There has to be made a distinction beween several Omega 3 fatty acids, namely ALA, EPA and DHA. All three of them are needed in a healthy human, and humans can metabolise ALA into EPA, and EPA into DHA, although the process is inefficient, can be inhibited by high Omega 6 fat intake, and requires a huge supply of ALA (or EPA, to produce DHA). (Other Omega 3 acids exist, but are not as important for the human diet.)
- ALA occurs mainly in linseed, rapeseed, soy, walnuts and some other nuts, grains and pulses. It is easy to maintain a sufficient level of ALA in a vegan diet, as soon as the awareness is raised.
- EPA is rarely found in plants. The only food that supplies it naturally seems to be seaweed and other algae.
- DHA is even rarer in plants. Only some special type of algae supply it. It is very important for the brain and the nervous system.
In summary, in order to have a healthy supply of all Omega 3 fatty acids as a vegan, you need to do at least one of the following:
- Eat big amounts of linseed, rapeseed and soy. (Hopefully, you will metabolise sufficient EPA and DHA.)
- Eat EPA-rich seaweed, being cautious not to overdose with iodine and heavy metals. (Hopefully, you will metabolise sufficient DHA.)
- Supplement your diet with algae-based EPA and DHA.