Where do we get fish oil from and how is it processed?

December 24, 2025 •

4 min read

Contrary to popular belief, fish do not produce their own omega-3s; they obtain them by consuming microalgae or other fish that do. This process explains why we get fish oil from oily fish species, which accumulate these vital nutrients in their tissues.

Quick Summary

Fish oil is derived from the tissues of fatty fish, which acquire omega-3s from their diet of microalgae. Extraction involves cooking, pressing, and purification to remove toxins, yielding a supplement rich in EPA and DHA.

Key Points

Origin: Fish oil's omega-3s ultimately come from microalgae, which are consumed by fish higher up the food chain.
Primary Source: The main sources for industrial fish oil are small, oily fish like anchovies, sardines, and mackerel, harvested from cold waters.
Extraction Process: Traditional methods involve cooking, pressing, and centrifugation to separate the oil from the fish tissues.
Purification: Modern processing includes molecular distillation, a crucial step that removes heavy metals and other contaminants, ensuring product safety.
Algae Oil: Vegan alternatives derived directly from cultivated microalgae are available and are considered a highly sustainable omega-3 source.
Contaminant-Free: Because algae for oil are grown in controlled environments, algae oil is inherently free of ocean-borne contaminants found in some fish.

The Ultimate Source: Microalgae

While we commonly associate fish with omega-3 fatty acids, the ultimate source of these beneficial compounds is actually marine microalgae. Tiny, single-celled organisms, microalgae produce EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid), which are then consumed by smaller fish. The omega-3s bioaccumulate up the food chain, concentrating in the oily tissues of the larger fish that become the primary commercial source for fish oil supplements. This crucial detail highlights the interconnectedness of marine ecosystems and provides a sustainable alternative via directly cultivated algal oil.

Primary Fish Sources for Oil Production

The majority of commercially available fish oil comes from small, oily fish with high omega-3 content. These species are typically found in cold, nutrient-rich waters.

Common Oily Fish Varieties

Anchovies and Sardines: These small, forage fish are a cornerstone of the fish oil industry. Their small size means they are lower on the food chain, reducing their risk of accumulating high levels of mercury and other contaminants through biomagnification.
Mackerel and Herring: These species are also excellent sources of oil. Like anchovies and sardines, they are often used for large-scale production.
Salmon: Both wild-caught and farmed salmon are rich in omega-3s, although the concentration and type (DHA vs. EPA) can vary. Farmed salmon often receive feed fortified with algae oil to ensure high omega-3 content.
Cod: Specifically, the liver of cod is used to produce cod liver oil, a classic supplement not only rich in omega-3s but also vitamins A and D.
Tuna: Found in lesser amounts than in smaller, oilier fish, tuna can still be a source. Albacore tuna tends to have higher levels of omega-3s.

How Fish Oil is Processed for Supplements

The journey from fish to purified oil involves a series of steps to ensure the final product is safe, stable, and highly concentrated. The most common industrial method is wet rendering.

Cooking: The process begins with cooking the whole, raw fish or fish byproducts (like frames and viscera) in large steam cookers. This heating step breaks down the fish tissue, allowing the oil to be released from the fat depots.
Pressing: The cooked mixture is then pressed to separate the liquid fraction (oil and water) from the solid presscake (fishmeal).
Centrifugation: The liquid mixture is passed through powerful centrifuges that separate the oil from the water based on their different densities.
Refining and Purification: The resulting crude oil contains impurities and needs further processing. Steps include degumming (removes phospholipids), neutralization (removes free fatty acids), bleaching (removes pigments), and deodorization (removes volatile compounds causing fishy odors).
Molecular Distillation: A crucial modern step, molecular distillation involves distilling the oil in a vacuum at low temperatures. This process effectively removes heavy metals, dioxins, and other environmental contaminants while concentrating the beneficial omega-3s.
Encapsulation: The refined and purified oil is then often placed into softgel capsules or bottled with antioxidants like Vitamin E to prevent oxidation.

Fish Oil vs. Algae Oil: A Comparison


Feature	Fish Oil	Algae Oil
Source	Fatty fish like anchovies, sardines, salmon, and mackerel.	Marine microalgae grown in controlled lab environments.
Primary Omega-3s	Contains both EPA and DHA, with proportions varying by fish species.	Can be cultivated to produce DHA, EPA, or a combination, depending on the algae strain.
Risk of Contaminants	Potential for trace heavy metals and pollutants, but these are removed during modern purification processes.	Grown in controlled systems, so it is inherently free from ocean-borne contaminants like mercury.
Sustainability	Relies on fishing, which can contribute to overfishing if not sourced sustainably.	Considered a highly sustainable alternative that does not impact marine ecosystems.
Dietary Suitability	Suitable for those who eat fish and do not have a fish allergy.	Excellent vegan and vegetarian source of EPA and DHA.
Taste/Aftereffects	Can have a fishy aftertaste or cause 'fish burps' if not fresh or high-quality.	Generally has a neutral taste, reducing the likelihood of a fishy aftertaste.

Conclusion: Making an Informed Choice

The question of where we get fish oil from has a multifaceted answer, involving both marine life and advanced processing techniques. While fatty fish are the direct source for most fish oil supplements, the omega-3s within them originate from microalgae. Modern manufacturing, including critical purification steps like molecular distillation, ensures the safety and purity of these products by removing potential contaminants. For those seeking an omega-3 source without relying on fish, algae oil offers an equally effective, sustainable, and vegan-friendly alternative. Understanding these sources and processes empowers consumers to make a choice that aligns with their dietary needs and environmental values. For more details on the industrial manufacturing of fish products, refer to authoritative sources like the FAO: The production of fish meal and oil.

Frequently Asked Questions

Fish oil is primarily made from small, fatty fish like anchovies, sardines, herring, and mackerel. The oil can also come from other oily fish like salmon and the liver of cod.

Yes, high-quality fish oil supplements are safe. During modern processing, the oil undergoes purification methods like molecular distillation, which effectively removes heavy metals, including mercury, and other environmental contaminants.

Cod liver oil is a specific type of fish oil extracted from cod livers, while standard fish oil can be made from various fatty fish. Cod liver oil is also naturally rich in vitamins A and D, in addition to omega-3s.

Yes, algae oil is a popular and effective vegan alternative. It is sourced directly from marine microalgae, the same organisms that produce the omega-3s found in fish.

A fishy aftertaste or 'burp' can indicate that the oil has oxidized or gone rancid. High-quality supplements are processed to minimize oxidation and may be encapsulated with antioxidants to prevent spoilage.

Fish do not produce omega-3s themselves. Instead, they acquire these fatty acids by eating microalgae, which are the primary producers of EPA and DHA in the marine food web.

The sustainability of fish oil production depends on the sourcing. Reputable companies adhere to sustainable fishing practices, but concerns about overfishing persist. Algae oil provides a more sustainable alternative that avoids the use of marine fisheries entirely.