Comparative guide
Fish oil vs flaxseed oil
Flaxseed oil is an omega-3. It is alpha-linolenic acid, the short one. Fish oil is EPA and DHA, the long ones. The body converts a little of the first into the second. The reviews say that conversion does not stand in for eating the long ones.
- Brenna 2009 (PMID 19269799): supplemental ALA raises EPA and DPA in blood. ALA or EPA supplements have little effect on DHA. Preformed DHA raises DHA.
- Burdge 2005 (PMID 16188209): conversion of ALA to EPA is limited, and conversion on to DHA is very low. A larger fraction is converted in women than in men. ALA is still a limited source of the long-chain fats.
- Lane 2022 (PMID 33576691): a scoping review of trials from 2010 to 2020. High-dose flaxseed or echium oil did not raise the omega-3 index, and some studies showed reductions. Microalgal oil raised it.
- Takic 2022 (PMID 35889342): in the obesity papers they reviewed, ALA raised EPA and did not raise DHA or the omega-3 index.
If the goal is EPA and DHA in blood, take EPA and DHA. Flaxseed oil is a different fat with its own uses as food. It is the weaker way to move the omega-3 index.