TG, EE and rTG – what’s the difference?
Several studies show that many health benefits increase with increasing dose (for example GOED quote a 9% reduction in myocardial infarctions (heart attack) with every 1g of EPA and DHA consumed [1]).The most commonly used fish oils for food supplements contain approximately 160mg/g EPA and 100mg/g DHA although these values can vary both with species and seasons. Increasing the concentration of EPA and DHA is of interest for supplement manufacturers and consumers alike because it allows consumption of less oil for any given amount of EPA/DHA, as well as standardized products.
Omega-3 in fish is present as a triglyceride, and this is also the most common chemical form for stored fats in the human body. Each triglyceride molecule has a glycerol backbone connected to 3 lipids. When fats are digested, they are broken down by pancreatic lipases which remove lipids from the glycerol backbone. These fragments are absorbed by the intestines and triglycerides are re-synthesized in intestinal cells before being distributed around the body.
Concentration of fatty acids by distillation requires the conversion of triglycerides to ethyl esters. This process maintains the structure of the fatty acid but changes the backbone binding the fatty acids together. Many manufacturers wish to provide concentrated omega-3 similar to its natural form, which is performed by reconstitution of the ethyl esters to a triglyceride. This form is called re-esterified triglyceride or rTG.
These rTGs have 3 fatty acids bound to the backbone exactly as for the natural triglyceride, but the 3 lipids will have a higher level of EPA and DHA. When this oil is eaten it will be broken down in the same manner as before by pancreatic lipases. Again, the fragments will be reconstituted by the intestinal cells into a triglyceride form.
Ethyl esters have been the chosen chemical form for pharmaceutical use. For supplements, many consumers prefer the rTG form due to their structural similarity to natural oils. There may also be a biological advantage to rTG since the uptake of lipids is higher in the rTG form compared to ethyl esters. A study comparing the EPA and DHA content in blood showed a statistically significant benefit of rTG vs ethyl esters after 2 weeks of supplementation [2].
Epax encourages the use of high purity oils for consumers. High purity ensures the removal of harmful components present in fish. For EPAX® oils, purity also means use of some of the highest standards for oxidation and additionally includes a guarantee for the efficient conversion of EE to rTG. EPAX® TGN oils are guaranteed to have a minimum of 90% rTG which is amongst the highest values on the market. A recent study demonstrates the importance of this focus on purity. EPA and DHA levels were measured in blood following consumption of an oil with >95% rTG vs an oil with <75% rTG. The total EPA and DHA concentration in blood after 16 weeks was statistically significantly higher with the >95% TG oil than the comparator despite similar dosage of EPA and DHA [3]. Interestingly, the industry standard for rTGs is as low as min. 50% TG content, and in some oils marketed as ‘rTG’ we have seen up to 25% EE content.
Therefore, purity in the form of a high concentration of EPA/DHA, low oxidation and high levels of rTG provide an excellent omega-3 oil for consumers.
References
- Bernasconi, A.A., et al., Omega-3 Benefits Remain Strong Post-STRENGTH. Mayo Clin Proc, 2021. 96(5): p. 1371-1372.
- Dyerberg, J., et al., Bioavailability of marine n-3 fatty acid formulations. Prostaglandins Leukot Essent Fatty Acids, 2010. 83(3): p. 137-41.
- Minton, S.T., et al., Comparative membrane incorporation of omega-3 fish oil triglyceride preparations differing by degree of re-esterification: A sixteen-week randomized intervention trial. PLoS One, 2023. 18(1): p. e0265462
