Health Library

All About Shellfish

IMAGE Lobster, crabs, and shrimp, oh my! Should I eat them if my cholesterol is high? Bad poetry aside...there is no reason to clam up about your health concerns. However, shellfish can be part of a healthful diet. Here is a lobster pot full of facts about shellfish. No squidding!

Types of Shellfish

It is as simple as it sounds—shellfish are sea creatures that have a shell. They include:

  • Crustaceans, such as:
    • Crabs
    • Crayfish
    • Lobster
    • Shrimp
  • Mollusks, such as:
    • Abalone and snails
    • Clams, scallops, mussels, and oysters
    • Octopus and squid

Shellfish and Cholesterol

Cholesterol levels can raise the risk of heart disease. For this reason, many people stopped eating foods high in cholesterol, such as shellfish. However, cholesterol in food does not appear to affect cholesterol levels. Foods high in saturated (animal-based) fat, however, can. The good news is that shellfish is low in saturated fat.

The Secret is in the Sauce or Batter

How you prepare shellfish, however, makes the difference. Shellfish are often served with melted butter or a mayonnaise-based tartar sauce. And shellfish are frequently battered and deep fried. Both actions can turn a low-fat dish into a high-fat bomb. Instead, try steaming shellfish and serving with lemon and spices.

Shellfish Allergies

Shellfish allergies are common. Reactions usually appear within minutes to a few hours—or even as long as 24 hours. Reactions can happen after eating shellfish. They can also appear after inhaling cooking vapors or handling shellfish. Common symptoms are:

  • Stuffy nose, wheezing, or problems breathing
  • Hives, itching, and swelling
  • Gas, cramps, or upset stomach, or loose stools
  • Wheezing or problems breathing
  • Throat closing
  • Light-headedness or fainting

If you have a shellfish allergy, do not eat any foods or products that contain shellfish. Make sure you read a product's label. Shellfish may be a minor ingredient.

Shellfish Poisoning

Food poisoning can happen after eating tainted shellfish. This is more common with clams and mussels. Symptoms may begin as soon as 30 minutes after eating. They may include:

  • Tingling and numbness around the lips
  • Staggering
  • Changes in behavior
  • Problems speaking

In severe cases, shellfish poisoning may lead to seizures, coma, or death. If you suspect shellfish poisoning, get medical help right away.

The sickness is most often caused by a toxin that the shellfish has eaten. These toxins cannot be destroyed through cooking. To protect yourself, buy seafood from good quality sellers.

Mercury Content

Like certain types of fish, some shellfish have high levels of mercury. Mercury is a heavy metal. If eaten too often, it can build up in the body. A buildup of too much mercury can affect the nervous system. The level of mercury in shellfish varies. Lobster is moderately high in mercury. Clams, scallops, crabs, crayfish and squid have lower amounts. Shrimp and oysters have little to no mercury content. Mussels vary in mercury content.

Guidelines for Cooking Shellfish

Seafood should be cooked so that the inner temperature is 145°F (63ºC). Here is how shellfish should appear when properly cooked:

  • Shrimp and lobster—The flesh should be pearly-opaque.
  • Scallops—The flesh should look milky white/opaque and firm.
  • Clams, mussels, oysters—When the shells open, they are done. Throw out any that do not open.

Resources

Eat Right—Academy of Nutrition and Dietetics
http://www.eatright.org

Food Safety
http://www.foodsafety.gov

Canadian Resources

Dietitians of Canada
http://www.dietitians.ca

Health Canada
https://www.canada.ca

References

Food poisoning from marine toxins. Centers for Disease Control and Prevention website. Available at: https://wwwnc.cdc.gov/travel/yellowbook/2020/preparing-international-travelers/food-poisoning-from-marine-toxins. Accessed October 21, 2021.

Fresh and frozen seafood: selecting and serving it safely. US Food and Drug Administration website. Available at: https://www.fda.gov/food/buy-store-serve-safe-food/selecting-and-serving-fresh-and-frozen-seafood-safely. Accessed October 21, 2021.

Mercury levels in commercial fish and shellfish. US Food and Drug Administration website. Available at: https://www.fda.gov/food/metals-and-your-food/mercury-levels-commercial-fish-and-shellfish-1990-2012. Accessed October 21, 2021.

Safe minimum cooking temperatures. FoodSafety.gov website. Available at: https://www.foodsafety.gov/food-safety-charts/safe-minimum-cooking-temperature. Accessed October 21, 2021.

Shellfish allergy. Cleveland Clinic website. Available at:https://my.clevelandclinic.org/health/diseases/11319-allergies-shellfish. Accessed October 21, 2021.

  • EBSCO Medical Review Board
  • 202110
  • 20211021