Marks Daily Apple
Serving up health and fitness insights (daily, of course) with a side of irreverence.
4 Jun

The Definitive Guide to Fish Oils

I was actually a little surprised that we hadn’t already done a Definitive Guide to fish oil when a Worker Bee suggested it to me. We’ve mentioned it enough, and it’s a hot enough topic that I just assumed we’d done a big comprehensive guide to the stuff. But, as my staff so eagerly likes to inform me, I was completely, utterly wrong (enjoy it now, cause it won’t happen again anytime soon!).

A quick look at the archives revealed that we actually had compiled enough content to make a Definitive Guide – we just had it spread out over several wide-ranging posts from various dates. But that’s not to suggest the following is just a rehash of old content. Rather, I’ve pulled it all up, cobbled it all together, and topped it with some entirely new stuff. The result, I think, should be pretty definitive.

Why Fish Oil?

Okay. Everyone – even peddlers of Conventional Wisdom, low-fat proponents like Dean Ornish, and certain vegetarians – agrees that getting enough fish-based Omega-3 fatty acids in our diets is good for us. In fact, the importance of dietary fish oil just might be the only point where I don’t butt heads with, well, almost everyone else. Still, though recommending a fish oil supplement is generally safe for anyone, it’s important to understand why fish oil is so beneficial. So why should we take it as part of a Primal lifestyle?

It all comes down to Omega-6/3 balance. You can’t talk about fish oil without getting into Omega-3 fatty acids, and discussing Omega-3 fatty acids is useless without understanding their relation to the Omega-6s. We’ve mentioned this relationship multiple times before, but I’ll reiterate: a 1:1 Omega-6::Omega-3 dietary ratio helps keep dangerous inflammation in check. Seeing as how most Omega-6 fatty acids can be found in “vegetable” oils (soybean, corn, peanut, sunflower – to only name a few), fake butter products, grain-fed animal fat, and other modern contrivances, it is understood that Grok rarely encountered them – especially not in the excessive levels most people see today. He was munching on nuts and seeds, sure,  and those have moderate amounts of Omega-6s, but he certainly wasn’t setting up processing plants to press wild maize for the Omega-6 rich oil. Simply put, Grok would have gotten plenty of Omega-3 fatty acids from seafood, wild game, and wild vegetation, with minimal amounts of Omega-6s, enough to give him a 1:1 ratio. On the other hand, the Omega-6 to Omega-3 ratio of the Standard American Diet, replete with fake fats, processed vegetable oils, and grain-fed meat, is said to approach 30:1!

To understand why that imbalance is so harmful, you have to understand eicosanoids. Polyunsaturated fats (which include Omega-3s, like fish oil, and Omega-6s) convert to eicosanoids in the body. Both Omega-6 and Omega-3-derived eicosanoids are important signaling molecules, but each has different effects, both figuring prominently in the body’s response to inflammation. Omega-6 eicosanoids are pro-inflammatory, while Omega-3 eicosanoids are less inflammatory. Omega-3 eicosanoids (the type we get from taking fish oil or eating fatty fish) actually reduce inflammation; in an unbalanced diet heavy in vegetable oils, the Omega-6 eicosanoids far outnumber the Omega-3s and contribute to a lot more inflammation.

As Stephan explains here, there is an intermediary step in the process of conversion from fatty acids to eicosanoids: highly unsaturated fatty acid (HUFA) conversion. Dietary PUFAs are converted into HUFA, which is then stored in cell membranes. When a cell requires eicosanoids, it uses the HUFA stored in the membrane to form them. Here’s the catch, though: the cell doesn’t distinguish between Omega-6 or Omega-3 HUFA for eicosanoid conversion. Whatever’s available in the membrane is what they’ll be using, Omega-3:Omega-6 ratio be damned. And, as Stephan says, “the proportion of omega-6- to omega-3-derived eicosanoids is proportional to dietary intake.”

Ratio matters, big time, and it may take a while before the effects of establishing the O6-O3 dietary balance are visible in your tissue, because you’ve still got to clear out the residual unbalanced HUFA in your cell membranes. But once you do, you’re good to go – just check out the heart health of populations with good HUFA ratios. If data were available, I bet you’d see Grok measure up pretty favorably on that same graph.

So yes, maintaining a balanced Omega-6 to Omega-3 dietary and HUFA ratio is the main reason for supplementing with fish oil, but there are still other benefits. Even if you’ve successfully cut out all vegetable oils and fake butter spreads in favor of grass-fed meat and real fats, there are still a couple reasons – other than for cardiovascular health – for you to supplement with fish oil: the EPA and DHA fatty acids it contains.

Docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) play big roles in the formation of brain and retinal tissue. Huge concentrations of DHA can be found in fetal brain and neural development, especially during the last trimester. Babies, especially those yet to be born, can really benefit from fish oil supplementation. Kinda makes all those calls for pregnant women to avoid fish seem a little misguided, eh? DHA/EPA might also be a boon to the elderly; as we age, cognitive and visual health becomes more important than ever, and low DHA/EPA levels may contribute to the onset of Alzheimer’s disease, other dementias, and vision problems. There’s also been some research suggesting DHA/EPA has some beneficial effect on the risk of various cancers, including prostate, breast, and colorectal. Suicidal depression and schizophrenia, too, may be linked with low levels of essential fatty acids like EPA and DHA. And finally, fish oil supplementation may even help improve insulin sensitivity. Or, you can just check out this comprehensive look at fish oil and chronic disease. Whew! Essential fatty acids, indeed.

If you’re interested in the approximate levels of EPA/DHA in various foods, check out the table in a previous MDA post.

Any Downsides?

Hmmm. Less inflammation, lower heart disease risk, better vision, more neural development, less cancer risk, proven health benefits: what’s stopping us from guzzling gallons of delicious fish oil? Well, the old adage about “too much of a good thing” comes to mind, because there are some caveats.

As stated before, the most important reason to supplement with fish oil is to restore the Omega-3/Omega-6 balance in your diet and promote good heart health. Not all of us have access to grass-fed or wild game, or wild-caught fish, and taking fish oil supplements can be an easy, healthy way to counteract the Omega-6 PUFAs in our lives. But for those of us who eat exactly like Grok and have next to no Omega-6s in our diet, fish oil isn’t as crucial. In fact, taking in more than three grams of fish oil may lead to adverse levels of blood thinning (as it hasn’t actually been observed, don’t worry too much about this one, especially if you’re eating tons of Omega 6, because you need all the fish oil you can get!). And don’t forget that, being a fairly unstable PUFA, fish oil can still be oxidized and contribute to inflammation. In its pure, stable state, fish oil protects the heart and fights inflammation, but oxidized fish oil can still be harmful. To avoid oxidized fish oil, only buy it from reputable sources, test your capsules for rancidity by biting into one, and keep them refrigerated (or at least out of warm areas). Don’t overcook your fatty fish, and don’t cook with fish oil (one study showed a huge drop off in EPA and DHA levels when heated).

A high carb/sugar intake might also make fish oil supplementation a bit risky. As long as you’re keeping dietary sugar and refined carbs low (which, you know, should already be happening), fish oil is a great supplement. But, as Peter of Hyperlipid cautions, diets high in sucrose or alcohol can increase the load on your liver when paired with high dose fish oil supplementation. I know I’m preaching to the choir here, but if you’re taking decent amounts of fish oil every day, watch your sugar and alcohol intake to avoid any liver complications. Though it may not apply to MDA readers, I’m sure you know someone who fits the bill.

Different Sources

Does it matter how you get your fish oil? As long as it’s from a company you trust, and it hasn’t turned rancid (check the expiration dates), you should be fine. Some people like taking bottled fish oil by the spoonful, but some may have trouble with the oily sensation (not to mention the taste of some of those brands!) in their mouths. Cod liver oil is another option; while it’s slightly lower in DHA/EPA levels, it does contain Vitamins D and A. If you’re looking to get more of those vitamins in your diet, cod liver oil might work for you. Most people, however, go for the capsules. They are by far the most convenient (you can easily pop ‘em in your mouth on the go), and those who can’t stand the taste or sensation of actual fish oil can still get the benefits by taking the capsules. Just beware of cheaper brands – while they may be easier on the wallet, they’re also prone to going rancid and causing lethal fish burps.

What It All Means

Unless you’re eating fatty fish every day, following the Primal Blueprint means you’re a prime candidate for fish oil supplementation. See, the typical MDA reader has a low sugar intake, avoids refined carbs, but is often faced with the prospect of eating less than ideal meat and animal fat. We all wish we could dine on wild venison and fresh caught salmon every day, but most of us just can’t. In cases like these (which is the majority of us trying to eat and live right by Grok’s ways), taking 1-3 grams of fish oil each day is a good way to restore the fatty acid balance in our cells, promote good heart health, provide essential fatty acids for our brains, improve protein synthesis after workouts, and counteract some of the downfalls of modern life.

Read my follow-up post to the Definitive Guide to Fish Oils in which I answer some of your most pressing fish oil questions.

Prefer listening to reading? Get an audio recording of this blog post, and subscribe to the Primal Blueprint Podcast on iTunes for instant access to all past, present and future episodes here.

You want comments? We got comments:

Imagine you’re George Clooney. Take a moment to admire your grooming and wit. Okay, now imagine someone walks up to you and asks, “What’s your name?” You say, “I’m George Clooney.” Or maybe you say, “I’m the Clooninator!” You don’t say “I’m George of George Clooney Sells Movies Blog” and you certainly don’t say, “I’m Clooney Weight Loss Plan”. So while spam is technically meat, it ain’t anywhere near Primal. Please nickname yourself something your friends would call you.

  1. Would Grok take supplement?

    Throughout history there have been practitioners of herbal medicine so when Grok felt sick I’m sure he had knew what to eat to make him feel better, or at least knew someone who knew.

    Would Grok take daily supplements? When Grok found a herb that he knew was particularly good, did he eat it all in one go? Nah. Did he take some with him for tomorrow? Did he return daily for more. Sure why not!

    I think however, that moderns attempts to isolate the ultimate compound for health and package it in a easy to swallow package is futile. In the end our bodies need food, whole food with all the good stuff in it in the right balance. Since we live now in a time when our balance is our of whack it is probably smart to supplement the balance with sensible isolated compounds.

    Vit D, Omeaga 3 (maybe K2) seem to be on the top of the list at the moment with our current understanding of the human body, food supply, lifestyle

    grandma wrote on June 6th, 2009
  2. I take 30ml of Melrose Cod Liver Oil daily. To avoid the taste I make up a drinking yoghurt and CLO mix:3 Tablespoons of plain (Greek Style) yoghurt in a mug of water with the 30ml of CLO. No fishy taste and the dairy is fermented. (OK, not strictly Grok but OK according to ‘Nourishing Traditions’; my food bible until Primal Blueprint.

    I also have a second mixture each day: 30ml of Apple Cider Vinegar, 1 teaspoon of raw honey, 1 teasoon of tumeric; with 2 teaspoons of crushed garlic, one teaspoon of crushed chilli and one teaspoon of crushed ginger (with warm water) followed by a raw tomato.

    All up about one-third of daily energy requirements.

    I am finding it difficult to obtain grass-fed meat as all the butchers proudly proclaim that their meat is grain-fed so my Omega 6 levels could be a tad high.

    comley wrote on June 6th, 2009
  3. Snake Oil

    The references to snake oil in this thread reminds me of how nice grilled snake is.

    When in Guangzhou, PR China, check out the Snake Restaurants. One can even select hisorher own snake from the pit in the same way as selecting a fish at a fish restaurant.

    My first time I thought that I was eating eel as I had been told that it was a fish dish ( the shape meant it would be eel -if it had of been fish-)After my third helping I was informed that I was eating snake. Unfortunately snakes are a protected species here in Australia so I can’t try the local supply even if we do sometimes have a snake in our back yard.

    I’m sure that Grok ate many a snake.\

    I understand that the Chinese remove the bile duct and the poison sac before serving but I have read that the bile duct is too valuable to waste on customers.

    comley wrote on June 6th, 2009
  4. Mark

    Most “fish oils” have the DHA and EPA as less than half their oil content. What is the rest of the content? i have asked a number of manufacturers, but all I receive in reply is “spin” about their oils meeting all the required standards.


    Keith wrote on June 7th, 2009
    • A lot of fish oils use borage oil and/or vitamin E to fill out the whole of the capsule. The fish oil I take is 70% Omega-3, which I think is pretty good. I use Nordic Natural Ultimate Omega soft gels.

      hilarydanette wrote on August 24th, 2012
  5. Hey Mark,

    Any thoughts on Krill Oil vs Fish Oil? Read an interesting article on Dr. Michael Eades blog:


    Aaron wrote on June 7th, 2009
  6. Very definitive indeed! I would love to see a follow-up article Mark, or maybe just a couple of follow-up points.

    For example, how much fish oil would you recommend for someone who has just started a primal diet and is therefore extremely unbalanced both hormonally and in terms of excess body fat? Studies I’ve completed with Charles Poliquin through his BioSignature course indicate 1 gram of fish oil per percentage body fat and actually I’ve had great results with this.

    I really liked your point about possible dangers of fish oil when consuming excess alcohol/sugar. I haven’t come across this before – could be a good warning tactic for newbies!

    Kat Eden wrote on June 7th, 2009
  7. I wondered whether those that take omega-3 supplements actually feel any benefits? I wouldn’t want to spend years buying and consuming omega-3 supplements for it to have no effect. Or at least no effect that i could not measure.

    rich wrote on August 15th, 2009
  8. I’m in college and therefore don’t have a lot of money. There’s no way I could consistantly buy the fish oil supplements and keep up with other expenses without my accounts going into the red. Is there a really good fish I could eat regularly that would get the job done to a degree? Anything else I could do?

    Joel M wrote on October 20th, 2009
    • Supplements really are the most cost effective way of getting your Omega 3.

      I think the NOW brand is fairly inexpensive but they will give you fish burps.

      chima_p wrote on October 20th, 2009
  9. I know I’m pretty late but all of you should probably read this:

    Ray could be completely wrong, but he makes a convincing argument. Also, if you think about it, fish was probably a minimal part of Grok’s diet (or zero if he didn’t live near a major body of water). If Grok did eat fish they were probably low fat, coastal warm water fish and shellfish, not the high fat cold water fish like tuna.

    Neal V wrote on January 6th, 2010
  10. Hey Mark, This is a really informative article on the health benefits of fish oils. I wasn’t aware that overcooking fish will degrade the amount of omega 3’s available. Maybe I should start eating more sashimi – of course there is the concern of too much mercury from all that raw fish. I guess I’ll stick with my liquid fish oils. I use Carlson fish oils in lemon flavor, but it’s nice to see you’re now offering your own brand of fish oils.

    re: health benefits of fish oils wrote on February 24th, 2010
  11. I would like to ask mark if he has heard about
    The sacha inchi oil? A fruit from the jungle of
    Peru. A close cousin of the lignan oil. It is reach
    In omega 3.
    Also do you have any research that can prove that
    The consumption of lignan oil may affect the prostate?

    For people that cannot consume fish oil is there any
    Alternative in the vegetable oil world that you
    Can suggest to use?

    Best regards,

    Juan felix

    juan felix wrote on March 9th, 2010
    • I would also like to hear Mark’s thoughts about sacha incha oil.

      Cal wrote on February 22nd, 2011
  12. “Worker Bee”

    What hubris processes an individual to refer to an employee as a “Worker Bee”?

    somk wrote on June 14th, 2010
  13. Hey Mark awesome post. Your readers are all awesome too judging by their comments. Hey, what is your take on the whole fish oil vs krill oil debate? I’ve read some pretty interesting stuff here:

    Jessy wrote on November 11th, 2010
  14. Hi everyone! Im new to MDA and am wondering what brand of fish oil i should take. I am living in Australia so the brands that have been mentioned arent available here. I have found one called Swisse Wild Fish Oil…..”and is one of the only fish oils in the world sourced sustainably from wild fish that swim freely in the pristine waters of the Pacific Ocean free range fish. As a result, Swisse Ultiboost High Strength Wild Fish Oil is free from the high levels of environmental toxins often found in farmed fish….”
    They also have a product called Wild Salmon Oil which has lower EPA and DHA than the fish oil..what are your opinions?

    Alicia wrote on March 4th, 2011
  15. Here is a link to a great fish oil calculator:

    Here is a company that has flavored fish oil without the fish burp and 10% off their listed prices. I have no affiliation…I have just been using and have noticed significant lab value changes as well as the fact that I am just not as banged up any more after my workouts. They have regular sizes as well as travel sizes. Check it out and form your own opinion.

    Derek wrote on March 25th, 2011
  16. I’m taking Fish oil capsules that contain:

    Total 1000 mg fish body oils

    but that only contains:

    320 mg Omega 3 fatty acids (160 EPA & 160 DHA)

    So to get 1-3 grams Omega 3’s thats 3 to 9 capsules ?


    Steve O'Collin wrote on April 21st, 2011
  17. Say I have 3 tins of pilchards (~900g overall) a week. This contains about 9g of Omega-3.
    Do I still need supplements? I guess not.

    These sardines to be precise:

    PS Accidentally hit submit before finishing. Please delete previous post :-)

    James wrote on April 28th, 2011
  18. According to
    (where the author brings up an excellent point – Have you ever wondered why a human would suffer from a fish oil deficiency?)

    Claim: Fish oil helps diabetics and helps prevent diabetes and its complications.

    Truth: Resting blood sugars are consistently higher for fish oil users.(see Endnotes:8,9,10) Insulin amounts had to be consistently increased in diabetics who were using fish oil. Glucose tolerance decreased significantly, and the insulin response was significantly blunted (a bad outcome).

    Claim: Fish oil helps your heart and prevents heart disease.

    Truth: Prostacyclin (PGI2(11—the body’s “natural blood thinner”—is the body’ s most potent natural anti-platelet aggregatory agent. It is also a natural anti-adhesive (anti thrombosis) agent. But prostacyclin levels are reduced by an average of 42% in humans with existing atherosclerosis using fish oil.That means fish oil potentially makes existing heart disease worse, not better. Minimizing platelets from “sticking together” or sticking to an arterial wall should be the #1 concern of a patient with existing cardiovascular disease.

    Elena wrote on May 2nd, 2011
    • hmm… I just started cod liver oil and my sugars have been significantly higher, requiring more injected insulin. I hadn’t made the connection. Thanks for the info.

      Sparrow wrote on August 22nd, 2011
  19. Any thoughts on GNC’s triple strength fish oil product?

    Chris wrote on May 16th, 2011
  20. From what i’ve read, krill oil has higher antioxidant content and since it usually comes in the form of capliques, it doesn’t get rancid easily.

    Toni wrote on June 17th, 2011
  21. HI;
    I realize that this article and its latest related posts are a year old! However, a fellow health enthusiast I just met, let me know about your website.
    I had heard about Omega-3 and PharmaGrade Fish oil and Silent Inflammation about 7 years ago, from Dr. Barry Sears. He is he author of several books, and apparently appears to be the pioneer in this area, with his ground-breaking work on eating very similar to what you have in PB. His earliest book is about 15 years or possibly earlier, I do not recall, as I only stumbled upon it 7 years ago. I changed my life at that point, and was satisfied that eating helped make me much healthier and through eating lifestyle change lost about 45+ of 60 lbs I needed to lose. Then a few months ago,I finally decided to exercise, and started doing research as to what and how and best. In that search came across the concept of Body weight and started introducing it into my routine. About an hour 2-3 times a week, usually 2 – and mixed stretch warm-up, heavy lift, and peak interval of no more than 10 minutes with all-out included. Similar to what i am learning, here, and now modifying.
    BUT, back t main point, it seems your work is built on a lot if not most of what Dr. Barry Sears pioneered? And is just now recently finding its way more and more into fringes of main stream.

    John D. Pilla wrote on June 20th, 2011
  22. Hi Mark,

    You recommend we bite into a capsule, if it is good then what taste should be expect and if it is bad what taste should be expect?
    Thanks for the great articles!!

    Tracy wrote on September 7th, 2011
  23. We all know the importance of omega 3s, but I found an interesting article about supplementing with fish oil on a daily basis. Whole fish may be the best option, but we now need to worry about the mecury in them as Greg said.

    Just curious about your thoughts?

    jonathan wrote on October 29th, 2011
  24. I like the fermented cod liver oil for the natural vitamin D.

    I am in Canada where it is hard to find, but I found a supplier here

    Justin wrote on April 23rd, 2012
  25. Hi,

    I’m a bit of a newcomer to this way of life (5 weeks and counting)but I’m already feeling the benefits!

    I eat smoked mackarel every day for my lunch ( 2 fillets)( but it’s bought from a supermarket). I also still have a few beers / wines on the weekend. Am I getting enough Omega 3 or should I add fish oil supplement?

    Great Website by the way…


    Matty wrote on May 18th, 2012
  26. Hi there, I have tried the Stronger Faster Healthier liquid fish oil and it seems to be good. What is your stance Mark on flavored oils? I am an avid Crossfitter and take 6-9 pills a day before I found the liquid.

    What brand do you suggest or does anyone suggest trying that come in liquid form that have been beneficial to you? I honestly have taken for 4 months strait and dont “notice” an actual physical difference with myself. Or in my training.

    Thanks :)(multi-tasking here)

    Rob wrote on May 23rd, 2012
  27. For this kind of post i will know how the fish product has a oil content. Because its very important before its eating.

    Best natural vitamins wrote on January 2nd, 2013
  28. General question about fish oil supplements … why are the pills so low in fat grams (generally)? Do the producers of fish oil remove some of the natural fat from the oils? Which leads me to my next question – are fish oil pills as effective as liquid cod liver oil? Don’t we ultimately want the unadulterated fish fat grams? Is it detrimental to give the body the Omega 3’s from fish oil without the fat itself?

    Jason Fare wrote on March 23rd, 2013
  29. What about smoked salmon? Where I live, I can net about a hundred salmon a year. Does smoking affect the oil’s properties? We also hot pack can the fish after smoking, which brings it to 330 degrees or so.

    Northdoc wrote on April 1st, 2014
  30. I am a bit sad that all this Daily talked about was fish oil in pills. What about fish oil in fish? The oiliest fish tend to be among the most delicious, if you ask me. Great sources of fish oil? How about salmon or bluefish, cooked with the skin on… YUM! Or fatty tuna sushi – chutoro and otoro. Delicious! Or herring and sardines! And if you automatically think of crackers with sardines, try them in a lettuce leaf or on celery with a dab of yogurt or ricotta. Great stuff
    Of course, NOBODY thinks of getting fish oil this way anymore, or they would not leave the scales on fileted fish. (It’s so much easier to scale a fish while it is whole…) This is a pet peeve of mine. I end up with a huge mess in my sink, trying to scale a piece of fish under running water, so the scales don’t fly… But I LOVE the skin on my salmon!

    Marge wrote on July 31st, 2014
  31. As Stephan explains here – the “here” link links to a post that no longer exists

    Oxdeadface wrote on September 28th, 2014
  32. In all of this, there is one big question that has been left unanswered: if you are going to use an omega-3 supplement, is it better to use a natural form, like wild salmon oil, or carlson’s liquid (both natural triglyceride forms, unprocessed), or should you go for the super concentrated, molecularly distilled or CO2 extracted, highly processed fish oil capsule?

    The natural products are of course lower in omega-3s per serving because they are not artificially concentrated, so…..? Which is it?

    I tend to lean toward wild salmon oil (Solgar’s or Vital Choice’s are good picks), as they have zero chemical residues from heat processing, unlike all concentrated forms of fish oil. There are some who even say that the super concentrated oils are not really even fish oil when you get through with them. They basically are stripped of anything but their EPA and DHA contents, so they are not fish oil.

    Thoughts? This could be an article in itself!

    PJ wrote on October 26th, 2014
  33. Great write up! We’re planning a blog post on how under-rated fish oil is amongst bodybuilders as a supplement. In fact, if we were stranded on a deserted island and had to choose only 3 supplements fish oil would be #3 after protein and a beastly multivitamin.

    Erik wrote on September 16th, 2015
  34. Great information. Don’t forget that Omega 3 from microalgae (the original source of Omega 3) is also a great alternative to fish oil.

    Jane wrote on November 17th, 2015

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