News & Updates

How major brands make cod liver oil

By Dan Corrigan   ∙   October 06, 2020   ∙   0 Comments
The Rosita production method vs. the standard production of cod liver oil

Rosita® is the world’s only fresh, wild-caught, raw cod liver oil. This means it’s completely unprocessed. To understand Rosita®’s purity, our customers often ask us what the standard process used by major brands is like. 

Largely unknown to the public is that the major brand cod liver oils go through a battery of processing steps involving high heat, high pressure, vacuums, solvents, moisture and chemicals. 

The fragile omega-3 fatty acids are heated so high, in some cases, that trans fats are formed, which remain in the oil. Heavy metals and other contaminants from fish sources in polluted waters, and toxins formed due to improper handling, long-term storage, and exposure to heat and oxygen, must be “cleared” from the oil before bottling. These highly refined processing steps are designed to create an easy-pouring, shelf-stable cod liver oil for the masses.

However, the processing steps create additional harmful substances, for which more heat and solvents are required.

Each step further weakens the integrity and nutritional value of the oil. Most of the popular cod liver oil brands are purified to the point where the natural vitamin A and vitamin D3 are damaged or completely destroyed.

Here’s a step-by-step rundown of each step based on extensive research of cod liver oil processing and the marketplace (see sourcing below). Please note that some of the steps may be slightly different, optional or combined, depending on the manufacturer (For instance, a couple of brands do not fortify their oils, so the processed final products are inherently low in vitamins). 

  • Alkali refining: Removes free fatty acids.
  • Bleaching: As cod liver oil loses its freshness (which happens quickly) the oil goes from a beautiful pale golden color to being cloudy and murky. Eventually, the oil turns brown. Bleaching removes the color substances and the oil is once again clear in appearance.
  • Winterization: Removes saturated fats and stearin (which solidify when refrigerated).
  • Deodorization: A steam stripping process wherein steam is injected into oil under low pressure and high temperature to vaporize the Free Fatty Acid (FFA) and eliminate the oil’s odor. 
  • Molecular distillation: This means boiling the oil to over 375℉, which removes pesticides, PCBs and much of the vitamin and nutrient content. 
  • Addition of synthetic and “natural” vitamins: Most cod liver oil producers will add vitamin D3 from lanolin to compensate for the vitamin D3 destroyed in processing. The lanolin is separated from wool fat, purified and exposed to ultraviolet B (UVB) radiation. Some manufacturers will also add synthetic vitamin A to make up for the vitamin A destroyed in processing. The addition of synthetic and natural vitamins does not have the same ratios and synergistic healing effects of the vitamins naturally found in pure cod liver oil.
  • Addition of synthetic and/or highly processed antioxidants: Since cod liver oil does not have enough naturally occurring antioxidants it is necessary to add antioxidants. The quality of the antioxidants varies greatly.
  • Addition of synthetic flavors: Artificial mint, strawberry, lemon or other flavors are added to completely mask the taste of fish. So-called natural flavorings are not derived from the actual berry, fruit or mint leaf but rather from ingredients that create an aroma perceived as natural.

More detail about each step in the standard process used by major brands


Sourcing the fish: Depending on the producer, commercial cod liver oil could come from actual wild-caught cod, or it could come from pollock or haddock (sourced from Alaska and/or Russia) or other fish species, both wild-caught and farmed. The international production of cod liver oil is regulated by only one rule — the final product must match the specific EPA/DHA ratio found in raw cod liver oil. Cod liver oil has about 9% EPA and 14% DHA, whereas fish oil generally contains about 18% EPA and 12% DHA. Cheaper oils are often added to achieve the correct EPA/DHA balance. Regardless of the country of origin, the oil is then bottled and sold as true Norwegian or Arctic cod liver oil.

Cod liver oil extraction: Wild cod are caught in large trawlers that spend weeks at sea. In the best scenario, the fish are harvested at sea, and the livers are collected and transported to the rendering plant. At worst, the livers are collected and stored aboard the ship for long periods, where they start to degrade in quality. Upon arrival at the processing facility, the livers are ground up and then either heated for a length of time or cold pressed mechanically to extract the oil. The remaining liver mass is then heated and put through a decanter to remove solid parts. Then it’s centrifuged, separating the liver mass into crude oil, water and sludge. At this point, the crude oil intended for human consumption is further processed, while the residues are dried to produce liver meal to be sold as fish and animal feed. Most cod liver meal is shipped to Southeast Asia for the shrimp feed industry. The idea that cold-pressed cod liver oil is somehow raw or gently processed compared to heat rendering is a marketing ploy. Cold pressing refers to the extraction of the oil from the liver. Once extracted, however, the oil is subjected to high heat during the degumming (212℉), deodorization (374℉ or higher), and molecular distillation (375℉) steps.

Carbon Treatments: Carbon treatments are used on the initial crude oil to remove dioxins, furans, and polyaromatic hydrocarbons (PAH), which are toxic. The European Union recommends the reduction of dioxins, furans and PCBs in feed and food. It sets out action levels for certain food sources, including farmed fish, to encourage member states to proactively reduce dioxin levels. When these contaminants occur in wild-caught fish, the reason is environmental pollution rather than a point source. Therefore, no action levels have been set for wild-caught fish. Generally, carbon treatment is necessary for farmed fish and fish caught near industrial areas.

Degumming: The crude oil is hydrated, heated to 212℉, and treated with phosphoric acid to separate the phospholipids, resins, proteins, minerals, and other materials intrinsic to cod liver oil. The main reason for the removal of phospholipids is that some of the compounds, particularly the calcium and magnesium salt of phosphatidic and lysophatidic acids, are strong emulsifiers. If these compounds remain in the oil during the alkali refining/neutralization step, they may inhibit the separation of the soaps. Phospholipids (also called phosphotides) will react with water to form insoluble sediments.

Alkali refining or neutralization: Due to the length of time between harvesting the fish and sitting in holding tanks, the oil’s triglycerides break down through hydrolytic rancidity, into free fatty acids. This negatively impacts the quality of the oil, and causes it to begin to turn brown. To remove free fatty acids, pigments, phospholipids, and water-soluble materials, it’s necessary to alkali refine the oil. This process produces soaps that must be removed with water or steam washing, followed by centrifuging.

Water washing: Water washing and silica treatment remove the soaps created by the alkali, oxidation products and other trace metals.

Drying: Drying removes the moisture from the water washing. Moisture, heat, oxygen, light and reactive metals further degrade the oil.

Bleaching: The major objective of bleaching is to return the oil to an acceptable pale color using clays treated with mineral acids. Depending on how long the oil has been sitting, up to 2% bleaching earth may be used. Acid-activated bleaching earth also cleans out the hydroperoxides in the oil formed during previous steps.

Winterization: Winterization concentrates the omega fatty acids. This is addition by subtraction. The oil is cooled to sub-zero temperature, causing crystallization and reduction in the amount of saturated fatty acids. Triglycerides and waxes are also removed. Removing the saturated fats and triglycerides further destabilizes the oil, as the remaining polyunsaturated fats (in the form of omega-3 fatty acids) are very fragile and oxidize easily. The human body does not require concentrated levels of essential fatty acids, especially in an isolated form. Denaturing the oil creates an imbalance that severely weakens its effectiveness.

Deodorization: To remove additional free fatty acids, monoglycerides, diglycerides, hydroperoxides, aldehydes, ketones, chlorinated hydrocarbons, volatile compounds and pigments formed during the previous processing steps, deodorization is necessary. During this process, the oil can be heated up to 374℉ or higher as live steam passes through the oil at low pressure. This step may lead to the formation of trans fats (trans isomers) of EPA and DHA. A study on fish oil capsules on the European market found that all products studied had levels of trans fats. Trans fats were found in up to 4.5% of the total EPA and up to 5.9% of the DHA. This step also damages or destroys most of the vitamin A and vitamin D naturally found in cod liver oil.

Molecular distillation: Molecular distillation removes most of the remaining pesticides and organic pollutants, which include dioxins, lindane, DDT, as well as bromated compounds (flame retardants) and reduces all such environmental pollutants to lower levels. Temperatures can reach 395℉. Sometimes this step is used as a replacement for deodorization. Molecular distillation is also responsible for a tremendous loss of vitamins A and D naturally occurring in cod liver oil and the creation of trans fats due to high heat.

Synthetic vitamins: Almost all of the natural vitamin A (retinol) and vitamin D3 (cholecalciferol) is removed during the industrial processing of cod liver oil. At this stage, the majority of cod liver oil producers add vitamin A from a synthetic source, retinyl palmitate. Synthetic vitamin D3 derived from lanolin in sheep wool as a cholesterol source is purified to form 7-dehyrocholesterol, irradiated to form D3, and added to the highly processed cod liver oil. Sheep's wool is not a natural component of cod liver oil. Synthetics may also contain additives, colorings, fillers, byproducts, and other chemicals not found in the natural versions and are produced with the aid of harsh chemical reagents. Many animal studies have shown differences in the absorption of synthetic compared to natural vitamins. Synthetic vitamins do not perform the same functions in your body as vitamins found naturally in whole food, which are very complex and work with other nutrients to produce their specific biological effects. Many synthetic vitamins deplete the body of other nutrients, and the kidneys must work harder to excrete them through urine.

Antioxidants: Once the oil is cooled, antioxidants are always added to processed fish oil for human consumption to protect the oil from further oxidation. “Natural” forms of antioxidants, such as ascorbic acid, isolated vitamin E tocopherols from soy, citric acid from GMO corn, and spice extracts are often used. The most common synthetic antioxidants are BHA (butylated hydroxyanisole), BHT (butylated hydroxytoluene), TBHQ (tert-butylhydroquinone) and propyl gallate.

Flavorings: To make poor-quality tasting oils, most commercial cod liver oil producers will add flavorings such as “natural lemon flavor” to their products. While the flavor may be naturally derived from the lemon peel, the actual contents are proprietary, and the flavoring companies do not have to divulge their processes or ingredients (only certify that the flavoring is free of the eight major allergens). The flavorings are not organic, and some customers may have a reaction to the flavoring because of the citrus content. Other producers will use synthetic citrus flavorings and fruit flavorings derived from a mix of proprietary chemicals.

How Rosita® Extra Virgin Cod Liver Oil is created

Check out our resources on how Rosita® Extra Virgin Cod Liver Oil is naturally created without heat or mechanical processes to retain all of its naturally occurring nutrients as they are in the liver of a living codfish. 



  • O’Connor A. What’s in Your Fish Oil Supplements? New York Times. 12 Jan 2014
  • Bimbo, A. The Production and Processing of Marine Oils. The AOCS Lipid Library.
  • Hjaltason B. and Garaldsson GG. Fish Oils and Lipids from Marine Sources. In
  • Modifying Lipids for Use in Food. F.D. Gunstone, edit. CRC Press: Boca Raton FL 2006. 64.
  • Ibid, p 74
  • Rajakumar K. Vitamin D, cod-liver oil, sunlight, and rickets: a historical perspective. Pediatrics. 2003 Aug; 112(2):e132-5;  Hjaltason B. and Garaldsson G.G., 56
  • Editorial. Oilless Cod Liver Oil. JAMA 20 Feb 1915; 64(8) 667-8
  • Ottoboni A. Ottoboni F.  The Modern Nutritional Diseases. 2013. NV: Vincente Books; Hjaltason B. and Garaldsson G.G., 57.
  • Mercola J. Important Cod Liver Oil Update. 23 Dec 2008.;;  Cannell J. Newsletter: Vitamin A Toxicity. Vitamin D Council. 15 Dec 2008
  • Sciotto C. Mjos SA. Trans Isomers of EPA and DHA in Omega-3 Products on the European Market. Lipids. 47: 650-667/
  • Hjaltason B. and Garaldsson G.G. 68.
  • Ibid. 64-68.
  • Ibid. 68-70.
  • Ibid. 70
  • Ibid 68-69
  • Albert BB et al. Fish oil supplements in New Zealand are highly oxidized and do not meet label content of n-3 PUFA. Scientific Reports 5(7928).  21 Jan 2015
  • Fresh or rotten?  Rotten fish oil polluting the market and putting health at risk.
  • Rubin Report.   Lite oksiderte omega-3 oljer og potensielle helsefordeler. NOFIMA 196:4647  October 2010,