What Is The Best Cod Liver Oil?

Cod liver oil is the most popular health supplement, and as a result of this many companies are manufacturing their own brands and trying to make a cheaper and...

Cod liver oil is the most popular health supplement, and as a result of this many companies are manufacturing their own brands and trying to make a cheaper and more affordable product. By reducing production costs the resulting product is often poor quality, but do you know the difference between quality and price? This article will explain how cod liver oil is made, and how to identify the best cod liver oil.


It starts with the fish

As with all nutritional products, the final product cannot be any healthier than the raw materials they are made from, which in this case are cods livers. Livers can be sourced from either farmed fish or wild fish, and the quality of the liver differs greatly between the two sources. Farmed fish are fed a diet derived from fish meal, vegetable oils and plant matter, which is often made from waste materials from the food industry. These foods are often low in micro-nutrients and the feed is tailored to the macro-nutrient requirements of the fish, not the micro-nutrients. This often results in cod with poor health, with low levels of omega-3 fatty acids in their liver, and a higher than normal level of heavy metals in their body such as methyl-mercury and cadmium. Farmed fish are very cheaply sourced, which reduces the cost of production, but the presence of heavy metals and low omega-3 content reduces the quality and nutritional value.

Wild fish, which are able to eat their natural diet are much lower in toxins, and the omega-3 content of their liver is much higher than farmed fish. They are able to exercise more as they are not enclosed, and must catch their food, which means that they will not contain any undesirable fatty deposits in their liver.  Oil obtained from these fish is much more nutritious, and so a good cod liver oil supplement will be made from these fish.


How cod liver oil is extracted


Wet processing Wet Processing - The Best Cod Liver Oil?

This is a very commonly used extraction method, and produces both fish oil and fish-meal. A diagram showing the stages of wet processing can be seen on the right. From the diagram you can see that there is a cooking stage and a pressing stage which greatly impacts the quality of the oil. The high heat (up 95 degrees) and pressure creates a highly reactive environment, which rapidly oxidizes essential fats with oxygen which is present in the air, rendering them nutritionally useless and toxic. The optional carbon treatment stage is used to remove harmful chemicals (such as heavy metals) from the oil, but can also remove vitamin A and D too.  If farmed fish are used to produce this oil, then it is important that the carbon treatment is carried out to remove the high levels of toxins. Often synthetic versions of vitamin A and D are added to the oil if it has been carbon treated, which are less bio available than the naturally occurring vitamins.

This is not an ideal treatment method, because it damages a the essential omega-3 fatty acids, and can remove the naturally occurring vitamin D and A.Enzymic Hydrolysis - The Best Cod Liver Oil?


Enzymic hydrolysis

This method is not commonly used as it is not economical. It uses naturally occurring enzymes to break down the liver cells and release the oil. The pasteurization stage at the start can cause oxidation of the fatty acids in a similar way to that of high pressure and heat, but to a lesser extent. Fish oil extracted via this method will contain naturally occurring vitamin D and D, which makes this oil more desirable than wet processed oil.



Dry Rendering - The Best Cod Liver Oil?

Dry rendering

A similar method to wet processing, dry rendering includes cooking and pressing stages which cause damage to the omega-3 fatty acids. This method producesa product called ‘crude fish oil’, which needs to go further cleaning before it can be used, this cleaning process can further damage vitamins and omega-3 fatty acids, and there are various methods by which it can be cleaned. This is not a particularly popular method, as it can be expensive to conduct.


Acid-alkali process

This method is similar to enzymic hydrolysis, but instead of using enzymes to break down the proteins variations in pHs are used, which makes the process Acid-Alkali - The Best Cod Liver Oil?easier to control. As there is no heat or pressure used in this method, it is more desirable than the previous 3 methods discussed as there is minimal damage to the fatty acids from oxidation. The varying pH will cause minimal damage to the omega-3s, but will do more damage to vitamin A and D, meaning that synthetic vitamins are often added to the oil afterwards.


Salt water fermentation

Salt water fermentation is the traditional method for fish oil extraction, and involves adding ground cod liver to a barrel with sea water for an extended period of time. The liver cells are broken down by bacteria, which releases the oil ready for processing. As no heat, pressure or extreme pHs are used in this method, the omega-3s and vitamins are undamaged. The bacteria which break down the liver cell walls produce other co-factors, in particular co-enzyme Q10 (ubiquinone), which is present in the  final product, and is known for its benefits for the cardiovascular system. This process can take up to a year to complete, which adds to the production costs, but preserves all the nutritional content of the oil.


What Is The Best Cod Liver Oil?

Image Courtesy of MyDigitalSLRCamera

Synthetic vitamins vs naturally occurring vitamins

Vitamins which are produced naturally are often found with various metabolites of the vitamins, which aid with its absorption and utilization in the body. This is similar to the way vitamin C is often blended with bioflavinoids, as they help the body absorb and use vitamin C. Synthetic vitamins do not come with these metabolites, and can also be bonded to other molecules to help stabilize or extract them, which makes them harder to absorb and utilize in the body. Some synthetic vitamins have actually been shown to be toxic because of they way they have been stabilized. This means that a cod liver oil which contains contains vitamins in their natural form are much more desirable and hold more nutritional value than cod liver oil supplements which have had synthetic forms added.


Storage and container

Once the cod liver oil is made into a supplement form and encased inside a gel capsule, it is still vulnerable to oxidative damage. Exposure to UV light, or pending a prolonged time in a warm environment will cause oxidation of the omega-3 fatty acids. This is very slow, but over a long period of time the damage builds up. this is why it is important to ensure that cod liver oil capsules are contained in a dark bottle which UV light cannot penetrate, and kept in a cool place, ideally a refrigerator.



The best cod liver oil will be sourced from wild fish and contain vitamin A and D in their naturally occurring form, as this ensures the body can absorb them and utilize them efficiently. It is also important to ensure that the omega-3s are not damaged during the extraction process, as this will render them nutritionally useless. The fermentation process provides additional nutrients such as co-enzyme Q10 (ubiquinone) which offer additional health benefits, and also doesn’t cause oxidative damage to the omega-3s. To prove quality, some manufacturers have their products independently tested for content of omega-3s vitamin A and D and ubiquinone to show they are present in sufficient quantities. If a manufacturer doesn’t make independent quality tests public, it is an indication that their product is not high quality.

I hope you enjoy the site, and like what we have worked hard to create, any feedback is very much welcome, after all this site is for you! Graduate of Nutrition & Food Science (Bsc) at Reading Uni.
    • Jen

      Are you allowed to talk brand names? I would really like to know. Thanks!

      • Craig

        Hi Jen,

        Yes we are allowed to talk brands (although we will remove any spam comments which are clearly just brand promotion).

        I have avoided talking about brands in the article to avoid any bias. I wanted the article to be informative, and not an advert. Feel free to discuss brands in the comments or on our forum though 🙂

    • Matt

      Hello Craig
      Thanks for the website info.
      Could you suggest a couple of brands that use the good quality cod liver oil, there are so many out there!……thank you.

      • Craig

        Hi Mat, glad you like the info! 🙂

        There is only one brand which sells fermented cod liver oil, which is Green Pastures (although another brand will be coming out soonish). Fermented cod liver oil is the best quality out of them all, and Green Pastures have their product independently tested for purity, quantity of nutrients and amount of toxins (which you can see here– you can’t beat that really!

        • Matt Anker

          Hello Craig.
          Just a quick ‘thank you’ for the extra info and prompt response! Very useful.

    • Jen


    • Ben

      Great stuff, Craig. Also backs up the fascinating work currently being done by Ramiel Nagel.

      • Craig

        Cheers Ben 🙂

    • Jason

      Hi Craig,

      You have mentioned the Green Pastures CLO which is clearly the best on the market but which comes with a steep price tag. Can you perhaps suggest an alternative CLO which offers similar benefits at a lower price tag and which is available in the UK?


      • Craig

        Hi Jason,

        Unfortunately, Green Pastures is the only fermented cod liver oil I am aware of. You are right, about the price, and it is very annoying. I can only think the price is due to the costs of wild cod fishing, long processing periods, being an exclusive product, testing for toxins/ purity and importing it from the states. I would like to see a comparable competitor come to the market which is made in Europe. I did white a blog post about cod liver oil prices ages ago which you might find useful: http://www.blog.thehealthcloud.co.uk/2012/11/why-does-cod-liver-oil-vary-in-price.html

        Not cutting corners in production makes a great and nutritious product, but the problem is that it does come with a premium price…

        If you are looking for an EPA and DHA supplement (green pastures contains many nutritious metabolites in addition to EPA and DHA), then there are a number of alternatives. I would suggest that you make sure that it is from a reputable brand, tested for purity, and if possible, is made with triglycerides and not ethyl esters.

        If you like, you can post specific products in the comments here and I will have a look at them for you 🙂

        • gabs67

          Hi Craig,
          concerning other valid alternatives, what do you think of Extra Virgin Cod Liver Oil (EVCLO) produced by Rosita Real Foods in Norway?
          Thanks for your advise!

          • Hi Gabs67.

            In one of my previous comments I did mention that a new brand is coming out which is comparable to green pastures, and this is that brand!

            From what I know about the product, it certainly is comparable in quality to Green Pasutures, although also comes with a hefty price tag.

            On a personal note (and it is just that), I’m not a big fan of the company behind EVCLO. I don’t like the way its marketing strategy seems to be focused on making Green Pastures cod liver oil look bad, and even goes as far as making blatent lies about Green Pastures (such as its sourced from China!). I think a product should be sold on its merits, not spreading lies and rumours about a competitor.

            I did like EVLO when it was in production, and we wanted to stock it in our shop! Its the attitude of the company which has put me off them. Shame really.

            • gabs67

              Hi again Craig,

              Yes, I agree: a company that relies and believe in its products shouldn’t need to go that path…
              Nevertheless as a “standard consumer” it is really difficult to have a clear idea about oil from fermented cod liver…
              Especially if you read a comment at the bottom of following article

              Where somebody says:
              “We ordered a bottle of fermented cod liver oil and had it analyzed by an independent company in Norway. The oxidation level was in the toxic range and it was also likely contaminated by blood protein.
              This product has nothing to do with health and well-being unless you believe that eating old and rotten fish is good for you.” – Bo Martinsen, MD

              Then you think: “God am I really doing the right thing taking those pills? ”
              This shouldn’t just be a matter of “what is good for one is bad for another one”! I need, we all do need it to be medically ascertained.

            • Gabs67, this is the exact thing I mean about EVCLO slating Green Pastures. If indeed the Green Pastures product has been independently tested, where are the published results? That comment is a clear attack at Green Pastures, with no actual evidence…

              Green pastures have their products independently tested, and make all the testing of their products public, you can see the link of the testing in their section here: https://www.thehealthcloud.co.uk/fish-oil-showdown/

              I’m not saying that the commenter is indeed working for EVCLO, but unsupported comments like that stink of underhand marketing.

              Assuming for a moment that this comment is true (which I suspect it isn’t), read the comments in response to it. Furthermore, have a look online about all the benefits of Green Pasutres that members of the general public report (over many years). I really doubt that these benefits are due to toxic oxidation levels and blood protein contamination….

              Sorry, but without some real proof that Green Pastures is toxic, I will still recommend it. The evidence for its benefits is overwhelming.

            • gabs67

              Yes, what you say makes sense, actually.
              Thanks for your time and the useful information in your site, Craig

    • Due to many requests for me to mention brands, I have written a post comparing several brands to show you just what to look for in a cod liver oil/ fish oil. I look at sourcing, omega-3 format, dosage, vitamin content etc. Hopefully this should answer any further questions 🙂


    • Tonyhathaway

      Thanks for this. The results of all your hard work are very useful and much appreciated e

    The Health Cloud was created in December 2011 by Craig and Morg who have been friends since high school. Our focus is to educate our readers with unbiased health articles and on the side we run our own online health shop. This website is for you, so drop us a comment or send us a tweet, we always take the time to reply!