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Pile of fish oil capsules of high quality

Finding A High Quality Fish Oil

Not all fish oil is the same in terms of nutritional content or purity. Dr. Scott Fogle, ND, explains how to assess a fish oil supplement’s quality, certificate analysis, and testing protocols to select quality fish oil with a safe, Five-Star rating.

Scientifically reviewed by Dr. Gary Gonzalez, MD, in August 2023. Written by: Dr. Scott Fogle, ND, Physician.

Finding A High Quality Fish Oil  

Q: How can I tell if I’m getting a high-quality fish oil product since there are so many fish oil products on the market?

A: In the wake of recent news that some dietary supplement products may not contain what they say on their labels, consumers are becoming more cautious and concerned about the products they spend their money on. They want to know if they are getting what it says on the label. They also want to know if there are any contaminates or toxins in the product. Equally important, consumers do not want to be misled into using a product that lacks the potency necessary to meet their health needs. Thus, there is a growing focus by consumers on potency and purity, now more than ever.

Request A Certificate Of Analysis

To ensure that a product meets its label claims, an array of analytical equipment is required to verify ingredient identity and potency. Unfortunately, unless you have your own analytical lab in your basement, there is no way to conveniently perform the testing necessary to verify these claims. Many companies tout their purity and potency with claims in their marketing literature, but how can you verify those claims? Fortunately, there are several ways that you can obtain key information about product quality to make an informed purchasing decision.

The best way is to request a certificate of analysis (COA) from the company. If a company cannot, or will not, provide you with a COA for the product, this should raise a big red flag. Once the company provides a certificate of analysis, look carefully at the COA you received. Is it a representative COA or is it a lot-specific COA? Representative COAs generally reflect the best COA that was obtained for all of the product’s various batches or lots (production runs). The company picks the best COA to represent the product and this is what they send. Unfortunately, product quality often changes between production runs, which means that although a representative COA is a good start, it does not provide the lot-specific information necessary to determine how pure and potent the specific bottle you purchased is. Obtaining a lot-specific COA that matches the exact lot number for the product you have in your hand is much more meaningful. A company that can provide you with a lot-specific COA is a top-tiered company with a focus and proficiency in creating and delivering high quality products to its customers. A lot of effort is needed in order to provide lot specific COAs so it also typically means these companies have their own in-house quality control and quality assurance team constantly checking their products and performing quality audits at their manufacturing facilities.

Q: So what does a COA tell me?

A: It tells you a lot about product potency and purity. It even contains other important information like disintegration times.

Finding A High Quality Fish Oil  

Typically, a COA starts off with a section that identifies the product. It has a description section that includes details such as capsule size, fill color, lot number, and manufacture date.

The next section contains information regarding potency testing, often called the “assay section.” The claims made on the product label, including ingredient identity and strength, are what will be tested for and listed in the assay section of the COA. It contains a list of specific markers (ingredients or standardized constituents), such as EPA and DHA for fish oils, and their respective strengths as verified through analytic techniques like high performance liquid chromatography or gas chromatography–mass spectrometry (HPLC or GC/MS).

At a minimum, each product should meet its label claims for identity and potency. What few people realize, however, is that premium-grade products are often formulated with extra potency (overage). Top quality companies typically err on the side of providing extra potency to ensure they always meet or exceed their label claim and to ensure they can still meet label claim at end of the “best by” date as well. This means that products from top companies will often have an overage that would look like 117%, meaning it has 17% over the amount claimed on the label. So you can actually be getting more than you paid for, something that doesn’t happen often nowadays!

The assay section will also have a disintegration section that tells you how long it takes to dissolve. The solutions used in the testing can be water with a pH around 7, a buffered solution with a pH of 6, or a solution that stimulates gastric acid with a much lower pH. The solution used in the test is determined by United States Pharmacopeial guidelines for the supplement being tested. Generally, quality companies set a disintegration time limit of <30 minutes for optimal effectiveness. This means in less than 30 minutes, the capsule, tablet, or softgel should degrade enough to release its contents. The disintegration test is making sure the capsule, tablet, or softgel will release its contents so that they can be utilized by the body and exert their effects. Note that the disintegration time does not mean all the material will dissolve in the solution; that is a common misconception. The purpose of the test is to ensure that the capsule, tablet, or softgel will release its beneficial contents in that time. You don’t want capsules or tablets passing through your system without releasing their contents.

The next section of a COA is microbiological testing because no one wants mold, yeast, or bacteria growing in their products. The first component listed in this section of the COA is the total plate count. This is a very important test since it looks at the total growth of all the microbes that can grow on an agar plate (a Petri dish containing food for them to grow). Additionally, the product is tested separately for total yeast and mold to assess growth of these particular organisms. Finally, agar plates are tested for three bacterial species known to be of greatest concern: E. coli, Salmonella, and Staphylococcus aureus. If agar plates show any growth of these harmful bacteria, the product is rejected.

The final section of a COA typically contains heavy metal testing results. There are four metals to be concerned about in the world today and it is growing ever harder to avoid them. These heavy metals—arsenic, cadmium, mercury, and lead—are tested for and reported, and if any of these are above a strict threshold, then the product is rejected. Unfortunately our planet is polluted far more than most people realize. Our soil and water are ever increasing in these persistent toxins and not much is being done about it. Thus it is important to test for arsenic, cadmium, mercury, and lead in your supplements.

Testing For Toxins

Finding A High Quality Fish Oil  

Q: This sounds great! But with fish oils don’t you have to worry about even more toxins than most supplements?

A: Yes, that is correct. Fish oils have other components that can be tested and the best dietary supplement companies spend the extra money to get them tested by the International Fish Oil Standards (IFOS) program. This is an independent laboratory that specializes in testing and rating fish oils. They provide a very important consumer function in doing this specialized testing. Consumers should look for a fish oil that has a Five-Star rating given by IFOS. If they aren’t tested by IFOS, you simply don’t know what you are getting when you take that fish oil supplement.

IFOS provides a star for achieving each of the following criteria: A first star is awarded for passing all the stringent testing categories set by three influential organizations—the Council for Responsible Nutrition, Global Organization for EPA and DHA Omega-3, and the World Health Organization. Passing all those is no easy task! A second star is awarded if the omega-3 concentrations exceed 60% of the fish oil contained in the formula. This star helps weed out the products that don’t have the higher concentrations of the beneficial components of fish oil, the omega-3s. If you are buying a generic fish oil product, it may not get a star in this important category. Three more stars are awarded for categories dealing with three toxic markers. After all, we take fish oils to obtain their numerous health benefits, not to add more toxins into our bodies.

One marker IFOS looks for is overall oxidation of the fish oil. Fish oil is beneficial because it contains numerous double bonds in its hydrocarbon chain, making it “polyunsaturated.” Since fish oils are rich in these polyunsaturated fatty acids, fish oils are much more susceptible to oxidation than other oils, like olive or coconut. These wonderful double bonds enable fish oil’s amazing biological effectiveness, but it comes at a cost. Those double bonds are the same places were oxidation can attack. If that happens, the oil will become rancid and is no longer beneficial. Thus, it is more important to test for oxidation in fish oil than other oils that don’t have as many double bonds. IFOS does this by testing not just total oxidation of the oil but also by looking at specific levels of peroxide and anisidine in the fish oil as individual markers of oxidation. As anisidine levels increase in an oil, so does its rancid smell, a marker of its degree of oxidation.

Another important, but less well known test, is the total acid value of the oil. When free fatty acids are cleaved off their parent molecules (triglycerides or phospholipids), this process will increase the total acid value of the oil. Guess what is great at initiating this cleavage of free fatty acids? Microorganisms! Thus, an increase in the total acid level generally indicates an excess of microbes, which is not what you want to find in your fish oil.

Testing For Pollutants

Q: What about PCBs? I’ve heard they can be a concern in fish oil products.

A: Yes, another common concern amongst consumers is whether or not their fish oil contains persistent organic pollutants (POPs), such as polychlorinated biphenyls (PCBs). Human exposure to these contaminants has been associated with a wide range of toxic effects including endocrine disruption, immune suppression, and neurological changes. These contaminants are industrial byproducts, so although not naturally present in fish oil, they can find their way into the water supply from industrial pollution, and the fish become contaminated. POPs tend to accumulate in the fatty tissue of fish, so it is particularly important to test for them in fish oil. Fortunately, IFOS tests fish oils for common POPs including total PCBs, dioxins and furans, and dioxin-like PCBs to ensure that levels fall below strict limits. Ensuring fish oil is free of these toxins is critical when evaluating fish oil quality and safety.

The final category for IFOS testing is heavy metal testing. It looks at the same four toxic metals found on a certificate of analysis (COA). It checks levels of mercury, lead, arsenic, and cadmium. It must pass the stringent standards for these toxic metals as described by the Council for Responsible Nutrition as well as the Global Organization for EPA and DHA Omega-3s.

Testing For Radiation

Finding A High Quality Fish Oil  

Q: Is radiation a concern given past events like the Fukushima disaster?

A: In 2015, IFOS also added a new category to its extensive testing menu, this one for radiation. Concern about the dangers of radiation in fish oils, primarily from recent events like the Fukushima Daiichi nuclear power plant disaster of 2011, have persisted among consumers. To help ease consumer concern regarding radiation, IFOS took the initiative to start testing fish oil for radiation. IFOS will now test fish oil samples against more stringent criteria than the guidelines set by the FDA, Health Canada, and CODEX. Fortunately, so far the testing is not showing radiation to be a concern in most fish oils, but IFOS is remaining vigilant to make sure.


Only when a product can pass ALL of the categories mentioned previously, will it achieve a Five-Star rating. Thus, consumers would be wise to make sure the fish oil they are taking is one that has a lot-specific COA and has also been awarded a Five-Star rating by IFOS. This is a powerful combination of quality testing to help assure the potency and purity of a fish oil product.

If you have any questions on the scientific content of this article, please call a Life Extension® Wellness Specialist at 1-866-864-3027.

Dr. Scott Fogle is the Director of Clinical Information and Laboratory Services at Life Extension®, where he oversees scientific and medical information as well as its laboratory division.