Essential fatty acids (EFAs) are those that the human body needs to function (not meaning energy) but cannot synthesize them from other sources. Therefore, they must be consumed as a part of diet. These are the shortest (18-carbon) ω-3 and ω-6 chains, which have a double bond between the 9th and 10th carbon (counted from the start, not from the ω end).
Essential fatty acids (also SC-PUFA, short chain PUFAs – shortest though having 18 carbons) are:
- alpha-linolenic acid (ALA): ω-3 fatty acid (best sources: ground / crushed flaxseed, flaxseed oil, chia seeds)
- linoleic acid (LA): ω-6 fatty acid (sources: various nuts, seeds including flax, and their oils – but avoid too high intake, see also ω-3:ω-6 ratio
The name of both acids is derived from the name of flax (lat. linon).
From these EFAs, the organism can already create (by chain extension and desaturation) another ω-3 and ω-6 fatty acids, important for the body (also called LC-PUFA, long chain PUFA – 20 or 22 carbons):
- eicosapentaenoic acid (EPA): ω-3 (synthesized from ALA / LA, but with only a few% efficiency, so it is advisable to consume in food: fatty sea fish, seafood, and some marine micro-algae – primary source of EPA / DHA in marine animals)
- arachidonic acid (AA, from lat. arachis ie peanut, although not found there): ω-6 (synthesized from LA via GLA, with even lower efficiency than EPA, so it is advisable to consume as a part of diet: meat, animal fat, eggs, fish, algae)
- docosahexaenoic acid (DHA): ω-3 (synthesized from EPA / AA, also with minimal efficiency, better to consume in food – same sources as EPA)
In the case of unhealthy diet, the synthesis of these LC-PUFAs is also impaired, and their deficit is even more pronounced. These three LC-PUFAs are therefore also sometimes, in the broader sense, classified as essential or “conditionally” essential FA.