There has to be made a distinction beween several Omega 3 fatty acids, namely **[ALA](https://en.wikipedia.org/wiki/Alpha-Linolenic_acid)**, **[EPA](https://en.wikipedia.org/wiki/Eicosapentaenoic_acid)** and **[DHA](https://en.wikipedia.org/wiki/Docosahexaenoic_acid)**. 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](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3131561/#b19-marinedrugs-09-01056)* and other algae.
 - DHA is even rarer in plants. Only *[some special type of algae](https://en.wikipedia.org/wiki/Docosahexaenoic_acid#Discovery_of_algae-based_DHA)* 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](https://www.ncbi.nlm.nih.gov/pubmed/18589030) your diet with algae-based EPA and DHA.