A: Omega-3 in fish oil can exist in any of these 3 forms: unconcentrated natural triglyceride (TG), concentrated ethyl ester (EE) and concentrated re-esterified triglyceride (rTG) forms. rTG concentrate provides up to 90% of omega-3 and EE concentrate typically contains 50 to 70% omega-3. With this higher concentration, it effectively delivers higher dosage of omega-3 into body cells with a smaller volume of fish oil.

As rTG omega-3 is identical to natural triglyceride form, it can be tolerated, absorbed and utilised more easily by human body with virtually no gastrointestinal side effect, as compared to omega-3 in EE form. A recent study has shown that bioavailability of omega-3 in rTG form is 70% higher than ethyl esters form and 24% more superior than the natural triglyceride form in unprocessed fish oil. Omega-3 in rTG form is also more stable and oxidises less easily than EE form. Fish oil contains DHA in EE form was found to decay 33% more rapidly than omega-3 fish oil in triglyceride form. Although rTG form is better than EE form, majority of concentrated omega-3 fish oils are offered in the EE form as it is more costly to re-esterify ethyl ester fish oil back to rTG form.