Omega-3 fish oil comes in two types, natural triglycerides and ethyl esters. However, there’s a big difference between the two, and choosing whether to take a natural triglyceride or an ethyl ester supplement is the most important thing to consider when choosing the right omega-3 fatty acids. This is because the type affects how much omega-3 can actually be absorbed in the stomach. Also, it matters how effective that omega-3 is when it’s actually in the body.
What Are Omega-3 Triglycerides and Ethyl Esters?
Triglycerides (TG) are how fats are normally stored in the body, and they make up about 95% of fats in the diet. Therefore, they’re the natural form of omega-3 in fish (1).
Omega-3 TGs are called Triglycerides because they contain 3 fatty acids attached to a glycerol backbone. Two main Omega-3 fatty acids found in Omega-3 supplements are eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA).
Omega-3 Ethyl Esters (EE’s) are artificially created in a lab by breaking the bond between the fatty acids and their glycerol backbone. Then a single fatty acid is attached to a molecule of ethanol (alcohol) in a process known as trans-esterification. The reason companies make fish oil Ethyl Esters is because it’s necessary to concentrate the fish oil and to remove impurities.
Companies can only create high-strength EPA and DHA omega-3 supplements free from contaminants by using this process. Without concentrating the fish oil, it’s extremely difficult to get a proper dose of omega-3. For example, a supplement like cod liver oil that hasn’t been concentrated has a very low level of EPA and DHA. Cod liver oil and other fish oils also often cause GI upset as well as other side effects due to their impurities, especially when taken in large enough doses to provide a full serving of EPA and DHA (3).
Ethyl Ester Fish Oil
EE fish oil is still technically fish oil concentrate rather than real fish oil. Although it can legally be called fish oil, it’s really ‘semi-synthetic’ because although ethanol and fatty acids are both natural substances, they are never actually found together in nature.
While the trans-esterification process is necessary to make concentrated and pure fish oil, the EE concentrate can actually be converted back to the natural triglyceride form as re-esterified fish oil. Specialist enzymes are used to altogether remove the ethanol backbone thus creating separate free fatty acids and ethanol.
The ethanol is removed, and glycerol is then reintroduced, and the enzymes reattach 3 fatty acids to the glycerol backbone creating natural omega-3 triglycerides again. These re-esterified omega-3’s are still completely pure and with a much higher EPA and DHA concentrations, but they are now back in their natural form.
However, this last step is skipped by the vast majority of fish oil manufacturers because it’s expensive, adding around 40% to the raw material costs as well as being time-consuming. Because of this, the vast majority of omega-3 fish oils on the market today are in the artificial EE formulation and not TG fish oil.
Why Is It So Important To Buy Triglyceride Fish Oil?
The first reason is that because triglyceride fish oil is in its natural form, it has a much higher bioavailability than omega-3 ethyl esters (3, 7-11). That means more of the EPA and DHA in triglyceride fish oil can be absorbed and utilized by the body than it can from EE fish oil (2).
The second reason is that the unnatural chemical formulation of EE’s means they must be broken down differently by pancreatic lipase enzymes, after being emulsified by bile acids in the small intestine. The enzymes must remove the ethanol bond from the fatty acid in the EE form of oil, and then attach it to other dietary glycerol to form a triglyceride before it can be properly absorbed.
This Is Why You Should Always Choose Triglyceride Instead of EE Fish Oil
The absorption happens in the cells lining the intestinal wall known as enterocytes. Only once this process is completed can the omega-3 fatty acids be transported through the lymph system on chylomicrons and eventually enter the bloodstream at the thoracic duct. The process is much more inefficient, less effective, and slower with EE fish oil than TG fish oil (8, 10).
One particular study went on to show that the pancreatic lipase enzymes hydrolyze the ethanol bonds in EE fish oil between 10 and 50 times less efficiently than they hydrolyze the glycerol bonds in triglycerides (12).
The second reason is that EE fish oil oxidizes more quickly and easily than triglyceride fish oil. Oxidation is when a molecule breaks down chemically and becomes rancid. Polyunsaturated fatty acids are particularly prone to oxidation because of their double bond structures. This is why fish oils always contain antioxidants to prevent this oxidation from happening (most commonly vitamin E tocopherols). Several studies have shown EE fish oil to oxidize faster than fish oil triglycerides at all temperatures when measured through peroxide and anisidine values (13-16).
How Much Better Are Omega-3 Triglycerides Than Ethyl Esters?
One study showed that omega-3 in the triglyceride form has 71% greater absorption than EE’s (3). Another study found that free fatty acids were 400% better absorbed than ethyl esters (6). The ethyl ester omega-3 supplement used in the study was actually Lovaza, which is produced by GSK and is only available on prescription. This unfortunately means that doctors are still currently prescribing the inferior EE omega-3 form of fish oils.
The scientific and medical community has still not fully understood that different types of fish oil produce different effects and results. Omega-3 is one of the most researched substances in medical history, but much of the research so far has only tested the benefits of EE fish oil.
However, more research is starting to be published, looking at the different effects of EE and triglyceride fish oil once they have been absorbed into the body.
For example, one six-month study showed that triglyceride supplements had better bio-availability than EE supplements (4), and also that triglyceride omega-3 was significantly better at reducing circulating blood triglyceride levels than EE fish oil (5). Circulating triglyceride levels in the blood are a significant CV risk marker, and one of the criteria used to diagnose metabolic syndrome.
How Do I Know If My Omega-3 Supplement Is Triglyceride or Ethyl Ester?
Check your bottle of omega-3. If it doesn’t specifically say whether it’s ethyl ester or triglyceride, then it’s an ethyl ester. That’s because it’s so much more expensive to produce triglyceride fish oil. So, every company that does so clearly advertises the fact on their bottles.
If you are still unsure, contact the company who makes your omega-3 and ask to see their 3rd party testing certificates, which will indicate whether it’s EE or TG. There’s also a test you can perform at home. However, it does involve using up 20ml or so of fish oil.
However, if you still want to give it a go, put that 20 ml of fish oil in a polystyrene cup (20 ml is about 20 large capsules worth) and leave it for 10 minutes. After 10 minutes, if it’s an EE fish oil, it will have leaked through the cup. However, if it’s a triglyceride fish oil, it won’t leak (although the triglyceride fish oil may start to leak after 2-3 hours).
Intelligent Labs and Pure Omega-3
At Intelligent Labs, we will only ever sell the highest quality Triglyceride fish oil. We joined the GOED (Global Organization for EPA and DHA Omega-3s). As a GOED member, all our fish oil must meet the strict quality standards of the GOED Voluntary Monograph. Their mission is to ensure that Omega-3 supplements are safe, pure, and of the highest quality. All the companies that participated in developing the Monograph implemented strict quality standards. Read more about our partnership with GOED and our triglyceride fish oil Omega-3 fatty acids supplement.
 H Carlier, A Bernard, C Caselli. Digestion and absorption of polyunsaturated fatty acids. Reproduction Nutrition Development, EDP Sciences, 1991, 31 (5), pp.475-500
 Schuchardt, J., & Hahn, A. (2013). Bioavailability of long-chain omega-3 fatty acids. Prostaglandins, Leukotrienes, and Essential Fatty Acids (PLEFA), 89(1), 1-8.
 Dyerberg, J., Madsen, P., Møller, J., Aardestrup, I., & Schmidt, E. (2010). Bioavailability of marine n-3 fatty acid formulations. Prostaglandins, Leukotrienes and Essential Fatty Acids (PLEFA), 83(3), 137-141.
 J Neubronner, J.P. Schchardt, G Kressel, M. Merkel, C von Schacky, Ahahn. Enhanced increase of omega-3 index in response to long term n-3 fatty acid supplementation from triacyglycerides versus ethyl esters, Eur J. Clin Nutr. 65 (2011) 247 -254.
 J.P. Schuchardt, J. Neubronner, G Kressel, M Merkel, C von Schacky, A Hahn. Moderate doses of EPA and DHA from re-esterified triacyglycerols but not from ethyl-ester lower fasting serum triacyglycerols in statin-treated dyslipidemic subjects: results from a 6 month randomised controlled trial.
 Davidson MH, Johnson J, Rooney MW, Kyle ML, Kling DF. A novel omega-3 free fatty cid formulation has dramatically improved bioavailability during a low fat diet compared with omega-3-acid ethyl ester: The ECLIPSE (Epanova compared to Lovaza in a pharmacokinetic single dose evaluation) study. J coin Lipidol 2012;6:573-84.
 El Boustani S, Colette C, Monnier L, Descomps B, Crastes de Paulet A, Mendy F. Enteral absorption in man of eicosapentaenoic acid in different chemical forms. Lipids 1987; 22:711-4.
 Lawson LD, Hughes BG. Absorption of eicosapentaenoic acid and docosahexaenoic acid from fish oil triacyglyceriols or fish oil ethyl esters co investigated with a high fat meal. Biochem Biopsy REs Commun 1998: 156:960-3
 Lawson LD, Hughes BG. Human absorption of fish oil fatty acids as triacyglycerols, free acids, or ethyl esters. Biochem Biopsy REs Commun 1998: 152: 328-35.
 BeckermannB, Beneke M, Seitz l. Comparative bioavailability of eicosapentaenoic acid and docasahexaenoic acid from triglycerides, free fatty acids and ethyl esters in volunteers. Arneimmittelforschung 1990;40:700-4.
 Schuchardt JP, Schneider I, Meyer H, Neubronner J, von Schacky C, Hahn A. Incorporation of EPA and DHA into plasma phospholipids in respnse to different omega-3 fatty acid formulations- a comparative bioavailability study of fish oil vs krill oil. Lipids Health Dis 2011;10:145
. Yang, L.Y., A. Kuksis, and J.J. Myher, Lipolysis of menhaden oil triacylglycerols and the corresponding fatty acid alkyl esters by pancreatic lipase in vitro: a reexamination. J Lipid Res, 1990. 31(1): p. 137-47.
 Lee, H., et al., Analysis of headspace volatile and oxidized volatile compounds in DHA-enriched fish oil on accelerated oxidative storage. J Food Sci, 2003. 68(7): p. 2169-77.
 Yoshii, H., et al., Autoxidation kinetic analysis of docosahexaenoic acid ethyl ester and docosahexaenoic triglyceride with oxygen sensor. Biosci Biotechnol Biochem, 2002. 66(4): p. 749-53.
 Litiwinienko, G., Daniluk, A., & Kasprzycka-Guttman, T. , Study on autoxidation kinetics of fats by differential scanning calorimetry. 1. Saturated C12-C18 fatty acids and their esters. . Ind Eng Chem Res 2000. 39(1): p. 7-12.
 Sullivan Ritter, J.C., S.M. Budge, and F. Jovica, Oxidation rates of triglyceride and ethyl ester fish oils. Submitted to Food Chem (in review), 2014.