Guide
Fish oil vs ethyl ester fish oil: does the form matter
"Regular" fish oil (natural triglyceride form) and ethyl ester fish oil are chemically different, and an older single-dose study found ethyl esters absorbed worse without food. A more recent, dose-matched trial found little difference between the two when dosed and taken properly.
"Regular" fish oil — the natural triglyceride form, where the fatty acids stay attached to their original glycerol backbone — and ethyl ester fish oil, where they're bonded to ethanol instead, are chemically different. An older study without food found the ethyl ester form absorbed much worse. Taking it with a fatty meal, and matching the dose properly, closes most of that gap.
What the difference actually is
Fish oil starts out in the triglyceride form naturally — that's how EPA and DHA sit in the fish. To concentrate a product to a higher percentage of omega-3s, some manufacturers convert the fat to an ethyl ester first, then may or may not convert it back. Ethyl ester fish oil is common in higher-concentration and some prescription products; the natural triglyceride form is common in standard softgels. This is a narrower comparison than the full set of forms fish oil comes in — see fish oil forms compared for triglyceride, ethyl ester, re-esterified triglyceride, free fatty acid and krill oil side by side.
What the research found
An older study gave 8 men a single dose of fish oil as either the natural triglyceride form or the ethyl ester form, without any food. The triglyceride form absorbed noticeably better; the ethyl ester form absorbed substantially worse — about a fifth as well. That result is the source of ethyl esters' reputation as the weaker-absorbing form.
A separate study measured what happens when either form is taken with a high-fat meal (44 grams of fat) instead of a low-fat one. Absorption of EPA from the triglyceride form improved from 69% to 90% with the higher-fat meal. Absorption of both EPA and DHA from the ethyl ester form roughly tripled with the higher-fat meal — a much bigger jump, meaning the ethyl ester form's absorption is far more dependent on how much fat is in the meal it's taken with.
A more recent, better-designed trial gave 66 healthy adults a matched 1.3 g/day dose of EPA and DHA as either fish oil ethyl ester, fish oil triglyceride, or krill oil, for four weeks. Blood EPA+DHA levels didn't differ significantly between the three forms — bioavailability varied by less than 24%. That trial was funded by a supplement ingredient manufacturer, which is worth knowing when weighing the result. Taken together, the biggest documented gap — ethyl ester without food — mostly disappears once the dose is matched and the meal has some fat in it.
Where our label sits
Electric Tiger Omega-3's panel lists the ingredient as "fish oil concentrate" — 1,000 mg per softgel, providing 180 mg EPA and 120 mg DHA — without stating which specific ester form it is. That's a real gap in what the label tells you, and a fair question to ask any fish oil brand, ours included, if the distinction matters to you. Our directions say to take it with meals, which is the more evidence-backed choice for either form.
Questions people ask
Is ethyl ester fish oil worse than regular fish oil?
Not once the dose is matched and it's taken with food, based on the trial above. Without food, an older single-dose study did find it absorbed substantially worse than the natural triglyceride form.
Should I avoid ethyl ester fish oil?
There's no trial showing a meaningful downside to the ethyl ester form specifically when taken as directed, with food. It's the form used in some higher-concentration and prescription-strength products for a practical reason — it's easier to concentrate to a high EPA+DHA percentage.
How do I know which form my fish oil is?
The supplement facts panel should state it, though not every brand does — ours currently lists "fish oil concentrate" without specifying. Contacting the brand directly is the way to get a definitive answer if the label doesn't say.
Sources
- Lawson LD, Hughes BG. Human absorption of fish oil fatty acids as triacylglycerols, free acids, or ethyl esters. PMID 3358766.
- Lawson LD, Hughes BG. Absorption of eicosapentaenoic acid and docosahexaenoic acid from fish oil triacylglycerols or fish oil ethyl esters co-ingested with a high-fat meal. PMID 2847723.
- Yurko-Mauro K, et al. Similar EPA and DHA plasma levels achieved with fish oil or krill oil in a randomized double-blind four-week bioavailability study. PMID 26328782.
- Electric Tiger Omega-3 Supplement Facts: product page.
Related reading: fish oil forms compared, how to choose a good fish oil, and how much fish oil should you take a day.
Sources
- Human absorption of fish oil fatty acids as triacylglycerols, free acids, or ethyl esters In a small single-dose trial without food, free fatty acid fish oil was absorbed best, the natural triglyceride form somewhat less well, and the ethyl ester form substantially worse — about a fifth as well as the free acid form.
- Absorption of eicosapentaenoic acid and docosahexaenoic acid from fish oil triacylglycerols or fish oil ethyl esters co-ingested with a high-fat meal A small 1988 trial found that eating fish oil with a high-fat meal raised EPA absorption from the natural triglyceride form from 69% to 90%, and roughly tripled absorption of both EPA and DHA from the more processed ethyl ester form, compared with a lower-fat meal.
- Similar eicosapentaenoic acid and docosahexaenoic acid plasma levels achieved with fish oil or krill oil in a randomized double-blind four-week bioavailability study When doses of EPA and DHA were matched exactly, a four-week trial in 66 healthy adults found no statistically significant difference in blood levels between ethyl ester fish oil, triglyceride fish oil, and krill oil; this trial was funded by a supplement ingredient manufacturer.
*These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease.
