Shellfish have been used throughout the world for centuries. They are rich in low-fat protein, healthy fats and minerals. Eating shellfish on a regular basis can boost your immunity, help with weight loss, and enhance brain and heart health.
However, shellfish are one of the most common food allergens, and some species may contain pollutants and heavy metals.
This article discusses the different types of mollusks that they contain, the health benefits and possible harm.
Types of Shellfish
Shellfish are animals that live in water and have an outer shell or shell.
They can be divided into two groups: crustaceans and mollusks. Crustaceans include shrimp, crayfish, crab and lobster, while mollusks, scallops, oysters and mussels are examples of mollusks themselves ( 1 ).
Most mollusks live in salt water, but the name also refers to species found in fresh water.
Shellfish are available at grocery stores and restaurants around the world, but some regions are known for certain species. For example, lobsters are a popular food in the northeastern United States, while shrimp is a staple in dishes from the south of the country.
Most shellfish are steamed, baked or fried. Some – such as oysters and shellfish – can be eaten raw or partially cooked. Their taste varies from sweet to salty, from delicate to delicate – depending on the type and method of preparation.
The term “shellfish” includes shrimp, crayfish, crab, lobster, shellfish, scallops, oysters and mussels. Shellfish can be cooked in different ways and eaten around the world.
Rich Nutrient Profile
Shellfish are low in calories, but they are rich sources of low-fat protein, healthy fats and many trace elements.
Here is a comparison of three ounces (85 grams) of different types of shellfish ( 2 ):
|Shrimp||72||17 grams||0.43 g|
|Cancer||65||14 grams||0.81 grams|
|Crab||74||15 grams||0.92 g|
|Lobster||64||14 grams||0.64 g|
|Mollusks||73||12 grams||0.82 g|
|scallops||59||10 grams||0.42 g|
|oysters||69||8 grams||2 grams|
Moreover, shellfish are rich in iron, zinc, magnesium and vitamin B12 – they all play an important role in your body. For example, 3 ounces (85 grams) of oysters have almost 100% daily zinc intake ( 2 ).
Keep in mind that shellfish are most nutritious when steamed or baked. Breaded or fried shellfish may contain extra calories, refined carbohydrates, salt, and other unhealthy ingredients.
Shellfish are low in calories and rich in protein and omega-3 fatty acids. They also contain a large amount of certain trace elements, including iron, zinc, magnesium and vitamin B12.
Potential Health Benefits
Due to its impressive nutrient content, shellfish can be beneficial for your waist, brain, heart, and immune system.
May help lose weight
Shellfish are low in calories and high in protein and healthy fats, which makes them excellent food when trying to lose weight.
One study among overweight adults showed that those who ate more omega-3 fatty acids on a calorie-restricted diet felt significantly fuller after eating than those who ate less omega-3 on the same diet ( 9 )
May contribute to heart health
Shellfish are loaded with nutrients that can contribute to heart health, including omega-3 fatty acids and vitamin B12. This is a great benefit of shellfish, which is confirmed by research.
Several studies have linked the consumption of omega-3 fatty acids from fish and shellfish with a lower risk of heart disease. This is likely due to the fact that omega-3s have an anti-inflammatory effect ( 10 , 11 , 12 ).
One study of 18,244 healthy men in China found that those who consumed more than 7 ounces (200 g) of omega-3-rich shellfish per week were 59% less likely to die from a heart attack than those who ate less than 1. 74 ounces (50 grams) per week ( 13 ).
In addition, inadequate intake of vitamin B12 is associated with high levels of homocysteine in the blood, a protein that can increase the risk of heart disease. Therefore, eating foods rich in vitamin B12 can protect against heart disease ( 14 , 15 ).
Good for the brain
The same clam nutrients that are good for your heart are also important for brain health.
In fact, several studies have found that inadequate blood levels of vitamin B12 and omega-3 are risk factors for brain development problems in children and healthy brain function in adults ( 16 , 17 , 18 , 19 ).
Some studies also show that vitamin B12 and omega-3 fatty acids can enhance each other’s activity to enhance brain health.
One study among 168 elderly people with mild intellectual disabilities showed that B vitamins slow the progression of brain problems in those who have higher levels of omega-3 fatty acids in their blood than people with lower levels ( 20 ).
Rich in immunity enhancing nutrients
The advantage of shellfish is also that some of their species are loaded with zinc, an immunostimulating mineral.
This mineral is essential for the development of cells that make up the body’s immune defenses. It also acts as an antioxidant, protecting against damage from inflammation ( 21 ).
One study with 62 healthy adults over 90 years of age showed that zinc deficiency was associated with decreased activity of certain immune cells ( 22 ).
Regular consumption of shellfish, especially oysters, shellfish, mussels, lobsters and crabs, can improve zinc status and overall immune function.
Shellfish are loaded with protein and healthy fats, which can help weight loss. They are also rich in nutrients – omega-3 fatty acids, vitamin B12 and zinc – which contribute to a healthy brain, heart and immune system.
Even if the shellfish are very nutritious, their use may have some disadvantages.
The accumulation of heavy metals
Shellfish can accumulate heavy metals from the environment, such as mercury or cadmium.
People cannot emit heavy metals. Over time, the accumulation of these compounds in your body can lead to organ damage and other health problems ( 23 ).
One study found that shellfish in some areas may contain cadmium levels that are twice the recommended daily human intake. Shellfish may also contain mercury, but usually there are fewer than large fish ( 24 , 25 ).
The FDA recommends that adults consume 3–5 ounces (85–140 grams) of low-mercury fish twice a week. If the number of shellfish you eat per week is equal to or less than this value, then heavy metals should not be a concern ( 25 ).
Eating contaminated shellfish can lead to foodborne diseases.
In fact, seafood, such as shellfish, scallops, oysters, and mussels, accounted for more than 45% of seafood-related foodborne illnesses in the United States from 1973 to 2006 ( 26 ).
Shellfish food poisoning can be caused by bacteria, viruses, or parasites that enter the environment ( 26 ).
Pathogens breed in raw shellfish that are improperly chilled. Therefore, proper storage and preparation of shellfish can be an effective way to prevent foodborne diseases.
Pregnant and lactating women, the elderly and people with weakened immune systems should avoid raw or improperly prepared clams.
Shellfish allergy usually develops in adulthood, but can also occur in childhood.
Symptoms of an allergic reaction to shellfish include ( 29 ):
- Vomiting and diarrhea
- Abdominal pain and cramping
- Swelling of the throat, tongue, or lips
- Inconsistent breathing
In some cases, people with shellfish allergies may experience life-threatening anaphylactic shock, which requires immediate treatment ( 29 ).
Shellfish can contain various levels of heavy metals that can build up in your body and cause health problems. In addition, shellfish can cause foodborne diseases and allergic reactions.
Shellfish, which can be divided into crustaceans and mollusks, contain low-fat protein, healthy fats and trace elements.
The benefits of shellfish are that they can help you lose weight, boost your immune system, and improve your brain and heart health. However, shellfish may contain heavy metals and cause foodborne illness and allergic reactions.
Shellfish can be a nutritious and tasty addition to a balanced diet for the healthiest people.