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What is EPA (Eicosapentaenoic Acid)?
What is the chemical structure of EPA?
What are the physiological Roles of EPA?
Can you get EPA from a plant-based diet?
What are the sustainability considerations around EPA sources?
EPA (eicosapentaenoic acid) is a long-chain omega-3 fatty acid with 20 carbon atoms and 5 double bonds, classified as 20:5 n-3. It is found primarily in fatty fish and microalgae, and can be synthesised in limited amounts from dietary ALA in the liver. EPA is the primary omega-3 involved in the production of anti-inflammatory lipid mediators called eicosanoids and specialised pro-resolving mediators (SPMs).
Complete guide to omega-3 fatty acids
What is the chemical structure of EPA?
EPA belongs to the family of long-chain polyunsaturated fatty acids (LC-PUFAs).
Its structure includes:
- 20 carbon atoms
- 5 double bonds
- The first double bond at the third carbon from the methyl end
It is therefore classified as 20:5 n-3.
Its longer carbon chain and additional double bonds distinguish it structurally from ALA (18:3 n-3).
Where Does EPA Come From?
EPA comes primarily from fatty fish (salmon, mackerel, sardines, herring), marine oils, and microalgae — the original producers of EPA in the marine food chain. It can also be synthesised in the liver from dietary ALA, but conversion rates are low and variable, typically between 8% and 20%.
What are the physiological Roles of EPA?
EPA fulfils three primary physiological roles: it is the principal precursor to anti-inflammatory eicosanoids and specialised pro-resolving mediators (resolvins, protectins) that actively resolve inflammation; it competes with arachidonic acid (omega-6) for incorporation into cell membrane phospholipids, reducing pro-inflammatory signalling; and it contributes to triglyceride reduction and cardiovascular lipid homeostasis. The REDUCE-IT clinical trial demonstrated that high-dose EPA reduced major cardiovascular events by 25% in high-risk patients.
How does EPA differ from DHA?
EPA and DHA are both long-chain omega-3 fatty acids but serve distinct biological functions. EPA (20:5 n-3) is primarily involved in inflammatory signalling and eicosanoid production. DHA (22:6 n-3) is the dominant structural omega-3 in brain neuronal tissue and the retina, where it influences membrane fluidity and signal transduction. Both originate from ALA metabolism or direct marine intake.
Although both are long-chain omega-3 fatty acids, EPA and DHA differ structurally:
- EPA contains 20 carbons
- DHA contains 22 carbons
DHA is often described as more structurally significant in neural and retinal membranes, whereas EPA is more associated with signaling pathways.
Both originate from ALA metabolism or marine sources.
Can you get EPA from a plant-based diet?
EPA is not present in significant amounts in plant foods. On a plant-based diet, EPA must be synthesised from dietary ALA — a conversion that occurs in the liver at rates of 8–20%. Plant sources rich in ALA — including flaxseed, chia, walnuts, and sacha inchi oil — support this pathway, but direct EPA intake from algal oil supplements is the most reliable plant-based source.
What are the sustainability considerations around EPA sources?
EPA from marine sources depends on fisheries or algae cultivation.
As marine ecosystems experience increasing environmental pressure, plant-based omega-3 nutrition based on ALA represents a complementary model that does not rely directly on ocean biomass.
Written by the Dafee Science Team — published 20/03/2026. Dafeepédia content is developed from European regulatory sources (EFSA, EC Regulation 432/2012) and peer-reviewed scientific literature, and reviewed for accuracy before publication.
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