Can You Remove Mercury from Fish Oil? The Manufacturing Process Explained

October 24, 2025 •

4 min read

According to research, many people are concerned about heavy metal contamination, including mercury, found in seafood. The reassuring news for supplement users is that modern manufacturing has a definitive answer to the question: Can you remove mercury from fish oil? The process ensures high-quality supplements are virtually free of this toxin.

Quick Summary

This article explains how fish oil manufacturers use advanced techniques, such as molecular distillation, to strip away mercury and other heavy metals. It also covers how to identify purified, high-quality supplements through third-party certifications like IFOS.

Key Points

Mercury is Removed by Distillation: Reputable manufacturers use a process called molecular distillation to effectively remove heavy metals like mercury from fish oil.
Vacuum Distillation is Key: Molecular distillation operates under a vacuum and at low temperatures, which allows for the separation of impurities without damaging the delicate omega-3 fatty acids.
Third-Party Certification Ensures Purity: Certifications like the 5-star rating from IFOS confirm that a fish oil product has been tested for contaminants and meets high purity standards.
Fish Oil Supplements Can Be Purer Than Some Fish: Due to the purification process, high-quality fish oil supplements often contain negligible levels of mercury, sometimes less than what is found in larger, unpurified fish.
Choose the Right Products: To ensure safety, look for supplements derived from smaller fish (like sardines and anchovies) that are lower on the food chain and display a third-party purity certification.
Purity Prevents Health Risks: Purified fish oil allows consumers to safely enjoy the cardiovascular, cognitive, and anti-inflammatory benefits of omega-3s without the risk of mercury toxicity.

The Concern with Mercury in Fish

Fish are a vital part of a healthy diet, rich in essential omega-3 fatty acids like EPA and DHA. However, pollution has led to the accumulation of heavy metals, most notably mercury, in marine ecosystems. Mercury is a neurotoxin that can bioaccumulate, meaning its concentration increases as it moves up the food chain. This means that large, predatory fish, such as shark, swordfish, and some tuna species, tend to have the highest mercury levels. This poses a particular risk to sensitive populations, including pregnant women and young children, whose developing nervous systems are most vulnerable. Concerns about mercury can sometimes deter people from consuming fish or fish oil, leading them to miss out on the valuable omega-3 fatty acids.

How Mercury is Removed from Fish Oil

For fish oil supplements, the purification process is a key differentiator from whole fish consumption. The main technology used by reputable manufacturers to address the issue of mercury is molecular distillation. This is a highly effective, industrial-scale process that separates contaminants from the beneficial oils.

The Molecular Distillation Process

Molecular distillation is a form of short-path vacuum distillation. Here's a step-by-step breakdown of how it works:

Initial Extraction: The raw fish oil is first extracted from the tissues of omega-3 rich fish, such as anchovies, sardines, and mackerel, which naturally have lower mercury levels.
Esterification: Before distillation, the triglycerides in the oil are often converted into ethyl esters, which allows for easier separation during the process.
Vacuum Application: The oil is placed in a still and subjected to an extreme vacuum. This dramatically lowers the boiling points of the oil's components.
Precise Heating: The oil is then heated gently and precisely. Under the vacuum, the various molecules evaporate and condense at different, lower temperatures based on their molecular weights and boiling points.
Separation: Since mercury and other heavy metals have higher molecular weights and different boiling points than the omega-3 fatty acids, they are left behind in the distillation pot. This leaves a pure, concentrated omega-3 product.
Re-esterification (for some brands): Some manufacturers take an extra step to convert the purified ethyl esters back into a more natural, re-esterified triglyceride (rTG) form for better absorption.

Other Purification and Quality Control Steps

Filtration: After extraction, the oil is often filtered to remove solid impurities.
Bleaching: A bleaching step can remove coloring particles and residual contaminants.
Protection Against Oxidation: To prevent rancidity, modern processes use inert gas (like nitrogen) to minimize oxygen exposure during distillation and storage. Antioxidants like vitamin E are also often added.

Ensuring Purity: The Role of Third-Party Testing

For consumers, the best assurance of a mercury-free fish oil supplement is third-party testing. Reputable companies submit their products for independent analysis by organizations that specialize in fish oil standards.

International Fish Oil Standards (IFOS)

The most respected of these programs is the International Fish Oil Standards (IFOS). IFOS rates fish oil products based on strict criteria, evaluating them for purity, potency, and freshness. A 5-star IFOS rating confirms that a product has met or exceeded international standards for:

Purity: Levels of heavy metals (mercury, lead, cadmium) and environmental toxins (PCBs, dioxins) are below stringent limits.
Potency: The concentration of EPA and DHA matches or exceeds the label claim.
Freshness: Total oxidation levels are low, indicating the oil is fresh and not rancid.

Consumers can look for the IFOS seal on product packaging or search the IFOS website to verify the test results for a specific batch.

Supplements vs. Whole Fish: The Purity and Potency Debate

While a diet of whole fish is a fantastic source of omega-3s, fish oil supplements offer a compelling alternative, particularly regarding contaminant exposure and dosage control.


Feature	Purified Fish Oil Supplements	Whole Fish (especially larger species)
Mercury Content	Negligible to non-detectable levels due to molecular distillation and rigorous testing.	Varies significantly depending on the species and size of the fish. Higher in larger, predatory fish.
Omega-3 Concentration	Often highly concentrated to deliver a potent dose in a small capsule or serving.	Variable; some oily fish like salmon and sardines are high, while leaner fish like cod are lower.
Other Contaminants	Tested for and purified of PCBs and dioxins.	May contain other pollutants from the marine environment.
Nutritional Profile	Primarily provides concentrated EPA and DHA.	Offers a broader range of nutrients, including vitamins, minerals, and high-quality protein.

Conclusion

Thanks to modern manufacturing techniques like molecular distillation and stringent third-party testing, reputable brands can indeed remove mercury and other contaminants from fish oil. This results in a purified, high-quality supplement that offers the health benefits of omega-3s without the risk of heavy metal exposure associated with some fish. For consumers concerned about purity, choosing a product verified by an independent organization like IFOS provides the peace of mind that comes with a clean and effective supplement. For more information on purity standards, you can visit the International Fish Oil Standards (IFOS) website.

Frequently Asked Questions

Mercury is removed from fish oil primarily through a process called molecular distillation, which separates contaminants based on their molecular weights and boiling points under a vacuum.

No. While raw fish oil may contain trace amounts of mercury, reputable manufacturers use advanced purification methods, like molecular distillation, to ensure their finished products contain negligible to non-detectable levels.

Molecular distillation is a high-vacuum, low-temperature purification process used to remove heavy metals, PCBs, and other impurities from fish oil. It works by exploiting the different boiling points of the compounds.

For those concerned about mercury, purified fish oil can be a safer alternative. The purification process removes heavy metals, whereas mercury is found within the muscle tissue of some fish and cannot be cooked out.

The most reliable way is to look for third-party certifications on the product label, such as a 5-star rating from the International Fish Oil Standards (IFOS), which tests for purity, potency, and freshness.

Yes, manufacturers often use smaller, shorter-lived fish like sardines and anchovies because they are lower on the food chain and naturally accumulate less mercury than larger predatory fish.

No, it is not possible to remove mercury from fish oil at home. The process requires specialized industrial equipment and controlled conditions to effectively separate the heavy metals.