{
  "dataset": "omega-3-forms-comparison",
  "title": "Omega-3 (Fish Oil) Forms Compared — bioavailability, source, and best use",
  "sourcePage": "https://verifiedsupplementdata.com/omega-3/forms-compared/",
  "license": "CC BY 4.0",
  "licenseUrl": "https://creativecommons.org/licenses/by/4.0/",
  "attribution": "Verified Supplement Data (2026), Omega-3 Forms Comparison",
  "dateModified": "2026-09-29",
  "methodology": "Absorption figures are from Dyerberg 2010 (PMID 20638827): rise in fasting-blood EPA+DHA over two weeks, relative to natural fish oil (=100%): re-esterified triglyceride 124%, free fatty acid 91%, ethyl ester 73%. Over six months the gap was smaller (PMID 21063431), and a fatty meal about triples ethyl ester absorption (PMID 2847723). Krill is not proven better when doses are matched (PMID 26328782, 36960737, 24952576). Algal DHA matched cooked salmon (PMID 18589030). The label figure that matters most is EPA+DHA per serving, not the fish oil total.",
  "forms": [
    {
      "name": "Re-esterified triglyceride",
      "aka": "rTG",
      "absorption": "124% of natural fish oil in a two-week study (PMID 20638827)",
      "source": "Concentrated fish oil, turned back into triglyceride",
      "bestFor": "Absorbed best in a two-week study; matters most with a low-fat meal",
      "notes": "Fish oil is concentrated as ethyl ester, then turned back into the triglyceride form found in fish. It raised blood EPA and DHA 1.7 times as much as ethyl ester over two weeks (PMID 20638827). Over six months the gap was smaller: omega-3 index up 197% against 171% for ethyl ester at the same dose (PMID 21063431)."
    },
    {
      "name": "Natural triglyceride",
      "aka": "TG",
      "absorption": "100% (the reference) in the same study",
      "source": "Fish oil, lightly processed or concentrated",
      "bestFor": "Everyday use",
      "notes": "The form omega-3s take in fish. It raised blood EPA and DHA about 1.4 times as much as ethyl ester in the two-week study (PMID 20638827). Read the label for EPA+DHA per softgel: some TG oils are concentrated and some are not."
    },
    {
      "name": "Ethyl ester",
      "aka": "EE",
      "absorption": "73% of natural fish oil in the same study",
      "source": "Concentrated fish oil, not turned back",
      "bestFor": "Fine value if you take it with a meal",
      "notes": "The form fish oil takes when it is concentrated. It absorbs poorly with a low-fat meal; with a meal that had 44 g of fat, its absorption rose about three-fold, to about 60% (PMID 2847723). Both forms raised the omega-3 index strongly over six months (PMID 21063431)."
    },
    {
      "name": "Free fatty acid",
      "aka": "FFA",
      "absorption": "91% of natural fish oil in the same study",
      "source": "Fish oil split into free fatty acids",
      "bestFor": "Some prescription products",
      "notes": "Not different from natural fish oil in the two-week study (PMID 20638827). Rare on store shelves."
    },
    {
      "name": "Phospholipid",
      "aka": "Krill oil",
      "absorption": "Not proven better than fish oil when doses are matched",
      "source": "Antarctic krill",
      "bestFor": "Few people: it holds little EPA+DHA per capsule",
      "notes": "Some small studies found krill raised blood omega-3 more; others found no difference at matched doses (PMID 26328782, 36960737). In one 28-day study at each label’s dose, a concentrated rTG oil raised blood omega-3 most, then ethyl ester, salmon oil and krill. Dose and form changed together, and the authors said both may matter (PMID 24952576). Nordic Naturals, an rTG maker, paid for it, and Nutrasource, the company that also runs IFOS, ran it. That does not make the result wrong, but it is not an independent test. A krill capsule holds much less EPA and DHA than a fish oil concentrate, so you need several."
    },
    {
      "name": "Algal oil",
      "aka": "Algae",
      "absorption": "About matched cooked salmon for DHA in one small 2-week study (PMID 18589030)",
      "source": "Marine algae (vegan)",
      "bestFor": "People who eat no fish",
      "notes": "Made from the algae fish get their omega-3 from, usually in triglyceride form and often richer in DHA than EPA. In a two-week study of 32 adults, algal DHA capsules raised blood DHA as much as the same DHA from cooked salmon (PMID 18589030). It costs more per gram than fish oil."
    },
    {
      "name": "Cod liver oil",
      "aka": "Cod liver",
      "absorption": "Natural triglyceride",
      "source": "Cod livers",
      "bestFor": "Only if you want its vitamin A and D too",
      "notes": "It adds vitamin A and vitamin D. The adult upper limit for preformed vitamin A is 3,000 mcg a day, including in pregnancy, and too much can cause birth defects, so do not stack it with other vitamin A (NIH ODS). Read the vitamin A line on the label."
    }
  ],
  "citations": [
    "PMID:20638827",
    "PMID:21063431",
    "PMID:2847723",
    "PMID:26328782",
    "PMID:36960737",
    "PMID:24952576",
    "PMID:18589030"
  ]
}