Is omega-3 made from shellfish? Understanding diverse sources and allergy considerations

November 5, 2025 •

4 min read

While it is a common misconception that all omega-3 comes from fish, some varieties and supplements are derived from marine crustaceans like krill, which are a type of shellfish. Understanding the origin is crucial, especially for those with allergies, and answers the question: Is omega-3 made from shellfish?

Quick Summary

Not all omega-3 is sourced from shellfish; while krill oil is, many other marine and plant-based supplements provide this nutrient. Purification processes may reduce allergens, but alternatives like algae oil exist for those with allergies.

Key Points

Diverse Origins: Omega-3s come from various sources, including fatty fish, krill (a type of shellfish), and plants like flaxseeds and algae.
Krill Oil is Shellfish-Based: Krill oil supplements are extracted directly from Antarctic krill, a small crustacean, making them a definite no for those with shellfish allergies.
Algae is the Root Source: Fish and krill get their EPA and DHA omega-3s by consuming microalgae, the true primary producer of these fatty acids.
Algae Oil for Allergies: For individuals with shellfish or fish allergies, or those following a vegan diet, algae oil supplements offer a safe and direct source of EPA and DHA.
Purification Limits Risk, but Doesn't Erase It: While fish oil undergoes purification to remove allergenic proteins, trace amounts or cross-contamination are possible, so caution is warranted for severe allergies.
Plant-Based ALA: Plant sources like flaxseed and walnuts provide ALA omega-3, but the body's conversion to the more potent EPA and DHA is inefficient.

What are omega-3s and where do they originate?

Omega-3 fatty acids are a group of essential polyunsaturated fats that are vital for numerous functions in the human body, including brain, eye, and heart health. The three primary types are alpha-linolenic acid (ALA), eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA).

ALA (Alpha-Linolenic Acid): This is found mainly in plant-based foods such as walnuts, flaxseeds, chia seeds, and certain oils like canola and soybean oil. The human body can convert ALA into EPA and DHA, but the conversion rate is very low, making direct intake of EPA and DHA more efficient.
EPA and DHA: These are the more potent forms of omega-3 and are found predominantly in marine sources. However, it is a common misconception that fish produce EPA and DHA themselves. In fact, these fatty acids originate from microalgae at the bottom of the marine food chain. Fish and other marine organisms, including certain shellfish, accumulate these nutrients by consuming the algae or smaller organisms that have eaten the algae.

The role of shellfish as an omega-3 source

Certain shellfish do contain omega-3 fatty acids, but generally in lower concentrations than fatty, cold-water fish. For example, mussels, oysters, and crab are known to provide some omega-3s. However, the most notable link between shellfish and omega-3 supplements is through krill.

Krill are tiny, shrimp-like marine crustaceans that are a key food source in the ocean. Krill oil is extracted from these crustaceans and sold as a dietary supplement. Therefore, if a supplement contains krill oil, it is directly sourced from a type of shellfish. Krill oil contains EPA and DHA, with the fatty acids bound to phospholipids, which some research suggests may be more bioavailable than the triglycerides in standard fish oil.

Can omega-3 supplements contain shellfish allergens?

This is a critical concern for individuals with shellfish allergies. The production of omega-3 supplements involves extensive purification processes to remove impurities, including proteins that cause allergic reactions. For fish oil, the protein allergen is typically removed. However, with krill oil, the source is inherently shellfish.

While purification aims to remove all allergenic proteins, there is no absolute guarantee that trace amounts won't remain, especially due to potential cross-contamination in manufacturing facilities. The American Academy of Allergy, Asthma & Immunology (AAAAI) states that for people with shellfish allergies who tolerate finned fish, a fish oil supplement is unlikely to cause a reaction, but the risk cannot be fully eliminated. For those with a severe shellfish allergy, extreme caution is advised with krill oil and even fish oil from factories that also process shellfish. Many supplement labels carry warnings regarding fish or shellfish allergies.

Sustainable and allergy-safe omega-3 alternatives

Fortunately, for those with shellfish or fish allergies, or individuals seeking vegetarian or vegan options, several excellent alternative sources are available.

Algae Oil: As the original source of EPA and DHA, algae oil provides a direct, plant-based route to these essential fatty acids. Algal oil is grown in controlled, indoor fermentation systems, which eliminates the risk of contaminants like mercury and provides a sustainable option for the growing omega-3 demand. This makes it a perfect and safe choice for those with marine allergies or following a vegan diet.
ALA-rich plant foods: Flaxseed, chia seeds, walnuts, and hemp seeds are all fantastic sources of ALA omega-3. While the body's conversion of ALA to EPA and DHA is inefficient, a diet rich in these foods can still contribute significantly to overall omega-3 intake.

Comparison of Omega-3 Supplement Sources


Feature	Fish Oil	Krill Oil	Algal Oil
Primary Source	Fatty fish tissue (e.g., salmon, anchovies)	Antarctic krill (small crustaceans/shellfish)	Microalgae
Omega-3 Type	EPA and DHA, mainly as triglycerides	EPA and DHA, bound to phospholipids	EPA and DHA (often higher DHA)
Allergy Risk	Low for shellfish allergy, but potential for fish protein traces	Direct risk for those with shellfish allergies	Safe for both fish and shellfish allergies
Sustainability	Variable, potential overfishing concerns	Carefully regulated quotas, MSC-certified	Highly sustainable, grown in controlled systems
Contaminant Risk	Requires extensive purification to remove heavy metals	Low, from pristine Antarctic waters	Very low, produced in controlled environments
Best For	General population seeking EPA/DHA	General population seeking bioavailable EPA/DHA	Vegetarians/vegans, or those with marine allergies

How supplement processing removes allergens

Commercial omega-3 oil, especially fish oil, undergoes sophisticated processing to ensure safety and purity. Molecular distillation is a key step used to remove impurities like heavy metals, dioxins, and other contaminants. This high-vacuum, low-heat process also helps remove saturated fats and undesirable organic compounds. While this process is effective at concentrating the desired fatty acids and removing many impurities, the critical concern for allergy sufferers is the presence of proteins, as an allergy is a reaction to a protein. For fish oil, purification typically removes these allergenic proteins. However, manufacturers of krill oil start with a shellfish source and must specifically ensure allergenic proteins are completely eliminated, a guarantee that cannot always be 100% assured due to manufacturing complexities.

Conclusion

So, is omega-3 made from shellfish? The answer is nuanced. While many popular omega-3 supplements are sourced from fish, krill oil is explicitly derived from a type of shellfish. This has significant implications for individuals with shellfish allergies, as it poses a direct risk, even with extensive purification. Fortunately, the nutritional landscape offers fantastic and safe alternatives. The most compelling choice for those with marine allergies or dietary restrictions is algae oil, which provides the same beneficial EPA and DHA fatty acids from a plant-based, sustainably sourced origin. Consumers should always check product labels and, if they have a severe allergy, consult a healthcare provider and consider a guaranteed shellfish-free option like algae oil. To further explore the importance of omega-3s, visit the National Institutes of Health's fact sheet on omega-3 fatty acids.

Frequently Asked Questions

No, krill oil is extracted from krill, which is a type of marine crustacean and therefore contains shellfish proteins. Individuals with shellfish allergies should avoid krill oil.

While fish oil supplements typically undergo a purification process to remove allergenic proteins, trace amounts may still be present due to potential cross-contamination during manufacturing. Consulting an allergist is recommended, and an algae-based alternative is the safest choice.

Algae oil is the best supplement for vegans and vegetarians as it provides a direct, plant-based source of the essential EPA and DHA fatty acids. It is sustainably grown and free of marine allergens.

Most plant foods, like flaxseeds and walnuts, contain ALA omega-3, which the body must convert to EPA and DHA. The only plant-based source that provides pre-formed EPA and DHA is algae.

Commercial omega-3 supplements are purified using processes like molecular distillation, which uses low-temperature, high-vacuum methods to remove heavy metals and other contaminants, concentrating the omega-3 fatty acids.

For severe allergies, the safest option is to avoid all marine-derived products, including fish oil and krill oil, to eliminate the risk of accidental exposure to shellfish allergens. Algae oil is a secure and effective alternative.

No, algae oil can be a highly concentrated and potent source of EPA and DHA. Some algal oils are naturally higher in DHA, and the controlled production methods can yield a highly targeted and pure product.