ALA (alpha-linolenic acid) is an essential omega-3 fatty acid. ALA is a shorter-chain omega-3 fatty acid which the body can use to convert (albeit inefficiently) to longer-chain forms such as EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid).
EPA and DHA are long-chain omegas-3 fatty acids which are important for brain structure and function. Higher levels in the blood are associated with better brain and heart health.
EPA and DHA are not present in unfortified animal-free foods. Many vegans rely on the conversion of ALA (found in e.g., flax, chia, walnuts) to EPA and DHA. However, vegans seem to have lower levels in the blood in comparison to non-vegans and this may indicate lower levels overall. Hence, the requirement for taking pre-formed EPA/DHA is a hotly debated topic.
Evidence for taking preformed EPA/DHA is not very strong, but some lines of research suggest that taking supplements may be neuroprotective and cardioprotective.
Adult vegans should consider taking a low dose of EPA+DHA of 250-350mg a day. Pre-pregnant, pregnant and lactating women ought to supplement.
You can find my reasoning for these recommendations in this article.
The FAO suggests* following intakes for children1 :
|Dose of EPA+DHA
|0.1-0.18%E** (DHA only)
|10-12 mg/kg (DHA only)
|200-250mg (the adult dose commences at age of 10)
* Adequate Intake
** % of total energy intake
*** the estimation is based on provision of breast milk to meet half of the daily energy needs, the rest of the energy would come from non breast milk diet