Published on March 6, 2022

As many as 50% or more of the omega-3 fish oil supplements on the market are oxidized; why choosing high quality fish oil supplements is essential and how to find them

Key Points

  • EPA and DHA from fish oils can provide many amazing health benefits but are also very vulnerable to oxidation, which can have negative effects on health.
  • The study reviewed demonstrates the differing effects of oxidized fish oil supplements compared to high quality fish oil supplements on blood lipid values, and the importance of consuming high quality supplements with a lower oxidation value
  • Look for third party validation on fish oil supplements for quality testing and practices, and take measures to help prevent oxidation after purchasing your fish oil supplements

EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid) are two very important omega-3 fatty acids found in fatty fish and other marine sources, which are essential to our health. Higher omega-3s have been associated with improved cognitive function and cardiovascular health, lower risk of dementia, lower risk of cancer, longer life, and a reduced relative risk for death from any cause, including COVID-19. They are beneficial for normal vision, anti-aging, skin health, maternal health, immune system, brain health, heart health, normal liver function, joints and muscles, and more.

EPA and DHA in Fish Oil Supplements Are Prone to Oxidation

Unfortunately, the EPA and DHA that provide many amazing health benefits are also very vulnerable to oxidation. Oxidized fish oil supplements have been shown to have negative effects on health.

A way to measure the amount of oxidation in fish oil supplements is through using two measurements: the peroxide value (PV) and the anisidine value (AV). According to the Global Organization for EPA and DHA (GOED), the maximum limit for oxidation in fish oil supplements is reached with a PV of 5 mEq/kg or higher and/or an AV of 20 or higher. As many as 50% or more of the omega-3 fish oil supplements on the market exceed one or both of these limits.

What are the Health Consequences of Oxidized Fish Oil Supplements?

A study by Rundblad et al. looked at the effects of oxidized fish oil supplements and high-quality fish oil supplements on specific cholesterol particle measurements using a randomized, double-blind controlled trial. The study enrolled 54 adults between the ages of 18 and 50 years; 17 received high-quality fish oil supplements, 18 received oxidized fish oil supplements, and 19 received high-oleic sunflower oil capsules. Both the high-quality and oxidized fish oil supplements had the same amount of omega-3 fatty acids (1.6g EPA + DHA per day), however, the oxidized fish oil supplements had a PV of 18 mEq/kg and an AV of 9, with a total oxidation value (2PV + AV) of 45. Both the high quality fish oil supplement and the sunflower oil capsules had a total oxidation value of 11. The supplements were given for 7 weeks.

Blood samples were taken at baseline, 3 weeks, and at the end of the 7 weeks, with measurements including routine lipids, lipoprotein subclass profiling with lipid concentrations within fourteen subclasses, fatty acid composition, abundant proteins, and various low-molecular-weight metabolites.

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Overall, the study found that supplementing with the oxidized fish oil increased the following, while supplementing with the high quality fish oil resulted in significantly reduced concentrations of

  • intermediate-density lipoprotein (IDL) particles
  • large, medium and small LDL particles
  • total lipids, phospholipids, total cholesterol, cholesteryl esters and free cholesterol in IDL and LDL subclasses

This study demonstrates the differing effects of oxidized fish oil supplements compared to high quality fish oil supplements, and the importance of consuming high quality supplements with a lower oxidation value.

How Do You Choose a High Quality Fish Oil Supplement?

There are several third-party organizations that offer quality stamps of approval for fish oil supplements, including GOED and IFOS (International Fish Oil Standards), both of which have a list of brands that adhere to their set standards of quality, safety, purity, and good manufacturing practices. All quality products should also have a current good manufacturing processes certification (cGMP) to ensure the proper use of design, monitory, and control of processes and facilities.

Tips to help prevent oxidation in your fish oil supplements include

  • Storing supplements in opaque bottles or choosing dark-colored softgels
  • Storing supplements in a cool place, out of direct sunlight (but not in the freezer!)
  • Limiting air exposure by keeping the product bottle sealed when not in use (blister-packs are a great option)
  • Toss products that have an extreme, fish-smell odor or are past their expiration date; fish-flavored burps may also be a sign of a rancid supplement

Measure the Omega-3 Index and AA:EPA Ratio to Ensure Proper Omega Intakes

GrassrootsHealth offers several testing options to help measure the status of omega-3 and omega-6 fatty acids – the Omega-3 Index, AA:EPA Ratio, and Omega-6:Omega-3 Ratio. Learn more about these tests and the differences between them here. More information on how to improve these test results can be found here.  These and more can be measured with your vitamin D level as part of participation in the D*action project.

Having and maintaining healthy vitamin D levels and other nutrient levels can help improve your health now and for your future. Choose which additional nutrients to measure, such as your omega-3s and essential minerals including magnesium and zinc, by creating your custom home test kit today. Take steps to improve the status of each of these measurements to benefit your overall health. With measurement you can then determine how much is needed and steps to achieve your goals.  You can also track your own intakes, symptoms and results to see what works best for YOU.

Enroll in D*action and Test Your Levels Today!

What Does it Take YOU to Get Your D to 40 ng/ml (100 nmol/L)?

Did you know your health could be greatly affected by making sure you have a vitamin D level of at least 40 ng/ml (100 nmol/L)? Help us help you.

STEP 1 - Do you know what your vitamin D level is? If not, be sure to test today to find out.

STEP 2 – Determine your target level. Are you at your target level? Experts recommend a level of at least 40-60 ng/ml (100-150 nmol/L).

STEP 3 – Need to boost your level? Use the D*calculator to see how much vitamin D it may take to reach your target. Opt for the Loading Dose for a quicker boost.

STEP 4 – Optimize how your body absorbs and utilizes vitamin D with co-nutrients and these simple steps.

STEP 5 – Re-Test! This is an important step to make sure you have reached your target level, and to ensure you are not taking too much! Re-testing after 3-4 months is recommended.

STEP 6 – Adjust, Repeat…

Give your immune system the nutrients it needs to support a healthy you and protect yourself from unnecessary diseases, especially COVID-19.


The first Randomized Controlled Trial on vitamin D and COVID-19 has shown a 96% lower risk of ICU admission for those receiving vitamin D (as 25(OH)D to quickly boost vitamin D blood levels) along with the standard treatment, compared to those receiving standard treatment alone.

These results support many previous observational studies showing a relationship between vitamin D levels and intake and COVID-19 severity.

Review the Latest Nutrient Research for COVID-19

GrassrootsHealth Nutrient Research Institute has launched the new Immune Boost project with the use of our myData-myAnswers nutrient health system that nearly 15,000 people are already using for their health. Specific markers that influence immune health are suggested for testing as part of this project including:

  • Vitamin D
  • Omega-3 Index
  • Essential elements magnesium, selenium, and zinc
  • hsCRP

Our goal is to demonstrate how one can use the Nutrient Research Model established by Dr. Robert Heaney to show the effect of vitamin D serum levels of at least 40 ng/ml (100 nmol/L) on risk reduction for all ethnicities in the population. Status and intake of other nutrients will also be analyzed for any type of relationship to immune status and symptom severity. Join the project today!

Please let us know if you're interested in helping sponsor this project.

CLICK HERE for updates and new information about the project.

Through GrassrootsHealth Nutrient Research Institute, you can also test your essential elements magnesium, copper, zinc and selenium, toxins such as lead, mercury and cadmium, as well as your omega-3 levels, inflammation levels and thyroid stimulating hormone (TSH) level. Find out your levels today! Log on to the test selection page (click the link below) to get your tests and see for yourself if your levels can be improved.

Make sure you track your results before and after, about every 6 months!

Click Here to Access the Test Page

How can I track my nutrient intake and levels over time?

To help you track your supplement use and nutrient levels, GrassrootsHealth has created the Personal Health Nutrient Decision System called

For each specific supplement, you can track what days you take it, how much, and many other details.  This will help you know your true supplemental intake and what patterns of use work for you to reach and maintain optimum nutrient levels. Check it out today!