Fish oil: triglyceride (TG) vs ethyl ester (EE)
Short answer: NIH ODS says omega-3s as re-esterified triglycerides (rTG), natural triglycerides (TG) and free fatty acids have somewhat higher bioavailability than ethyl esters (EE), but all forms significantly raise plasma EPA and DHA.
| Form | What ODS says | Notes |
|---|---|---|
| Natural triglyceride (TG) | The form that occurs naturally in fish oil; somewhat more bioavailable than EE. | |
| Ethyl ester (EE) | Made by replacing the glycerol of the triglyceride with ethanol; somewhat less bioavailable, but still raises plasma EPA and DHA significantly. | |
| Re-esterified triglyceride (rTG) | Ethyl esters converted back to triglycerides; somewhat more bioavailable than EE. | |
| Phospholipids (krill oil) | Some studies show somewhat higher bioavailability than fish oil; others do not. |
Compare the milligrams of EPA + DHA on the label first, then the form. ODS notes a typical 1,000 mg fish oil capsule has about 180 mg EPA and 120 mg DHA, but products vary widely.
Safety: EFSA says long-term EPA + DHA supplements up to about 5 g a day combined appear safe; FDA says supplements giving no more than 5 g a day are safe when used as recommended. People on warfarin or similar anticoagulants should ask their doctor first.
Sources
This page only paraphrases the sources above and is not medical advice. If you are pregnant, breastfeeding, take medicines or have a chronic condition, ask a doctor or pharmacist first.