Fish oil: What's the difference?

Ultra-purified, pharmaceutical grade, molecularly distilled. Over-the-counter vs. prescription. Gelcap, liquid, emulsion.

There's a mind-boggling variety of choices in fish oil today. A visit to any health food store, or any "big box" store for that matter, will yield at least several, if not dozens, of choices, all with varying and often extravagant claims of purity and potency.

So what's the real story?

Given the analyses conducted over the years, along with my experience with dozens of different preparations, I believe that several conclusions can be reached about fish oil:

Fish oil is free of contamination with mercury, dioxin, PCBs, or furans. To my knowledge, only one fish oil preparation has been found to have a slight excess of PCBs. (This is different from cod liver oil that has been found by one source to have a slight excess of PCBs.)

Oxidative breakdown products differ among the various brands. Consumer Lab (, for instance, has found that several widely available brands of fish oil contained excessive oxidative breakdown products (TOTOX). You can perform you own simple test of oxidative breakdown products: Sniff it. Your fish oil should pass the "sniff test." High quality fish oil should smell non-fishy to lightly fishy. Rancid fish oil with excessive quantities of oxidative breakdown products will smell nasty fishy.

FDA approval does not necessarily mean greater potency, purity, or effectiveness. It just means that somebody assembled the hundreds of millions of dollars to obtain FDA approval, followed by lots of marketing savvy to squash the competition.

This means that there are a number of excellent fish oil products available. My favorites are the liquid fish oils from Pharmax, Nordic Naturals, and Barleans. Capsules from Carlson, PharmaNutrients, and Fisol have also performed consistently. The "big box" capsules from Sam's Club and Costco have also performed well and are wonderfully affordable.

Comments (27) -

  • Bill Millan

    12/10/2010 3:01:47 PM |

    I have engaged in more discussion about fish oil than any other supplement. Just remember we could care less about the fish oil, what we are after is the EPA+DHA Omega 3 in the oil. The rule of thumb is, "the higher the price, the more Omega 3." You can save money and get the 30% in the Kirkland or Sam's Club brand or spend a lot more money and get the 50% to 70% brands.

  • Bill Millan

    12/10/2010 3:01:47 PM |

    I have engaged in more discussion about fish oil than any other supplement. Just remember we could care less about the fish oil, what we are after is the EPA+DHA Omega 3 in the oil. The rule of thumb is, "the higher the price, the more Omega 3." You can save money and get the 30% in the Kirkland or Sam's Club brand or spend a lot more money and get the 50% to 70% brands.

  • arnoud

    12/10/2010 3:11:11 PM |

    Often I have wondered about the benefits, if any, of krill oil versus regular fish oil.    
    It seems that the Phospholipids in the Krill oil play a role in HDL quality.

    I have not yet found a good paper explaining this, but Neptune Technologies is doing some research on this.  I prefer whole foods, rather than drugs, but the research on this topic looks interesting.

    From their website on a research on concentrated phospholipids form krill oil:
    Neptune Technologies & Bioressources Inc. Reports Completion of Acasti Pharma Comparative Benchmarking Program versus Lovaza®

    Laval, Québec, CANADA – November 25, 2010 – Neptune Technologies & Bioressources Inc. (“Neptune”) (NASDAQ: NEPT - TSX.V: NTB) subsidiary, Acasti Pharma Inc. (“Acasti”), reports the completion of its  preclinical program designed to compare the lipid management effects of Acasti’s drug candidate CaPreâ„¢ versus prescription drug Lovaza®.  Blood lipids were monitored in two animal models in order to assess and compare the efficacy of CaPreâ„¢ and Lovaza® over a 12-week treatment period.

        * A low daily human equivalent dose of 1g CaPreâ„¢ reduced LDL-C (bad cholesterol) levels by 40% and increased HDL-C (good cholesterol) by 180% in a normal rat model (“SD”) while 4gr of Lovaza® did not show any significant effect.
        * An even lower daily human equivalent dose of 0.5g CaPreâ„¢ was shown to be as efficient as 4g of Lovaza® in reducing triglycerides levels by 40-50% in obese rats with severe diabetes and high triglycerides (“ZDF”)

    “These results suggest that a low (0.5g to 1g) daily dosing of CaPreâ„¢ is more effective than 4g Lovaza® in elevating HDL-C and lowering LDL-C and triglycerides.  These effects become even more striking considering that a 1g daily dose of CaPreâ„¢ contains 8.9 times less EPA and 11.1 times less DHA than the recommended 4g daily dose of Lovaza®. It is also important to note that the triglycerides reduction was observed only after 4 weeks and was maintained throughout the study suggesting a significant metabolic impact of CaPreâ„¢,” said Dr. Bruno Battistini, Senior Director, Pharmaceutical R&D of Acasti.

  • Geoffrey Levens

    12/10/2010 4:38:02 PM |

    If one brand showed slight excess of PCB's, does that mean all the rest also contained PCB's only just the right amount?

    What are the benefits to cardiovascular health of taking plant/algae sourced DHA vs fish sourced EPA/DHA?

  • Anonymous

    12/10/2010 4:54:31 PM |

    What do you think of the conclusions in this blog post?

    For a "healthy" person are your recommendations the same- as in make sure to get a high quality fish oil?

    I really appreciate you taking the time to write on this blog.  Thank you!

  • Jack

    12/10/2010 5:00:58 PM |

    or you could just eat natural food sources of omega-3, like wild salmon, tuna, sardines, grass fed butter, eggs from pastured chickens, fermented cod liver oil. then you wont need supplements.

    jack k

  • Eric

    12/10/2010 5:20:40 PM |

    What if you can't stand the taste of fish like salmon and sardines or fermented cod liver oil?

    I'm hoping Carlsson's is good, that's what I've been taking for the past few months and I love how it tastes like lemon oil, not fishy at all.

  • Dr. William Davis

    12/10/2010 7:48:29 PM |

    While there is debate on the reduction in cardiovascular events with omega-3 fatty acids, I use them to achieve correction of a number of physiologic parameters:

    1) Reduction of triglycerides
    2) Acceleration of clearance of postprandial lipoproteins, such as chylomicrons, chylomicron remnants, and VLDL
    3) Reduction of lipoprotein(a)

    The data on the likelihood of cardiovascular mortality correlates inversely with RBC omega-3 EPA + DHA; the relationship is quite strong. While we lack prospective trials outside of GISSI Prevenzione on the reduction of cardiovascular death with higher levels, given the overall improved surrogate measures of risk, I believe that the data overall are sufficiently compelling.

  • Anonymous

    12/10/2010 8:49:01 PM |

    Funny, I've been reading up about this lately. I like the fact that if we can - there is the possibility of actualy getting the appropriate amount of EPA+DHA Omega 3's by eating fish. I recently started buying sardines just for this purpose and I'm going to try real hard to incorporate oily fishes. I like it when people help others minimize the amounts of supplements they use.

  • Anonymous

    12/10/2010 10:03:22 PM |

    dr. davis

    i can't smell anything rancid in my distilled fish oil with orange flavour but its so weird its too heavy barely digests and stays as if stuck in the chest. feels horrible.

    not sure what to make of it.

  • Pater_Fortunatos

    12/10/2010 10:07:40 PM |

    There are a few benefits of a plant based diet: avoiding acid load, toxin accumulation in the food chain, and another one, high lipid peroxidation level of the longer chain EFA.
    So I just heard that "Reduction of triglycerides" using fish oil, is an effect of liver damage.

    Just search for this book:
    "Fatty acids in foods and their health implications" - Ching Kuang Chow
    I just quote from the chapter V. MEMBRANE UNSATURATION AND LONGEVITY
    In summary, the above mentioned studies provide a correlation between the maximum longevity of animals and the degree of unsaturation of membrane fatty acids. That correlation joins the previously stated one between the rate of mitochondrial oxygen radical generation and the maximum
    longevity of animals. In long-lived homeothermic vertebrates, both free-radical production and the
    membrane fatty acid unsaturation are lower, offering an explanation for some of the main causes of
    the low aging rate peculiar to these animals. No studies have been carried out on these aspects in
    relation to dietary fat and, as it will be stated below, this is another notable aspect of fatty acids and

  • John

    12/11/2010 2:35:55 AM |

    Is there an over-the-counter brand of fish oil that closely matches prescription Lovaza?

  • Jack M.

    12/11/2010 3:37:59 AM | has very informative articles on this. Type "cod liver oil" in the search box to find their articles.  There is great info on how the better brands are manufactured.

  • William Trumbower

    12/11/2010 3:24:04 PM |

    A product similar in principal to krill oil is Vectomega.  It is a phospholipid bound salmon oil made from salmon heads.  The heads used to be discarded and this is a resource that doesn't deplete the food of whales etc.  According to the companies data, one tablet is the equivalent of eight standard capsules (probably 2.4gm of EPA+DHA).  It is a little pricey, but you will never burp it and it is very portable when you travel.  I suggest to my patients that if they regularly take much more than 2.5gm, that they get AA/EPA ratio available thru many labs.,

  • Geoffrey Levens

    12/11/2010 4:57:33 PM |

    Supposedly DHA converts in the body to EPA pretty easily.  Anyone know any data about taking DHA alone vs with EPA?

  • Vlado

    12/11/2010 5:36:56 PM |

    to come from other side, I have started to read Ray Peat's articles and he is big on the dangers and overhype of non saturated fatty acids , in particular omega 3. It makes sense that humans having developed in hot climate require primarily saturated fat to protect from heat, light and oxygen. There is a reason why fish oils smell and why vegetable oils must be deodorized, it's basically our body telling us that non saturated oils are bad for us. Ray Peat says these oils make our membranes "floppy" and our skin prone to photo dammage by the sun. Basically we need all the saturated fat we can get primarily from coconut oil and butter but polyunsaturated fats should be minimum and certainly no supplement. Read up here

  • Anonymous

    12/11/2010 6:57:14 PM |

    I take at least 900 EPA + 600 DHA fish oil daily. I usually take 1-2 softgels with each meal. I continue to experiment with higher doses, but so far, I can't tell the difference between 5 softgels daily vs 10 softgels daily except 10 softgels means 50 extra calories. Sometimes I actually need extra calories, so I've taken as much as 40 softgels in one day.

  • rhc

    12/12/2010 2:30:31 AM |

    I guess I'm the only one who actually LIKES chewing my fishoil capsules. To me they are like a treat! This has the added advantage of knowing for sure if they are rancid. I've been getting Sundown Naturals for over a year - never had a bad one yet. The taste is very mild and I they never make me burp.

  • Anonymous

    12/12/2010 2:53:27 PM |

    dr. davis i d like to know your take on this

  • Travis Culp

    12/12/2010 7:27:04 PM |

    I've found that Barlean's cod liver oil is least offensive taste-wise, followed by Spectrum. Both are molecularly distilled. I have trouble finding Barlean's, however.

  • Anonymous

    12/12/2010 9:45:55 PM |

    In declaring EPA and DHA to be safe, the FDA neglected to evaluate their antithyroid, immunosuppressive, lipid peroxidative (Song et al., 2000), light sensitizing, and antimitochondrial effects, their depression of glucose oxidation (Delarue et al., 2003), and their contribution to metastatic cancer (Klieveri, et al., 2000), lipofuscinosis and liver damage, among other problems.

  • Anonymous

    12/13/2010 4:56:56 PM |

    Dr. Davis,

    Should Vitamin D gelcaps have an odor? I've been taking a generic drugstore brand and they always have an unpleasant smell, but I assumed they were supposed to.


  • Vin

    12/13/2010 7:29:14 PM |

    @arnoud - phospholipid-bound Omega-3 appear to get incorporated into membranes 1.5 to 2X more than triglyceride or ethyl ester Omega-3. But Neptune researchers have not explained why krill oil reduces LDL more than Lovaza.

    @Geoffrey Levens - just about every food product has small amounts of PCBs. Yes, fish oil too. Cod and Shark liver oils typically have much higher levels. More on fish oil and PCBs here.

    Retroconversion of DHA to EPA is not very efficient. Roughly 10% of DHA gets converted to EPA. EPA to DHA far less efficient. Several metabolic factors affect these conversions. Bruce Holub at Univ Guelph has done great work on this. Check out PMID: 9507234 and 9076673.

    @John - Several brands have 700 - 900 mg Omega-3 per pill, like Lovaza.

    A few have 20-30% more Omega-3 than Lovaza:
    Minami Nutrition CardiO3
    Ocean Blue Professional
    RenewLife come to mind.

    These all have over 1000 mg Omega-3 per pill.

    Next-gen fish oil (pipeline) drugs like Epanova and AMR101 are mostly EPA - so worth looking into high EPA OTC formulas for a fraction of the price.

  • Kevin

    12/14/2010 12:05:36 AM |

    $2000 per month doesn't seem so bad.  For the three of us, two adults and one 18yr old, we pay $2600 per month.  But my wife had cancer twice:  Hodgkins Lymphoma 24 years ago and breast cancer six years ago.  Before doing anything that might be dangerous, I remind myself of the $1500 deductable.  


  • Anonymous

    12/15/2010 8:27:27 AM |

    dr. davis

    i did some research and to answer my own question on fish oil...
    for those without heart disease (like me) 1 gram of fish oil is sufficient and should be taken with 4 grams of saturated fat otherwise fish oil slips through the intestines undigested. 4 grams of saturated fat is used for making the liver start bile production.

    original question

    dr. davis

    i can't smell anything rancid in my distilled fish oil with orange flavour but its so weird its too heavy barely digests and stays as if stuck in the chest. feels horrible.

    not sure what to make of it.

  • Buy Resveratrol

    1/13/2011 9:41:21 AM |

    It is good; however the oil came from the liver. It can contain too much Vitamin A and it could be dangerous if u overdose. I suggest sticking with eating a variety of fish.

  • Anonymous

    2/12/2011 10:33:52 PM |

    ah great info.......i live in the UK and I usually take different supplements, plz cud u tell me what should i look for while buying the fish oil....tnx in advance Smile