How do they get fish oil for vitamins? The complete guide to sourcing and processing

January 1, 2026 •

3 min read

Over 70% of omega-3 supplements are sourced from small, oily fish like anchovies, sardines, and mackerel. The process to get fish oil for vitamins involves a series of complex steps, including meticulous sourcing, extraction, and advanced purification methods to ensure a safe and potent final product.

Quick Summary

The journey of fish oil for supplements starts with sourcing small, oily fish, followed by extraction, refining, and rigorous purification to remove impurities. Advanced techniques like molecular distillation are crucial for achieving the high purity needed for human consumption.

Key Points

Sourcing: Fish oil primarily comes from small, oily, cold-water fish like anchovies, sardines, and mackerel, which are lower on the food chain and less likely to accumulate high levels of contaminants.
Extraction: The oil is extracted from the fish's tissues through a process involving cooking, mechanical pressing, and centrifugation, separating the crude oil from other fish components.
Purification: Crude oil is refined using multiple steps, including degumming, neutralization, bleaching, and deodorization to remove impurities, free fatty acids, and odors.
Molecular Distillation: This advanced technology is critical for producing high-quality fish oil, using a vacuum to remove heavy metals and other environmental contaminants while concentrating omega-3s.
Sustainability: Reputable manufacturers ensure sustainability by sourcing from responsibly managed fisheries and obtaining certifications like Friend of the Sea or Marine Stewardship Council.
Bioavailability: Fish oil can be sold as ethyl esters or, for better absorption, undergo re-esterification to return to its natural triglyceride form.
Quality Control: Third-party testing by organizations like IFOS is vital to confirm the product's purity, potency, and freshness.

From Ocean to Capsule: A Look at Fish Oil Sourcing

Fish oil production begins long before the oil is bottled. The journey from the ocean to a vitamin begins with careful selection of the raw material. Unlike larger, predatory fish which can accumulate higher levels of contaminants like mercury, most manufacturers utilize small, oily fish that are lower on the food chain.

Key Fish Species for Fish Oil Production

Anchovies and Sardines: These small, fast-growing fish are a primary source for fish oil due to their high omega-3 content and low contaminant levels.
Mackerel and Herring: Also small, cold-water fish, they are another abundant and sustainable source of omega-3 fatty acids.
By-products: A significant amount of fish oil is also derived from the leftover trimmings and by-products of the seafood processing industry, promoting resource efficiency.

The Extraction and Refining Process

Once the fish are harvested, they are processed quickly to preserve freshness and minimize oxidation. The extraction process typically involves a method called wet rendering, though other advanced techniques exist.

Step-by-Step Production

Cooking: Fish are cooked using steam, which helps break down the tissue and release the oil and water content.
Pressing: The cooked mixture is then pressed to separate the liquid, which is a mixture of oil and water, from the solid fish meal.
Separation: The oil and water are then separated through centrifugation. This step removes solid particles and isolates the crude fish oil.

Advanced Refining for Purity and Quality

The crude fish oil is not yet ready for consumption. It undergoes several refining steps to remove impurities, improve quality, and concentrate the omega-3 content.

Degumming and Neutralization: This stage removes phospholipids and free fatty acids that can cause rancidity.
Bleaching and Deodorization: Filters remove pigments, and steam distillation removes volatile compounds that cause the strong fishy odor and taste.
Molecular Distillation: This is a crucial step for producing high-purity fish oil. Performed under a vacuum with precise temperatures, it removes environmental contaminants like heavy metals (mercury, lead) and dioxins. This process also concentrates the levels of EPA and DHA.

The Importance of Sustainability

The demand for fish oil has raised concerns about sustainability and overfishing. Reputable manufacturers address this by adhering to international standards and certifications.

Friend of the Sea: This certification ensures that the fish are sourced from not overexploited stocks, with minimal impact on marine ecosystems.
Marine Stewardship Council (MSC): This logo confirms that the product comes from a certified sustainable fishery.

Bioavailability: Ethyl Esters vs. Triglycerides

After purification, some manufacturers perform an additional step called re-esterification to convert the oil back into its natural triglyceride form for better absorption. This leads to different product types.


Feature	Ethyl Ester (EE)	Re-Esterified Triglyceride (rTG)
Form	Semi-synthetic fatty acid	Re-created natural form
Absorption	Good, but not as efficient as rTG	Superior absorption and bioavailability
Concentration	Typically very high due to molecular distillation	Also high, maintaining the concentrated omega-3 levels
Cost	Generally less expensive to produce	More expensive due to the additional enzymatic process
Purity	Very high purity, especially after molecular distillation	Very high purity, with contaminants removed during prior steps

What to Look for in a High-Quality Supplement

Consumers can make informed choices by looking for specific markers on product labels:

Third-Party Testing: Certifications from organizations like the International Fish Oil Standards (IFOS) program ensure the product's purity, potency, and freshness.
Concentration Levels: Check the label for the specific amounts of EPA and DHA per serving.
Source and Sustainability: Look for sustainable sourcing certifications like Friend of the Sea or MSC.
Freshness Indicators: High-quality manufacturers often test for oxidation levels (TOTOX value) and use nitrogen flushing to prevent spoilage and fishy burps.

Conclusion: The Final Product

The journey of fish oil from the ocean to a vitamin is a testament to modern nutritional science and advanced manufacturing. What begins as a natural resource from small, oily fish or seafood by-products is meticulously purified and concentrated using methods like molecular distillation. The final product, whether in the ethyl ester or more bioavailable re-esterified triglyceride form, represents a carefully crafted supplement that delivers essential omega-3 fatty acids while ensuring safety and freshness. For consumers, understanding this process allows for a more informed choice, prioritizing both personal health and environmental sustainability. For more information, the Global Organization for EPA and DHA Omega-3s (GOED) is an authoritative source on the industry and standards.

Frequently Asked Questions

Most manufacturers use small, oily, cold-water fish such as anchovies, sardines, and mackerel. These fish are lower on the food chain, which means they have lower levels of contaminants like mercury compared to larger predatory fish.

The most common method is wet rendering. This involves cooking the fish with steam to release the oil, pressing the cooked fish to separate the liquid, and then using a centrifuge to separate the oil from the water.

High-quality fish oil supplements are rigorously purified to remove heavy metals and environmental toxins. A process called molecular distillation is used specifically for this purpose, and third-party testing verifies the product's purity.

Molecular distillation is an advanced purification technique that uses a vacuum and low heat to separate and remove impurities and contaminants from the fish oil. It also helps concentrate the beneficial omega-3 fatty acids.

Yes, choosing sustainably sourced fish oil is important for environmental protection. It ensures that the fish are harvested from healthy populations using methods that minimize harm to marine ecosystems and prevent overfishing.

Fish oil is commonly available as ethyl esters (EE) or re-esterified triglycerides (rTG). While EE is concentrated and pure, the rTG form is molecularly closer to how omega-3s occur in nature and is considered to have better bioavailability and absorption.

Look for third-party testing certifications, such as the IFOS seal, which guarantees purity and quality. Also, check the specific amounts of EPA and DHA per serving, and look for sustainability certifications like Friend of the Sea.

No, fish oil supplements can vary significantly in quality, purity, and concentration. Cheaper brands may not undergo the same level of purification and might contain contaminants, while premium brands use advanced distillation and have high purity standards.

Yes, oil derived from the trimmings and by-products of the seafood processing industry is often of excellent nutritional quality. It also promotes efficiency by utilizing a resource that would otherwise be discarded, contributing to sustainability.

A fishy aftertaste or 'fish burps' can be an indicator of oxidation, or rancidity, in the oil. High-quality fish oil is processed to minimize oxidation, and some manufacturers use nitrogen flushing to preserve freshness and prevent this issue.