What Is a Triglyceride (in Omega-3 Supplements)?
A triglyceride is the most common form of dietary fat: three fatty acid chains attached to a glycerol backbone. When you eat fat, whether from olive oil, butter, or fish, most of it arrives in your body as triglycerides. In the omega-3 supplement world, the triglyceride form matters because it determines how your body absorbs the EPA and DHA in the product.
Fish oil in its natural state contains EPA and DHA bound to triglycerides. When fish oil is concentrated to increase the omega-3 content per capsule, the fatty acids are often converted to ethyl esters, a different chemical form. Some premium products then re-convert back to triglycerides (called "re-esterified triglycerides" or rTG). We explained what to check on your label in our omega-3 label guide.
Some research suggests the triglyceride form is absorbed modestly better than the ethyl ester form. Both deliver EPA and DHA effectively — the gap is real but not wide enough to make ethyl ester products useless.
That said: if your label says "triglyceride form" or "rTG," that is a genuine quality signal worth noticing. If the label says nothing at all about the form, the product is almost certainly ethyl ester. Silence on this point is not accidental; it is the cheaper processing method.
Our whole-cell phytoplankton products are not oil extracts, so the triglyceride vs ethyl ester distinction does not apply to them directly. When we characterised the lipid profile of our Nannochloropsis gaditana, we found that the EPA exists primarily as polar lipids (not as free triglyceride chains), which is what you would expect from a whole-cell microalgae format.
The absorption context is different from extracted fish oil, and direct comparisons between the two formats on the basis of triglyceride percentage are not meaningful. We cover the EPA vs DHA comparison and sourcing options in separate articles.
Triglycerides in Omega-3 Supplements at a Glance
- What they are: Three fatty acid chains attached to a glycerol backbone; the form in which most dietary fat (including natural fish oil) is found
- Natural cap: Unprocessed fish oil maxes out at roughly 30 per cent combined EPA and DHA as triglycerides; reaching 50 to 70 per cent requires conversion to ethyl esters during molecular distillation
- rTG reality: Re-esterified triglyceride products are premium, but published analyses show they often contain only 55 to 60 per cent actual triglycerides, with diglycerides and monoglycerides making up the rest
- Absorption: Triglyceride form absorbs modestly better than ethyl esters in published crossover trials; both deliver EPA and DHA, but the gap matters if you are trying to hit specific intake thresholds
- On labels: "TG" or "rTG" = triglyceride form; no form stated = almost certainly ethyl ester, which is cheaper to produce
- Whole-cell phytoplankton: The TG vs EE distinction does not apply; EPA in Nannochloropsis exists as polar lipids within the cell, not as free triglyceride chains
What our research found
When we reviewed the fish oil concentration process and analysed published lipid profiles for rTG products, two findings changed how we explain omega-3 form to customers.
Manufacturers use ethyl esters because concentration requires it. Natural fish oil maxes out at roughly 30 per cent combined EPA and DHA. To reach the 50 to 70 per cent concentrations you see on premium labels, the fatty acids must be converted to ethyl esters for molecular distillation. Re-esterifying back to triglyceride form adds a processing step and cost, which is why rTG products cost more.
Products labelled rTG are not always 100 per cent triglyceride. Published analyses show some re-esterified products contain 55 to 60 per cent triglycerides, 38 to 42 per cent diglycerides, and 1 to 3 per cent monoglycerides. The label says rTG. The lipid profile is a mixture.
That is not fraud; the re-esterification process is real and the product absorbs better than ethyl ester. But if you are paying a significant price premium on the assumption that rTG means pure triglyceride, the chemistry does not fully support that assumption.
Sources
- West AL et al. Pharmacokinetics of Supplemental Omega-3 Fatty Acids Esterified in Monoglycerides, Ethyl Esters, or Triglycerides in Adults in a Randomized Crossover Trial. Journal of Nutrition. 2021;151(5):1111–1118. PubMed
- Laidlaw M et al. Comparative membrane incorporation of omega-3 fish oil triglyceride preparations differing by degree of re-esterification. Prostaglandins, Leukotrienes and Essential Fatty Acids. 2023;190:102539. PubMed
Cara Hayes, MSc Nutrition and Dietetics (University of Sydney), writes all content in the Phytality Knowledge Centre. Read our editorial policy.
This article is for informational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Consult your healthcare provider before starting any supplement.
Methodology and Disclosure
Phytality manufactures whole-cell phytoplankton (not oil extract) and algae-derived DHA oil supplements. We have a commercial interest in omega-3 form being understood. Triglyceride biochemistry reflects standard lipid science. Absorption comparisons reflect published bioavailability research. No EFSA-authorised health claims are cited for omega-3 chemical form.
Last reviewed: March 2026
