In fact, from 1973 to
2006, mollusks— such as clams, scallops, oysters, and mussels— accounted for
more than 45 percent of seafood-related foodborne illness cases in the United
States (26).
Shellfish food
poisoning can be caused by bacteria, viruses, or parasites acquired from their
environment (26).
Pathogens multiply in
large numbers in raw shellfish and improperly refrigerated shellfish. Therefore,
proper storage and cooking of shellfish is an effective way to prevent
foodborne illness.
Pregnant and lactating
women, the elderly, and people with compromised immune systems should avoid raw
or improperly prepared shellfish.
Anaphylaxis
Shellfish are one of
the top eight food allergens in the United States (27, 28).
Shellfish allergy
usually occurs in adulthood, but can also occur in childhood.
Symptoms of an
allergic shellfish reaction include (29):
- vomiting and diarrhea
- stomach pain and cramps
- swelling of the throat, tongue, or lips
- measles
- shortness of breath
In some cases, people
who are allergic to shellfish may experience life-threatening anaphylactic
shock that requires immediate treatment (29).
Summary: Shellfish may contain different levels of
heavy metals that can build up in your body and cause health problems. In
addition, shellfish can cause foodborne illness and allergic reactions.
Conclusion:
Shellfish – which can
be divided into crustaceans and mollusks – are rich in lean protein, healthy
fats, and micronutrients.
They may help with
weight loss, boost immunity, promote brain, and heart health. Nevertheless,
shellfish may contain heavy metals, cause foodborne illness, and allergic
reactions.
Still, shellfish can
be a nutritious and delicious addition to a balanced diet for the healthiest of
people.