, ,

Removing ‘Impurities’ – What’s REALLY in Fish Oil?

FISH OIL – Impurities or Nature’s Gift?

By Kirsa Sommersted

I found this article on fish oil intriguing as it highlights the challenge in buying quality supplements – reading the label is just not enough any more. We involve ourselves in checking out brands online, reading reviews to ensure we are getting exactly what we want! In addition to reading this article, you may be interested in our Best Foods for Me post

Manufacturers refine fish oils to remove “impurities”. Why do the manufacturers do this? According to Peckel Möller, founder of the Möller process, it is “an endeavor to overcome the difficulties in administering the oil”.1 In other words, it is a way to improve properties like taste, odor, and texture. But what are these “impurities”? Is it truly a good idea to remove them? What are we left with after refining the oil?


 Online articles describe a variety of processes that fish oil manufacturers use to refine fish oils and eliminate what they refer to as “impurities”. These refining processes include carbon filtration, earthen filtration, winterization, degumming, alkali refining, physical refining, sodium carbonate, bleaching, and deodorization.2 In fact, a quick Google search will retrieve over five million results for anyone interested in learning more about fish oil refining! The fish oil produced by these refining processes, even simple filtration, can strip the fish oil of vitamins and omega-3 fatty acids. These important nutrients are then put back into the oil in a synthetic, artificial form.


Are these truly impurities? The word “impurities” implies that fish oil contains contaminants or foreign bodies that do not belong in the oil.
Here is a list of “impurities” removed when fish oil is refined2:
  1. Triglycerides
  2. Free fatty acids
  3. Pigments
  4. Waxes
  5. Phospholipids
  6. Oxidation products
  7. Phosphatides
  8. Mucilaginous materials
What is fish oil and what does it contain?
Fish oil contains the following2:
  1. Triglycerides
  2. Free fatty acids
  3. Fatty acids
  4. Pigments
  5. Waxes
  6. Phospholipids
  7. Antioxidants
  8. Sterols
  9. Vitamins

If you compare the two lists, you might notice that they are almost identical! This means that none of these “impurities” are true impurities!


Since these “impurities” are actually all naturally occurring components of fish oil, I believe it is more appropriate to refer to them as innate particles.

Some of these innate particles have known benefits. In fact, if you are taking a fish oil supplement, there is a good chance that it is precisely because you want the vitamin D, vitamin A, and omega-3 fatty acids contained in the oil. Unfortunately, when fish oil is refined these innate particles are depleted, or completely removed, and have to be synthetically added back into the fish oil.

The synthetic vitamins and synthetic omega fatty acids that manufacturers use as replacements are difficult for the body to digest, and can lead to negative, and possibly toxic effects in the body.3-9


What about all the other innate particles that are not added back in using synthetic substitutes? Could any of them have beneficial effects?


If we look closer at these innate particles we find that almost all of them are lipids, or lipid derivatives. “Lipid” is a generic term used to describe substances that are not soluble in water. They store energy, serve as signaling molecules, and are an integral part of membranes.10


Triglycerides, also know as “fats”, are lipids that consist of a glycerol backbone and have three fatty acids attached. 10 When triglycerides under go lipolysis, they release the glycerol from the fatty acids, creating free fatty acids. Color pigments in fish oil are either natural, or the results of enzymatic browning (oxidation), non-enzymatic browning, and/or caramelization 2. One of the most important color pigments found in seafood is carotenoid.11,12 Carotenoid is an antioxidant and a precursor of vitamin A.

Researchers are investigating these other particles and are indeed discovering that some of them have beneficial properties.13-17 In fact; Yin and colleagues believe that some of the beneficial effects of fish oils could be due to novel oxidation products.11


Taken together, what does this all mean? Simply put, it means that of all the innate particles destroyed or damaged during the oil refining process, very few are actually synthetically put back into the fish oil. All the other unknown beneficial innate particles are gone.


Informed consumers know, however, that whole food products contain all of these undiscovered beneficial innate particles. Don’t wait for researchers to find these unknowns; enjoy what nature has already perfected!
  1. Möller, P. (1895). Cod-liver oil and Chemistry. London, Christiana, P Möller https://archive.org/details/codliveroilandc01mlgoog
  2. Irianto HE. (1992). Fish oil: refining, stability, and its use in canned fish for the Indonesian market [dissertation]. Palmerston North, NZ: Massey University.
  3. Group E. (2009). The differences between synthetic and natural vitamins. Global Healing Center. [Updated Feb 16,,2016; accessed May 11, 2017.] http://www.globalhealingcenter.com/natural-health/synthetic-vs-natural-vitamins/.
  4. Mazzaferro S, Goldsmith D, Larsson TE, Massy ZA, Cozzolino M. (2014). Vitamin D metabolites and/or analogs: which D for which patient? Curr Vasc Pharmacol 12(2):339-49.
  5. Clement B. (2006). Nutri-con: the truth about vitamins and supplements. Organic Consumers Association. [Accessed May 5, 2017]. https://www.organicconsumers.org/news/nutri-con-truth-about-vitamins-supplements.
  6. Saghir M, Werner J, Laposata M. (1997). Rapid in vivo hydrolysis of fatty acid ethyl esters, toxic nonoxidative ethanol metabolites. Am J Physiol 273:G184-90.
  7. Fave G, Coste TC, Armand M. (2004). Physicochemical properties of lipids: new strategies to manage fatty acid bioavailability. Cell Mol Biol 50(7):815-31.
  8. Yang LY, Kukis A, Myher JJ. (1990). Intestinal absorption of menhaden and rapeseed and their fatty acid methyl and ethyl esters in the rat. Biochem Cell Biol 68:480-91.
  9. Yang LY, Kuksis A, Myher JJ. (1990). Lipolysis of menhaden oil triacylglycerols and the corresponding fatty acid alkyl esters by pancreatic lipase in vitro: a reexamination. J Lipid Res 31(1):137-47.
  10. Christie WW. (2013). What do lipids do? Their biological functions. Lipid Library. [Accessed May 11, 2017] http://lipidlibrary.aocs.org/Primer/content.cfm?ItemNumber=39370
  11. Simpson BK (Ed.). (2012). Food biochemistry and food processing, 2nd edition. Ames, IA: John Wiley & Sons, Inc.
  12. Shahidi F, Brown JA. (1998). Carotenoid pigments in seafoods and aquaculture. Crit Rev Food Sci Nutr 38(1):1-67.
  13. Gao L, Yin H, Milne GL, Porter NA, Morrow JD. (2006). Formation of F-ring isoprostane-like compounds (F3-Isoprostanes) in vivo from eicosapentaenoic acid. J Biol Chem 281(20):14092-9.
  14. Yin H, Brooks JD, Gao L, Porter NA, Morrow JD. (2007). Identification of novel autoxidation products of the Ω-3 fatty acids eicosapentaenoic acid in vitro and in vivo. J Biol Chem 282(41):29890-901.
  15. Sethi S, Ziouzenkova O, Ni H, Wagner DD, Plutzky J, Mayadas TN. (2002). Oxidized omega-3 fatty acids in fish oil inhibit leukocyte-endothelial interactions through activation of PPARΑ. Blood 100:1340-6.
  16. Khaddaj-Mallat R, Morin C, Rousseau E. (2016). Novel n-3 PUFA monoacylglycerides of pharmacological and medicinal interest: anti-inflammatory and anti-proliferative effects. Eur J Pharmacol 792:70-2. doi: 10.1016/j.ejphar.2016.10.038
  17. Alvarez-Curto E, Milligan G. (2016). Metabolism meets immunity: the role of free fatty acids receptors in the immune system. Bio Chem Pharm 114:3-13.