Shellfish

What is Shellfish?

  • Shellfish contain many beneficial nutrients including protein, omega-3s, and various vitamins and minerals. Children with ASD often have a decreased intake of shellfish and fish.

  • Shellfish is one of the top 8 food allergens, which makes it more likely that someone will react to them in some way [1].

  • There are two different groups of shellfish: crustaceans and mollusks. It is possible to only be allergic to one group and not the other, but most people are allergic to both. [2]

  • Individuals with autism are often seen to have low intakes of fish, shellfish, seaweed and vegetables. [4-5]

  • Food labeling laws in the United States only covers crustaceans and not mollusks, so be careful when trusting food packaging. [2]

Nutrient Breakdown

Different shellfish contain various amounts of nutrients, but in general, shellfish can be a good source of:

Foods Containing Shellfish

  • Crustaceans*

    • Lobster

    • Shrimp 

    • Crab

    • Prawns

    • Crawfish

  • Mollusks*

    • Clams

    • Scallops

    • Mussels

    • Oysters

  • Other:

    • Surimi (imitation shellfish)

    • Omega-3 supplements

    • Glucosamine

    • Calcium supplements made from oyster shells or coral

*Food labeling laws in the United States only covers crustaceans and not mollusks, so be careful when trusting food packaging. [2]

Shellfish Alternatives

  • See the protein note for other protein alternatives

  • See the Omega-3 note for other omega-3 sources

Food Reactions

Shellfish allergy is one of the top 8 most common allergies. Allergies are caused by an immune system response that identifies something as bad for your body and triggers the production of immunoglobulin E (IgE) antibodies. When someone has a shellfish allergy, it is the shellfish that causes this reaction. This response will continue to happen each time you are in contact with shellfish. The antibodies made will recognize the shellfish and trigger your body to produce histamine that causes the symptoms of an allergic reaction. The most dangerous of reactions is anaphylaxis. 

There are two different groups of shellfish, crustaceans and mollusks. It is possible to only be allergic to one group and not the other, but most people are allergic to both. 

Tests can confirm a shellfish allergy, and avoiding shellfish products is the best way to avoid the allergic reactions. Make sure to know exactly what is in the shellfish category, you may be surprised. [2]

The body can respond to foods in many different ways including food allergies, food sensitivities, or food intolerances. If you suspect a food reaction, you can either choose to avoid the food or seek food reaction testing. Click here more information on the difference in types of food reactions and testing options

DISCLAIMER: Always consult with your pediatrician and/or your Registered Dietitian to help you test for a food reaction or to aid you in making individualized dietary changes.

Shellfish & Autism in the Research

Intake of Shellfish in Autism

  • Individuals with autism are often seen to have low intakes of fish, shellfish, seaweed and vegetables. [4-5]

Risks of Shellfish Consumption

  • Cadmium, a metal found in shellfish, can cause adverse effects on the human nervous system if consumed in excess. There is no definite connection between cadmium blood concentrations causing ASD [7].

Maternal Intake of Shellfish

  • Domoic acid can be found in whole shellfish. The behaviors, brain anatomy and function of domoic acid exposure and ASD are similar. The human fetus in utero is very sensitive to domoic acid exposure. Excessive shellfish consumption during pregnancy may be a risk factor for ASD. [6]

  • Increased intake of shellfish in the second half of pregnancy is associated with autism traits in the child. [8]


  • Description[1] What You Need to Know about Food Allergies. U.S. Food and Drug Administration.https://www.fda.gov/food/buy-store-serve-safe-food/what-you-need-know-about-food-allergies. Published 2020. Accessed August 18, 2020.

    [2] Shellfish Allergy? You Need to Avoid These 19 Different Sea Creatures. Verywell Health. https://www.verywellhealth.com/shellfish-allergy-diet-foods-to-avoid-1324478. Published 2020. Accessed August 31, 2020.

    [3] 2020. [online] Available at: <https://fdc.nal.usda.gov/fdc-app.html#/food-details/781089/nutrients> [Accessed 10 August 2020].

    [4] Nakamura M, Nagahata T, Miura A, Okada E, Shibata Y, Ojima T. Association between Dietary Intake and Autistic Traits in Japanese Working Adults: Findings from the Eating Habit and Well-Being Study. Nutrients. 2019;11(12)

    [5] Hirokawa K, Kimura T, Ikehara S, et al. Associations Between Broader Autism Phenotype and Dietary Intake: A Cross-Sectional Study (Japan Environment & Children's Study). J Autism Dev Disord. 2020;50(8):2698-2709.

    [6] Lahvis GP. What California sea lions exposed to domoic acid might teach us about autism: lessons for predictive and preventive medicine. EPMA J. 2017;8(3):229-235.

    [7] Rahbar MH, Samms-vaughan M, Dickerson AS, et al. Role of fruits, grains, and seafood consumption in blood cadmium concentrations of Jamaican children with and without Autism Spectrum Disorder. Res Autism Spectr Disord. 2014;8(9):1134-1145.

    [8] Vecchione R, Vigna C, Whitman C, et al. The Association Between Maternal Prenatal Fish Intake and Child Autism-Related Traits in the EARLI and HOME Studies. J Autism Dev Disord. 2020;

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