How to Evaluate Fish Oil Quality and Purity
The Omega-3 Supplementation Guide
A blueprint for choosing the right fish oil supplement — filled with specific recommendations, guidelines for interpreting testing data, and dosage protocols.
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In this Institute for Functional Medicine excerpt, Dr. Rhonda Patrick frames omega-3 intake as beneficial and argues that low contaminant exposure should be weighed against the nutritional value of EPA and DHA. Her benefit-risk view does not mean omega-3 negates mercury or PCB toxicity. Contaminant dose, pregnancy, product quality, and individual risk still matter.
Her practical checklist starts with EPA and DHA concentration and chemical form. She prefers triglyceride or re-esterified triglyceride products and says ethyl esters should be taken with a fat-containing meal. Human studies found higher short-term bioavailability for re-esterified triglycerides and much greater ethyl-ester absorption with a high-fat meal. [1] [2]
Next, check oxidation and contaminants. Polyunsaturated fish oil can oxidize, while purification can reduce mercury and persistent pollutants such as PCBs. Product surveys found generally low mercury and lower PCB exposure than fish, but neither purification nor omega-3 content makes contamination harmless. Oxidation findings also vary by product and standard. [3] [4] [5]
Dr. Patrick prefers IFOS because it provides product- and lot-level reports with raw results. She contrasts this with Labdoor’s ranked-product approach. Certification does not prove clinical benefit, and a passing lot does not transfer to every batch. Her final checklist is: verify meaningful EPA and DHA amounts, preferred form and meal instructions, acceptable oxidation, low mercury and PCB results, and a current batch-specific report.
This clip is excerpted, with permission, from Increasing Healthspan: From Micronutrients to Hormetic Stressors. Thank you to the Institute for Functional Medicine for allowing us to share it.
- ^ Dyerberg J; Madsen P; Møller JM; Aardestrup I; Schmidt EB (2010). Bioavailability of marine n-3 fatty acid formulations. Prostaglandins Leukot Essent Fatty Acids 83, 3.
- ^ 2847723
- ^ Smutna M; Kruzikova K; Marsalek P; Kopriva V; Svobodova Z (2009). Fish oil and cod liver as safe and healthy food supplements. Neuro Endocrinol Lett 30 Suppl 1, .
- ^ Ashley JT; Ward JS; Schafer MW; Stapleton HM; Velinsky DJ (2010). Evaluating daily exposure to polychlorinated biphenyls and polybrominated diphenyl ethers in fish oil supplements. Food Addit Contam Part A Chem Anal Control Expo Risk Assess 27, 8.
- ^ 10.1038/s41598-017-01470-4
Dr. Kalea Wattles: I think our audience will not forgive me if I don’t dive into the supplement piece for a minute. I saw a debate raging in a functional-medicine group yesterday about whether omega-3 supplements are contaminated with things such as PCBs to the same degree as whole fish, and whether we need to be concerned about environmental toxicity in supplements. I would love to hear your perspective.
Dr. Rhonda Patrick: It is good to get a quality supplement. A few things are important. First, I think triglyceride form is important. Lovaza and Vascepa are in ethyl ester form. Ethyl ester is not incorporated into cell membranes as readily. It is not as bioavailable. It absolutely has to be taken with food, preferably with a higher-fat meal.
Some people will take what their doctor prescribes, and compliance is an issue. Triglyceride form is more bioavailable and incorporates into cell membranes much better. I think that’s important.
Second is oxidation status. Fish oil is a polyunsaturated fatty acid, so it is prone to oxidation. There are isolation protocols that can minimize oxidation, such as doing it under liquid nitrogen.
Third-party testing sites test omega-3 oxidation status, PCBs, mercury, and everything else. The best one I use is the International Fish Oil Standards website, or IFOS. It includes many different brands. You can go to the product sheet, click a product, and see batch numbers for different omega-3 supplements. You can then look at the raw data, including oxidation status and the amounts of mercury and PCBs.
I would say the most important things are the concentration of EPA and DHA, triglyceride form, and perhaps oxidation status. Most fish-oil supplements are purified. They are run through a column that removes many of these toxins, so I don’t think contamination is as large an issue.
More importantly, omega-3 fatty acids protect against potential negative effects. As I said regarding the developing fetus, which is much more sensitive to mercury, PCBs, and everything else, omega-3 fatty acids are protective. That is the study I like to cite when I’m asked, “What about the toxins?”
Focus on what we need to get. If you focus only on toxins, you’re not going to get omega-3, or you won’t get enough of it. I think that is much more detrimental than any small amount of mercury or PCBs that might hitchhike in. Omega-3s are very good at lowering inflammation, which is one of the major things you’re worried about with those contaminants.
To me, it is a question of levels. You are getting much more of the beneficial substance, which is going to negate the potential negative effects of PCBs and mercury.
IFOS is a good source. Labdoor is another one. They use a different approach and rank products, so much of the time the top-ranked supplement is sold out. On IFOS, you can find many other supplement brands by region. If you live in Canada, you can find Canadian products. You can also find products in Europe or the U.S.
Go out and find a supplement that makes you feel good. It should have high levels of EPA and DHA, low oxidation, and perhaps lower mercury. Don’t sweat the small stuff.
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Omega-3 News
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- Omega-3 supplementation during pregnancy altered children's brain metabolism a decade later.
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- Fish oil supplement use is linked to a lower risk of severe fatty liver disease.
