Fish oil: The natural triglyceride form is better

If you have a choice, the triglyceride form of fish oil is preferable. The triglyceride form, i.e., 3 omega-3 fatty acids on a glycerol "backbone," is the form found in the body of fish that protects them from cold temperatures (i.e., they remain liquid at low ambient temperatures).

Most fish oils on the market are the ethyl ester form. This means that the omega-3 fatty acids have been removed from the glycerol backbone; the fatty acids are then reacted with ethanol to form the ethyl ester.

If the form is not specified on your fish oil bottle, it is likely ethyl ester, since the triglyceride form is more costly to process and most manufacturers therefore boast about it. Also, prescription Lovaza--nearly 20 times more costly than the most expensive fish oil triglyceride liquid on a milligram for milligram basis--is the ethyl ester form. That's not even factoring in reduced absorption of ethyl esters compared to triglyceride forms. Remember: FDA approval is not necessarily a stamp of superiority. It just means somebody had the money and ambition to pursue FDA approval. Period.

Taking any kind of fish oil, provided it is not overly oxidized (and thereby yields a smelly fish odor), is better than taking none at all. All fish oil will reduce triglycerides, accelerate clearance of postprandial (after-eating) lipoprotein byproducts of a meal (via activation of lipoprotein lipase), enhance endothelial responsiveness, reduce small LDL particles, and provide a physical stabilizing effect on atherosclerotic plaque.

But if you desire enhanced absorption and potentially lower dose to achieve equivalent RBC omega-3 levels, then triglyceride forms are better.

Here are cut-and-pasted abstracts of two of the studies comparing forms of fish oil.

Bioavailability of marine n-3 fatty acid formulations.

Dyerberg J, Madsen P, Moller JM et al. 
Department of Human Nutrition, Faculty of Life Sciences, University of Copenhagen, Copenhagen, Denmark.


The use of marine n-3 polyunsaturated fatty acids (n-3 PUFA) as supplements has prompted the development of concentrated formulations to overcome compliance problems. The present study compares three concentrated preparations - ethyl esters, free fatty acids and re-esterified triglycerides - with placebo oil in a double-blinded design, and with fish body oil and cod liver oil in single-blinded arms. Seventy-two volunteers were given approximately 3.3g of eicosapentaenoic acid (EPA) plus docosahexaenoic acid (DHA) daily for 2 weeks. Increases in absolute amounts of EPA and DHA in fasting serum triglycerides, cholesterol esters and phospholipids were examined. Bioavailability of EPA+DHA from re-esterified triglycerides was superior (124%) compared with natural fish oil, whereas the bioavailability from ethyl esters was inferior (73%). Free fatty acid bioavailability (91%) did not differ significantly from natural triglycerides. The stereochemistry of fatty acid in acylglycerols did not influence the bioavailability of EPA and DHA.
(Full text of the Dyerberg et al study made available at the Nordic Naturals website here.)

Eur J Clin Nutr 2010 Nov 10. 

Enhanced increase of omega-3 index in response to long-term n-3 fatty acid supplementation from triacylglycerides versus ethyl esters.

Neubronner J, Schuchardt JP, Kressel G et al. 
Institute of Food Science and Human Nutrition, Leibniz Universität Hannover, Am Kleinen Felde 30, Hannover, Germany.


There is a debate currently about whether different chemical forms of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) are absorbed in an identical way. The objective of this study was to investigate the response of the omega-3 index, the percentage of EPA+DHA in red blood cell membranes, to supplementation with two different omega-3 fatty acid (n-3 FA) formulations in humans. The study was conducted as a double-blinded placebo-controlled trial. A total of 150 volunteers was randomly assigned to one of the three groups: (1) fish oil concentrate with EPA+DHA (1.01?g+0.67?g) given as reesterified triacylglycerides (rTAG group); (2) corn oil (placebo group) or (3) fish oil concentrate with EPA+DHA (1.01?g+0.67?g) given as ethyl ester (EE group). Volunteers consumed four gelatine-coated soft capsules daily over a period of six months. The omega-3 index was determined at baseline (t(0)) after three months (t(3)) and at the end of the intervention period (t(6)). The omega-3 index increased significantly in both groups treated with n-3 FAs from baseline to t(3) and t(6) (P < 0.001). The omega-3 index increased to a greater extent in the rTAG group than in the EE group (t(3): 186 versus 161% (P < 0.001); t(6): 197 versus 171% (P < 0.01)). Conclusion: A six-month supplementation of identical doses of EPA+DHA led to a faster and higher increase in the omega-3 index when consumed as triacylglycerides than when consumed as ethyl esters.

Comments (43) -

  • Flavia

    2/2/2011 2:05:51 PM |

    Thank you for the heads up! Once I exhaust my fish oil, I will switch to the triglyceride form.

    I wanted to drop by and thank you for scaring the sh*t out of me regarding a high wheat carby diet and atenolol.

    My blood pressure seems to be genetic and quite stubborn, but since taking your advice (plus some supplements) I have been able to lower it from 150/100 to around 128/92 and going down.

    Something I have also pulse used to be quite high all the time- Around 80-90 (I am 29). Now it is always in the 60s. Could this be due to the supplements? Or low carb? Is this healthy?

  • Anonymous

    2/2/2011 2:27:44 PM |

    Which brands do you recommend?
    I can't find where my cotsco fish oil states which type it is?

  • TedHutchinson

    2/2/2011 2:28:02 PM |

    In case anyone else uses Nature's Answer, I've just contacted their customer services who say
    " This product IS the triglyceride form.
    Thank you,
    Ellen Kamhi PhD RN"
    At $14.95 from Iherb 16 fl oz it's good price and tastes fine.
    CODE WAB666 saves $5 off initial IHERB purchase. Maybe cheaper elsewhere but IHerb ship cheap to UK.

  • Dr. William Davis

    2/2/2011 3:21:47 PM |

    Hi, Flavia--

    Those are all positive changes, including the drop in heart rate. It reflects a reduction in adrenaline. A reduction in heart rate is a powerful marker for overall health.


    Costco is the ethyl ester. It is a fine brand, just less well absorbed, of course.

  • Anonymous

    2/2/2011 4:03:36 PM |

    I have some vitamin D gelcaps and they smell like fish. Are these oxidized too?

  • Michael

    2/2/2011 4:19:33 PM |

    You say not "overly oxidized" at one point in the post.  

    I am generally concerned about the fish oil I buy being oxidized.  There is a brand of fermented fish oil which purports to avoid this problem of oxidation with storage.  

    Is it your position that concerns about oxidation are sometimes (or at least mine) are overblown?  Or that the oxidation that occurs with normal storage etc. is acceptable?

  • Jack

    2/2/2011 4:26:08 PM |

    Hi Dr Davis,

    If I eat high omega-3 wild salmon once a week, high omega-3 wild sardines once a week, grass pasture butter with 225mg of naturally occurring omega-3 per serving, and organic eggs that have a bit in there as well, do you think I am getting enough for a healthy ratio? I also take the Green Pastures FLCO and HVBO blend.

    I do not eat ANY vegetable oils, ever. I only use coconut oil and ghee to cook, so my O6 intake has got to be pretty low.

    What are your thoughts on being able to obtain adequate levels of healthy omega-3 from foods where it is naturally occurring?

    Jack Kronk

  • Anonymous

    2/2/2011 4:29:17 PM |

    Dr. Davis (or others): Based on what you say, since my fish oil brand is silent on what kind, I'm assuming it's the ethyl ester form.  But, I just wanted to check to see if anyone knows for sure: the brand I've been using is Carlson ("The Very Finest Fish Oil"), liquid form in a bottle - not the capsules.

  • Anonymous

    2/2/2011 5:01:52 PM |

    I take the Carlson lemon cod liver oil. Is their any disadvantage to this over fish oil?

  • Anonymous

    2/2/2011 5:13:20 PM |

    What about Krill oil?

  • Flavia

    2/2/2011 6:00:08 PM |

    Dr. Davis said: "Those are all positive changes, including the drop in heart rate. It reflects a reduction in adrenaline."

    No wonder every time I take my BP at Walmart my pulse is higher!!

  • Anonymous

    2/2/2011 7:01:13 PM |

    Where does krill oil fit into this?

  • Might-o'chondri-AL

    2/2/2011 7:18:24 PM |

    Natural Factors omega-3 is ethyl ester processed form.

  • Lucy

    2/2/2011 7:21:44 PM |

    Dr. Davis,

    Can you comment on the recommended dose for an ApoE 3/4 like me?  I've been told by a BHL educator not take any, but I don't like the idea of that.  I was thinking I may try just 500-600mg/day.  Of course, I've been using Kirkland's which apparently is less bioavailable anyway...

  • Vin Kutty

    2/2/2011 10:53:27 PM |

    As a nutritionist who's worked in the fish oil industry for 20+ years, I may be able to add some insight.

    Yes, Triglyceride (TG) and Re-esterified triglyceride (rTG) forms are better absorbed than the Ethyl Ester form (EE). At least in the short term. And the Phospholipid (PL) form is roughly 50% better absorbed than rTG.

    Then why don't we all take PL form found in Krill oil? Well, there isnt much Omega-3 in Krill to begin with. And the PL-bound Krill Omega-3 are very temperature sensitive, so you won't see anyone concentrating it.

    BTW, the folks at Neptune Krill Oil have some unpublished data that shows the difference between TG and EE diminishes to insignificance over time.

    TG form is natural, no need for pre-conversion before absorption. That does not mean that your body won't use EE. It will. Just requires another step. It's just that TRUE natural TG is not very concentrated. Usually about 30% Omega-3 or so. Anything above 50% is likely to be EE. But most EU nations only allow TG form, so if you want a concentrated fish oil, you jack it up to 60 or 70% as EE and then re-esterify it. Additional process and can be done, but it will cost you. I'm currently working with some 90% rTG material. This raw material is 10 to 20X more expensive than what goes into Walmart brand fish oil.

    I'm guessing (but it's a good guess) but more than 95% of fish oil studies are done on EE form. So all the benefits you've read about don't go out the window if you are taking EE instead of TG. Forget Lovaza, next-gen EPA-based drugs like Epadel, Epanova and still-pending AMR-101 are all EE.

    Most fish oils, if not all, sold at retail stores are EE. Because it is cheaper. Specialty and online sources are your best bet for TG and rTG.  Go to 3rd party testing IFOS website and look under product type - it will tell you if it is EE or TG.

    Issues with the Dyerberg study: 1) 2 weeks is way too short a duration to figure this out. 2) they did not compare TG oil to a placebo (corn oil?). Instead, they compared it to EE. Comparison to placebo would have put things in perspective. The Neubronner paper addresses this issue.

  • Anonymous

    2/2/2011 11:19:46 PM |

    As I understand it, part of the tradeoff involves potency and how much EPA/DHA you can pack into a capsule. Ethyl esters are going to be more "compact" than trigylceride chains. I take Life Extension brand, and I honestly don't know which form it is. Perhaps it is the ester form. I get 3600 mg of combined Omega 3 activity from six capsules a day. If the trigyleride form would mean 10 or 12, I don't know that the trade is worth it in money or hassle. I know some of these other brands like Pharmax are supposed to be good, but I draw the line at doing "shots" of unencapsulated fish oil!

    As an aside, does anyone have any suggestions for me? I'm 40, pretty close to ideal weight, non diabetic and I still struggle with high TG, now 292 even with fish oil and 1 gram a day of IR niacin... Not a big wheat eater either although I do have a nasty breakfast cereal habit.

  • Ned Kock

    2/2/2011 11:40:30 PM |

    It is worth noting that as little as 38 g of sardines provide more "net" O3, of the "good" type, than 2 fish oil softgels:

  • Anonymous

    2/3/2011 1:00:28 AM |

    Dr Davis

    do you know which is the best KOsher fish oil?
    most of brands have vegetarian capsules, but there is a liquid one from Nutri-supreme research

  • Davide Palmer

    2/3/2011 3:21:31 AM |

    Thank you, thank you. At least there are some honest doctors (as Dr. Davis) who are not robots and don't view the FDA's stamp of approval as divinely authoritative and perfect.

  • Rick

    2/3/2011 3:53:04 AM |

    Just to check: Are triglyceride forms always in bottles? Or can we also get them in capsules?

  • Anonymous

    2/3/2011 5:02:07 AM |

    While exploring this subject I came upon this article which clearly expands on the difference between TG and EE fish oil forms.

  • Donald Kjellberg

    2/3/2011 6:09:27 AM |

    Rick said...
    "Just to check: Are triglyceride forms always in bottles? Or can we also get them in capsules?"

    To say it lightly, I prefer to get them off the back of my fish like wild caught salmon but especially with sardines like Ned referred to since the mercury content is extremely low to nonexistent.

    Also, it may be more beneficial consuming supplements naturally in whole foods, if you can get enough. That in itself is not an easy endeavor. Don't get me wrong, I do take my fish oil capsules especially when consuming high 6:3 ratio foods but am trying to incorporate more nutrient dense foods that contain known rich supplement content.

    It would be nice to see more research addressing synergistic effects of nutrients in foods like Dr. Price's findings regarding fermented cod liver oil and high vitamin butter oil.

  • Dr. William Davis

    2/3/2011 3:02:12 PM |

    Hi, Jack--

    No, not even close.

    It also depends on why you take fish oil and/or obtain omega-3 fatty acids and whether or not you have coronary atherosclerotic plaque, among other things.

  • Jack

    2/3/2011 3:16:28 PM |

    The only brand of canned salmon/tuna and canned sardines I eat is from Wild Planet. I am not affiliated with them and this is not an advertisement, but they really seem to do the whole process perfectly. They also do not add any vegetable oil or water. They have very low mercury content and very high natural omega-3 content. The omega-3 in their tuna is even higher than the salmon. Also, they explain the importance of low mercury and how it all works.

    Have a look at their site:

    Wild Planet

    Jack Kronk

  • Davide Palmer

    2/3/2011 4:34:05 PM |

    I often wonder if krill oil is an even more superior source of DHA and EPA simply because they come within the matrix of phospholipids. Phospholipids, of course, are what makes up our cell membranes, making krill oil extremely bio-available to the cells. I guess we will have to wait for tests to confirm.

  • Sara

    2/3/2011 7:11:36 PM |

    The triglyceride form is too expensive for me.
    I'll pop an add'l ethyl ester gelcap daily and be done with it.

  • Rick

    2/3/2011 10:06:10 PM |

    Does the same caveat apply to krill oil or to seal oil?

  • Anonymous

    2/4/2011 1:35:33 PM |

    Great Detailed discussion of fish oil
    Can someone please dumb it down for me and just recommend a few brands?

  • John Townsend

    2/4/2011 7:17:46 PM |

    Dr. Davis:

    I'm curious to know where GNC's so-called "Triple Strength Fish Oil"
    product ranks. It comes in a softgel form, each capsule containing EPA+DHA strength of 900mg. It has only a slight hint of fishy-ness in taste. It's not clear to me from the bottle label whether it's in a triglyceride form. I'm not necessarily an advocate of GNC products which are not generally a bargain by any means, but have been satisfied with their quality.

  • Timothy Johanek

    2/5/2011 3:24:53 PM |

    I am a Technical Representative from Carlson and the following fish oils are all TG or rTG form:

    -EPA Gems

    -Super DHA Gems

    -MedOmega Fish Oil 2800

    -All Mothers and Kids products

    -All Very Finest Fish Oil products

    -All Cod Liver Oil products

    -All Salmon Oil products

    -Smart Catch softgels

    -CalaOmega liquid (calamari oil)

    The following products are EE:

    -Super Omega-3 Gems

    -Elite Omega-3 Gems

    -CalaOmega Softgels (calamari oil)

    -CalaDHA Sofgels (calamari oil)

  • Anonymous

    2/6/2011 2:08:07 PM |

    "struggle with high TG, now 292 even with fish oil and 1 gram a day of IR niacin... "

    1grm just is not high enough in my opinion.  I take 2grms of Now brand Niacin and had a 30% reduction in my Trigs. At C$7 for 100 x 500mg tablets it is a cheap treatment. somewhere between 2-3grms is the level required but you can check studies at

    btw.  just wanted to announce that my latest HDL is 50 !  I started with a reading of 28 and had been on a low fat no meat diet for years. Added meat, reduced wheat and other grains over the last 6 months. I guess I am a convert.

  • omega3tron

    2/6/2011 7:28:10 PM |

    It is nothing more than just another market gimmick -

  • Bob Savage

    2/6/2011 7:59:46 PM |

    Timothy Johanek,  Do you have any reference to independent test that proof Carlson's products in TG/rTG form?

  • Anonymous

    2/7/2011 5:31:15 PM |

    I'm also interested if Dr. Davis can comment here or in one of his articles about the proper dosing for Apo 3/4 people.

    I do notice that lowish doses (1 g or less) doesn't seem to affect my LDL much negatively. However, if I go high, say 3g EPA/DHA or so, then my LDL tends to rise... and it's not the particle size thing giving a false high reading, as it's measured by VAP.

    Somewhat oddly, I have noticed that the EE form causes this rise more often than the TG form, but that could be coincidence.

    And for those interested:

    Barleans (orange, low dose): TG
    (high dose): EE
    Minami (EE, except for MarineEPA)
    Nordic Naturals: rTG
    Meg3: Can be either, but unless specified, it's EE
    Epax: rTG
    Carlson has both forms, as mentioned here
    Coromega (rTG Epax oil (I think))
    Natural Factors: EE

    And pretty much all cheapo store brands are EE.

    Krill oil does absorb better than fish oil, as found in a recent study. However, it's like a 50% or so improvement only (at best), and due to price differences between fish/krill, it doesn't make much economical sense. If the esterified astaxanthin provides a specific benefit, then maybe it's worth it... but no data showing it's the EPA/DHA in krill.

  • Weierstrass

    2/9/2011 5:01:13 AM |

    That's good news on the Carlson's. I really don't understand why anyone uses fish oil capsules. You get a much better deal with the fish oil in bottles; I order mine online, 4 or 5 bottles at a time.

  • Anonymous

    2/9/2011 1:09:17 PM |

    Which brands of Fish Oils doesn't use Soy Bean oil?

  • Timothy Johanek

    2/9/2011 10:46:31 PM |

    Bob Savage,

    I'm not aware of any third party tests that have been done.  I am certain that I am correct though because I write the spec sheets.

    A quick test to see whether an oil is EE or not is to put it on polystyrene (styrofoam) because EE will dissolve it but TG will not.  And before anyone gets nervous, this has nothing to do with how EE oils affect your body (unless you eat or are made of styrofoam that is).

  • farseas

    2/21/2011 6:29:36 PM |

    Hi readers.  With all this talk about O3 and fish oil I thought that I would chime in with my experience.  I had a heart attack about 1.5 years ago and got a stent placed in one of my arteries.

    Since then I have been taking Walmart fish oil because it was so cheap.  My chest pains gradually receded after my heart attack and I was doing really great for awhile.  I was actually working pretty hard, doing aerobics for about 30 minutes and lifting weights for about 20 minutes.  My weight on a low carb diet went from 305 to 260 so far.

    I have been on Plavix but my cardiologist told me I could back off from it slowly, so I started taking 6 capsules of Walmart fish oil, 400mg VE, 1000 mg VC, 325 mg aspirin, and only half a 75 mg Plavix.

    Then, I went to Walmart and got a new supply of fish oil.  Upon taking it I started to get pretty strong chest pains and had to stop working out.  I did not associate the problem with the fish oil though.

    One day I came to this blog and read about rancidity in fish oil.  I broke open one of the fish oil caps from Walmart and was overwhelmed by the spoiled fish smell.  I immediately stopped taking the oil and my chest pains gradually diminished.

    My question is whether I am likely right that it was the oxidized fish oil causing the chest pains?  This wasn't a very rigorously controlled experiment. I am not looking for an absolute answer but is it possible that rancid fish oil can cause chest pains?

  • Anonymous

    2/23/2011 12:56:27 PM |

    Farseas that is very interesting. Glad to hear you have been doing better.

    in for answer on rancid oil.

    I've been using Ascenta fish oil. They're based out of nova scotia. All their oils are in triglyceride form. can be found much cheaper elsewhere like

  • Anonymous

    2/23/2011 12:56:39 PM |

    Farseas that is very interesting. Glad to hear you have been doing better.

    in for answer on rancid oil.

    I've been using Ascenta fish oil. They're based out of nova scotia. All their oils are in triglyceride form. can be found much cheaper elsewhere like

  • Anonymous

    2/25/2011 10:30:39 AM |

    Should we worry about this?
    Fish Oil Increases Risk of Colitis, Colon Cancer in Mice

  • john

    4/9/2011 6:49:51 AM |

    Thank you so much for the post. Fish oil is best for our health.This is very informative blog.
    -fish oil

  • Gailtoo

    4/27/2013 1:19:39 PM |

    Personally, I don't put a lot of faith in studies done on mice. Their biological makeup is different than ours and these studies often give mice mega-doses of whatever they are testing for over very short periods of time, which could have adverse consequences for anyone. I like human trials better.