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Fish Oil

Should I Take Fish Oil Supplements? Benefits and Harms

12 minute read

Topics Covered:

  • Why should I take fish oil?
  • Is fish oil hype?
  • Is fish oil even safe?
  • The one thing you need to see on any fish oil supplement label before buying it.
  • Healthy people can make their own “fish oil.”

Quick Summary:

This article will help you understand what supplement companies don’t tell you about their product: processing can turn beneficial omega-3 fatty acids into toxins. You’ll learn why fish oil hasn’t lived up to its hype and get tips for finding the best fish oil supplements.


Why it’s time to talk about fish oil.

In the late 1990s, doctors learned that oily fish contains beneficial fatty acids not easily found in the food supply and started recommending oily fish and fish oil supplements to their patients. Twenty years later, fish oil became America’s most popular dietary supplement. Eight percent of all US adults are now taking fish oil, which is pretty astounding when you consider that nobody had heard of fish oil 25 years ago and pretty much zero percent of people were taking it. 

Other supplements that are the same idea as fish oil, meaning they’re supposed to have the same benefits and can have the same drawbacks, are krill oil, DHA/EPA, algae oil, and good old-fashioned cod liver oil.


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Why would anyone want to take fish oil?

The reason people take fish oil is for the special set of omega-3 fatty acids: DHA and EPA. These letters stand for the chemical names for two specific kinds of omega-3 fatty acids that our bodies need to help control inflammatory reactions, prevent blood clotting, and build healthy cells, especially in our nervous system. 

Marketing claims around fish oil include:

  • Anti-inflammatory benefits
  • Brain building effects
  • Help for dry eyes
  • Helps to prevent AMD (the most common cause of blindness)
  • Helps people with fatty liver
  • Helps reduce pain in rheumatoid arthritis
  • Reduces triglycerides
  • Prevents heart attacks
  • Prevents strokes
  • Prevents the onset of mental disorders in those at risk
  • Prevents Alzheimer’s

That’s a lot of wonderful things! But is it possible that one little capsule could really do all this?

Fish oil: Hype or Scam

A decent question, one that I’ve seen a lot of people asking on google because more and more we’re learning the supplement industry is rife with profiteering bandits—just like the pharmaceutical industry. So let’s take a look at the complete answer to the hype or scam question.

The bottom line is it’s not just hype.

Fish oil’s supposed benefits are not completely fraudulent claims because there is some basis in reality. 

It is totally true that omega-3 fats represent a family of nutrients our body requires but cannot make on its own so we need to eat, drink, or otherwise consume these nutrients in order to be healthy. If we don’t, we’ll be deficient in nutrients and by definition malnourished. When we’re nutrient-deprived and malnourished, all kinds of things can go wrong with our health.

Conversely, if we are malnourished and have developed any of the many medical problems that develop due to lack of the omega-3 family of fatty acids and suddenly start getting plenty, then that one change can reverse many medical problems. This is why the many health claims made by the fish oil supplement companies are not complete fiction. 

Unfortunately, the reality of fish oil supplementation does not come close to the potential.

The reason you should NOT take MOST fish oil supplements.

The sad truth is that most fish oil supplements are actually bad for you.

Multiple studies show that fish oil supplements are loaded with toxins. You may think I’m talking about environmental toxins, like PCBs or mercury, and other pollutants. Those are in fish, too, but that’s not what I’m talking about. The kinds of toxins I’m talking about are actually more harmful than heavy metals and PCBs.

We have to consider that fish oil is a processed food product. We’re not necessarily getting that special omega-3 family of fatty acids that we think we’re getting when we’re taking fish oil instead of eating oily fish. It has to do with the impact of processing on the omega-3 family of fats.

Numerous toxins develop during fish oil processing.

These toxins are not environmental pollutants and don’t exist in fish. After processing, they are present in fish oil in much greater quantity than any environmental pollutants, which makes these toxins a more serious threat to your health. 

If fish oil supplements contained fish oil in the form that nature made it, fish oil supplements truly could work well to alleviate numerous ailments. The reason most fish oil supplements not only fail to show benefits when studied and may do you more harm than good is that very few fish oil supplements contain fish oil in the form that nature made it.

What do I mean by that?

Fish oil undergoes a chemical change during processing. The omega-3 fatty acids in oily fish are very fragile and the process of extracting oil from fish damages the oil. The chemical fragility of omega-3 fatty acids presents a manufacturing challenge that is not easily surmounted and only a few companies currently appear to make the effort to mitigate those technical challenges. The rest are selling fish oil supplements that are actually more likely to be harmful to your health than beneficial.

The image below is from a study that looked at three over-the-counter brands and one prescription brand of fish oil. They measured how many toxins were present in each and presented their results in this graph.

study finds toxic compounds in most popular fish oils
If you’re buying a popular brand of fish oil, you may be getting a belly of toxins. Watch the youtube video below for a more detailed discussion of this image. Image with permission from source: https://www.sciencedirect.com/science/article/pii/S0006291X16321878#fig3

It shows that three of the four supplements tested far exceed the threshold of acceptable levels of toxin present on a percentage basis in the oil. All three over-the-counter brands exceed the level dramatically.

It also shows that the prescription omega-3, the stuff a doctor has to prescribe and costs about $200 per month (and insurance may pay for it), actually did not have so much toxin that it exceeded the threshold. But it still had some so that just shows you that these omega-3 fatty acids are very very fragile and they break down very easily and even under the best possible controlled environment of a prescription quality lab you still get some toxins.

Why does processing damage fish oil?

The chemical challenge fish oil manufacturers face is called oxidation. Oxidation is the reason fish oil supplementation has not lived up the expectations. Oxidation transforms the beneficial omega-3 into toxins. This poses two problems to you, the consumer.

First, oxidation destroys the beneficial omega-3 fatty acids. Not all of them, but a lot of them. This loss of omega-3 occurs during the normal heating and refining steps that most manufacturers employ to make their fish oil.

Second, oxidation creates toxins. Oxidation chemically changes the beneficial compounds, creating new ones that don’t exist in fish and in some cases wouldn’t exist without the heating and refining steps of processing. Oxidizing fish oil creates many hundreds of new compounds that simply don’t exist to any measurable level in the fish itself, some of which are extremely toxic.

Unless you know what to look for, any fish oil supplement you buy is very likely to contain unacceptably high levels of toxic breakdown products of fish oil with known cell killing, telomere shortening, mitochondrial and microbiome damaging, as well as DNA-mutating properties. This makes most fish oil supplements worse than a waste of money. They really should not be available to consumers because they’re loaded with toxins.

The one thing you need to see on any fish oil supplement label before buying it.

Any fish oil supplement company that’s not a complete fraud will be able to speak to this problem of oil oxidation. What you want to look for in the marketing is that the company specifically mentions controlling for oxidation. The actual language may say “non-oxidized” like the supplement in the image below.

The actual technology that they use is called “supercritical extraction with carbon dioxide.” That’s a mouthful, and it’s not just hype actually that’s a real thing. They use carbon dioxide that they pump in to the processing environment to replace the oxygen normally present in the air. That’s one way you can control oxygenation reactions; you just remove the oxygen.

Make sure to buy fish oils that say this on the label
Make sure to buy fish oils that detail how they control oxidation. Supercritical extraction is not a really unkind form of extraction, but rather a new technology that displaces the oxygen-rich air with CO2 that won’t damage the fish oil.

Keep in mind, that this language is a good sign but it’s not a guarantee. It doesn’t necessarily mean that they actually do control for oxidation and that is because this is an essentially unregulated industry. But it does mean that I wouldn’t touch a fish oil that doesn’t say that it’s “non-oxidized” and ideally they would also say how they ensure it’s not oxidized, as this one does: Supercritical extraction with CO2.

If Your Metabolism is Healthy Your Body Can Make “Fish Oil.”

Not all omega-3 is created equal.  There’s a common form of omega-3 and a very special form of omega-3. Omega 3 is a kind of fatty acid and it comes in different lengths. Lots of plant and animal foods contain shorter omega-3, but the omega-3 in fish oil is unusually long. Our bodies need both the shorter, 18 carbon form and the unusually long, 20 carbon-plus forms.

If your metabolism is healthy, you can elongate any 18 carbon omega-3 fatty acid into a 20 plus carbon omega-3 fatty acid, thus in a sense manufacturing your own fish oil. If your metabolism is not healthy, the enzymes that elongate omega-3 are not functional.

There’s actually a blood test that you can easily get that will give you a good idea as to whether your body can elongate omega 3 fatty acids. I talk about that in the video below as well as the simple blood test you’ve probably already had that will tell you if your metabolism is healthy enough to make its own “fish oil” from ordinary foods containing omega-3.


Why Trust Me?

Here are a few reasons:

  1. I’m an MD and the advice given here on DrCate.com is the same I give my patients. If something works, I share it here. If something doesn’t work, I share that here too.
  2. I studied biochemistry at Cornell U before medical school. That matters becuase the biochemical value of our foods will be altered by processing, and most folks live off processed oils whether they know it or not.
  3. I don’t sell any supplements so I have no conflicts of interest. This website is purely educational and so if the information I give out is incorrect, this website does nothing for anyone.

References and Resources

NIH article on Omega-3 Supplementation

https://www.nccih.nih.gov/health/omega3-supplements-in-depth

Articles about Toxins in Fish Oil

https://www.sciencedirect.com/science/article/pii/S0006291X16321878#fig3

https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0244688


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List of Good Fats and Oils versus Bad

Dr. Cate

With over two decades of clinical experience and expertise in genetic and biochemical research, Dr. Cate can help you to reverse metabolic disease and reshape your body.

This Post Has 19 Comments

  1. Do you consider all PUFA’s bad? Because isn’t omega 3 and DHA in fish and fish oil all technically polyunsaturated fat and even olive oil has some PUFA in it. So is it all pufas that are bad or just the seed oils? And why is that because I thought what made the seed oils bad is that they were PUFA’s.

  2. Dr Cate — Thank you for posting the Fish Oil information! I now makes me wonder if the fish oil I use daily is safe.

    Do you have any thoughts about Nordic Naturals Ultimate Omega 2X (2150 mg total omega-3s)? Is this a good product to use? I’ve been taking it for a few years. They are claiming to use an “patented oxygen-free manufacturing process”. Below is from their website:

    https://www.nordicnaturals.com/consumers/ultimate-omega-2x

    EPA: 1125 mg; DHA: 875 mg; Other Omega-3s: 150 mg

    Ingredients purified deep sea fish oil (from anchovies and sardines), soft gel capsule (gelatin, glycerin, water, natural lemon flavor), natural lemon flavor, d-alpha tocopherol (antioxidant), rosemary extract (a natural preservative).

    No gluten, milk derivatives, or artificial colors or flavors.

    All Nordic Naturals’ fish oil products are offered in the triglyceride molecular form—the form naturally found in fish, and the form your body most easily absorbs.* Everything we make is non-GMO and third-party tested, surpassing the strictest international standards for purity and freshness. Certificates of Analysis are available for any product. Nordic Naturals fish oils are Friend of the Sea (FOS) certified and sustainably made in a zero waste facility powered by biofuel.

    MANUFACTURING STANDARDS

    Most of the concentrated fish oils on the market today are formulated for cost-savings rather than quality and efficacy. Their manufacturing process is cut short, resulting in omega-3s as ethyl ester molecules—synthetic fats with only about 30 years of history in the human diet.

    Not at Nordic Naturals. All of our omega-3 fish oil products are produced in the triglyceride form, which is the form naturally found in fish and the form the body most easily recognizes and absorbs.* Triglyceride-form fish oils require more manufacturing steps, and take longer to produce, but for us, there’s no other way. Our patented oxygen-free manufacturing process allows us to deliver industry-leading purity and freshness levels documented by third-party test results.

    They offer a full CERTIFICATE OF ANALYSIS on-line where you Enter the Lot Number on your bottle to pull it up.

    Any insight would be appreciated.

  3. Dr. Shanahan: Thank you for writing The Fatburn Fix and revealing what the food and medical industries are doing to our “food” and our bodies. We are being poisoned by greed for profit.
    I do have one technical correction you might make when the book is next revised. I worked as an operations engineer at a nuclear power plant for 15 years and immediately saw this problem.
    On page 81 you state “When you get your household electric bill, the total amount of energy you’ve used is measured in units called watts.” And “Calories and watts are just different units if energy, and they’re actually interchangeable”.
    Watt is a unit of power, not energy. Energy is power multiplied by time (watt-seconds or kilowatt-hours). A joule is a watt-second of electricity. Your electric bill usage could be listed as 3,600,000 joules or 1000 kilowatt- hours.
    Kilocalorie (calorie) is a unit of energy. We can convert both kilocalorie and watt-minutes into BTUs (British Thermal Units). One BTU is the energy to raise one pound-mass of water one degree Fahrenheit.
    1 kilocalorie = 3.966 BTUs
    1 Kwh = 3413 BTUs

    3.966 BTU/kcal x Kwh/3413 BTU x 1000 watt-hr/Kwh x 60 watt-min/watt-hr =
    69.72 watt-minutes/kcal

    Or simply Google “kilocalorie to watt minutes” and get 69.78.

    Or about 70 watt-minutes / kcal.

    “Sitting here reading, you’re burning about 1 calorie per minute (70 watt-minutes), which over the course of an hour equates to 60 calories (70 watt-hours).”

    Thanks again for the information (truth) in The Fatburn Fix.

  4. I read The Fatburn Fix with great interest. And you are right. Vegetable oil is in everything! I now read every label and even ask restaurants what oil they fry with. Both my wife and I ate poorly for years. Her legs were heavy when we first met. Over 30 years her weight doubled; most of it in her upper arms, butt, hips, thighs, and calves. We have both been to a nutritionalist who stressed no gluten, sugar, dairy, caffeine, and alcohol; but vegetable oils were not mentioned. My wife lost 100 pounds; but very little reduction in the afore-mentioned areas. She has since gained a lot of the weight back. My wife just took an on line questionaire about lipedema. She scored 100% for lipedema. Does eating (and storing as fat) vegeatable oils exacerbate weight loss problems for those with lipedema?

  5. I took fish oil caps for years. I stopped because I no longer wanted to take fish out of the ocean just so they could be ground up to produce fish oil. There are creatures in the sea that need sardines and other oily fish more than I need fish oil caps. I switched to plant based, flax seed oil caps.

  6. I’ve been taking Garden of Life’s Omega-3 supplement semi-daily for awhile. Their site says, “…made from the purest fish oil utilizing dual supercritical CO2 extraction technology that delivers 850mg of omega-3s in just one softgel. Unlike fish oils, which are two-thirds saturated fat, it contains no saturated fat.”

    This seems to pass muster based on your criteria. Thoughts?

  7. How about Dropi? They claim they only do cold processing. Is this good enough?

    “It means that during the whole process, we never heat the product over 42°C (107,6°F).”

  8. Ha. Interesting ploy. “In their naturally formed and balanced triglyceride state” only means they don’t process it to intentionally remove the fatty acids from the glycerol backbone, and I don’t think there’s a supplement on the market that carries out that process. So in other words they’re blinding us with science. Or trying to. I would skip.

  9. By the way, I scanned your latest book to not find mention of fish oil supplements (perhaps I missed it). Is the info in this blog just your updated research and you do, in fact, recommend it daily?

  10. Hi Dr. Cate,

    I purchase Costco/Kirkland brand “Sustainably Sourced Wild Alaskan Fish Oil”. The label doesn’t make any mention of oxidation, however it says “Kirkland Signature 1400 mg Wild Alaskan Fish Oil offers a whole-food alternative to highly processed fish oils. Our edible oil is made in a food grade facility, using a state-of-the-art cold-pressed extraction process, which retains Omega-3s in their naturally formed and balanced triglyceride state…” Can you help identify whether the “whole-food alternative” Costco/Kirkland brand passes the non-oxidized test?

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