What kind of fish do they make fish oil from?

December 24, 2025 •

4 min read

According to the National Institutes of Health, fish oil is extracted from oily fish that are rich in the omega-3 fatty acids EPA and DHA. When answering the question, "What kind of fish do they make fish oil from?", the answer typically points to small, fatty, cold-water varieties that accumulate these beneficial fats by consuming microalgae.

Quick Summary

Fish oil is derived from small, oily fish such as sardines, anchovies, mackerel, and herring, which are excellent sources of omega-3s. Larger fish like salmon and tuna also provide these healthy fats, though some may carry higher mercury risks depending on their position in the food chain. Purification methods remove most contaminants.

Key Points

Small, Oily Fish: Most fish oil is sourced from small, oily, cold-water fish like anchovies, sardines, and herring, which are lower in mercury due to their position in the food chain.
Larger Fish Sources: Fish oil can also come from larger species such as salmon and tuna, though the risk of mercury contamination is higher with predatory fish.
Cod Liver vs. Fish Oil: Cod liver oil, sourced specifically from cod livers, contains vitamins A and D in addition to omega-3s, unlike standard fish oil from body tissues.
Source of Omega-3s: Fish do not produce omega-3s themselves but acquire them by eating microalgae, which are the primary producers of EPA and DHA.
Purification Process: Most high-quality fish oil is molecularly distilled to remove environmental contaminants like mercury and PCBs, ensuring a safe and pure product.
Sustainability Matters: Consumers can choose sustainably sourced fish oil or vegan alternatives like algae oil to minimize environmental impact.

The Primary Sources: Small, Oily Fish

The most common and often most sustainable sources for commercial fish oil are small, oily, cold-water fish. These species are lower on the food chain, meaning they have a shorter lifespan and less exposure to environmental toxins like mercury that can accumulate over time. The primary types of small fish used include:

Anchovies: Tiny fish often found in the Mediterranean, anchovies are a very common source for fish oil supplements. Their small size and abundance make them a sustainable choice, and they yield oil with a high omega-3 concentration.
Sardines: These small, bony fish are packed with omega-3s and are frequently used in both canned food and supplement production. Like anchovies, they are low on the food chain, which keeps their mercury levels minimal.
Herring: A key player in many marine ecosystems, herring are another excellent source of omega-3s. They are widely harvested and provide a nutrient-rich oil.
Mackerel: Both Atlantic and Spanish mackerel are significant sources of omega-3s. Smaller mackerel varieties are often preferred for fish oil to minimize potential exposure to contaminants.

Larger Fish Sources and the Mercury Factor

While smaller fish are often the cornerstone of high-purity fish oil, larger fish are also utilized, though with greater consideration for contaminants. These fish are higher up the food chain, which can lead to biomagnification of toxins.

Salmon: A popular food source of omega-3s, salmon is also used for fish oil. It is a rich source of both EPA and DHA. The oil yield can vary based on whether the salmon is wild-caught or farmed, as farmed fish are often fed supplemental omega-3s.
Tuna: Oil from certain tuna species, particularly canned light tuna, can be a source of omega-3s. However, larger tuna species like bigeye tuna can have higher mercury levels, and supplements derived from them should undergo thorough purification.
Pollock: The oil from pollock, a common white fish, is another source for omega-3 supplements.

Beyond Body Oil: Cod Liver Oil

It's important to distinguish between standard fish oil and cod liver oil. While standard fish oil is typically extracted from the fatty body tissues of various oily fish, cod liver oil is, as the name suggests, specifically derived from the liver of cod. This means that in addition to EPA and DHA, cod liver oil is also a natural source of vitamins A and D. However, excessive intake can lead to dangerously high levels of vitamin A, so modern fish oil supplements are often purified to remove these vitamins.

Comparison of Common Fish Oil Sources

To better understand the differences, consider this comparison of typical fish oil sources:


Feature	Sardines/Anchovies	Salmon	Tuna	Cod	Mackerel (King)
Typical Size	Small	Large	Very large	Large	Very large
Source for Oil	Body tissues	Body tissues	Body tissues	Liver	Body tissues
Primary Omega-3s	EPA > DHA	DHA > EPA	EPA & DHA	EPA & DHA	EPA & DHA
Mercury Risk	Very Low	Low to Moderate	High (Bigeye)	Low (liver)	High
Sustainability	High (Abundant)	Varies (Wild vs. Farmed)	Concern (Overfishing)	Varies	High (Contamination Risk)

The Journey from Ocean to Capsule

After fishing, the process of creating fish oil involves several key steps to ensure a high-quality, pure product. The fish are cooked, and the oil and water are pressed out. This liquid mixture is then separated using a centrifuge. To ensure safety, especially from larger fish, the oil undergoes a process called molecular distillation. This purification process, performed under a vacuum, effectively removes fat-soluble environmental contaminants, such as PCBs and heavy metals like mercury, to meet strict purity standards. This results in a cleaner, safer oil, and the levels of contaminants are often stated in parts per billion or trillion.

Sustainable Sourcing and Purity

For conscientious consumers, the source and purity of fish oil are crucial. Reputable manufacturers use sustainably sourced fish and provide third-party testing to verify the purity and potency of their products. This ensures that the oil is not only rich in beneficial omega-3s but also free from harmful contaminants. For those seeking alternatives, algae oil provides a plant-based source of EPA and DHA, directly mimicking the original source of these nutrients in the marine food chain.

Conclusion

In conclusion, the answer to what kind of fish they make fish oil from is a variety of small, cold-water, oily fish, such as anchovies, sardines, mackerel, and herring. These are generally favored for their high omega-3 content and lower risk of mercury contamination. Larger fish like salmon and tuna are also used but require more intensive purification. For those concerned about sustainability or potential pollutants, choosing supplements made from smaller fish or opting for purified algae oil are excellent choices. Ultimately, whether from fish or algae, these supplements provide a vital source of omega-3s for those unable to get enough from their diet alone. You can learn more about omega-3 fatty acids and dietary sources from the National Institutes of Health.

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Frequently Asked Questions

The primary source of fish oil for supplements is small, oily, cold-water fish such as anchovies, sardines, and herring. These species are favored for their high omega-3 content and relatively low levels of environmental toxins.

Yes, fish oil can come from different types of fish. For example, standard fish oil comes from the body tissues of oily fish, while cod liver oil is specifically from the liver of cod and contains extra vitamins.

High-quality fish oil supplements are highly purified, typically through a process called molecular distillation, which removes heavy metals like mercury. Therefore, the risk of mercury poisoning from supplements is very low.

Yes, wild-caught and farmed fish can produce oils with differing omega-3 levels. Farmed fish are often fed omega-3-supplemented feed, which affects the oil's final composition.

Fish do not produce omega-3 fatty acids themselves. They obtain them by consuming algae or smaller fish that have eaten algae, which are the original producers of EPA and DHA.

EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid) are both important types of omega-3 fatty acids found in fish oil. While they are both beneficial, their concentrations can vary depending on the fish species. For instance, salmon oil often has more DHA, while oils from herring, mackerel, and anchovies tend to have more EPA.

For those who don't consume fish, vegan alternatives like algae oil are available. Algae are the primary source of EPA and DHA in the marine food chain, and oil from them provides a direct, plant-based source of these essential fatty acids.