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What is DHA (docosahexaenoic acid)?
What is the chemical structure of DHA?
What are the physiological roles of DHA?
Can you get DHA from a plant-based diet?
What are the sustainability considerations around DHA sources?
DHA (docosahexaenoic acid) is a long-chain omega-3 fatty acid with 22 carbon atoms and 6 double bonds, classified as 22:6 n-3. It is the most structurally complex omega-3 and the dominant fatty acid in brain neuronal tissue — comprising approximately 40% of total fatty acids in grey matter — and in the retina. DHA is found primarily in fatty fish, marine oils, and microalgae.
Complete guide to omega-3 fatty acids
What is the chemical structure of DHA?
DHA belongs to the long-chain polyunsaturated fatty acids (LC-PUFAs).
Its structure contains:
- 22 carbon atoms
- 6 double bonds
- The first double bond at the third carbon from the methyl end
It is classified as 22:6 n-3.
Compared to EPA (20:5 n-3) and ALA (18:3 n-3), DHA has:
- A longer carbon chain
- A higher degree of unsaturation
These structural differences influence its behavior within cell membranes.
Where Does DHA Come From?
DHA comes primarily from fatty fish (salmon, sardines, mackerel), marine oils, and algae-derived supplements — microalgae being the original producers of DHA in the marine food chain. In plant-based diets, DHA must be synthesised from ALA through a multi-step conversion process in the liver, but conversion rates to DHA are very low — typically below 1–4%.
What are the physiological roles of DHA?
DHA fulfils three primary physiological roles: it is incorporated into cell membrane phospholipids where its six double bonds increase membrane fluidity and modulate lipid raft dynamics; it is the dominant structural fatty acid in brain grey matter and retinal photoreceptor cells, where it influences receptor sensitivity and signal transduction; and it is the precursor to D-series resolvins, protectins, and maresins — pro-resolving mediators involved in tissue repair and the active resolution of inflammation.
Can you get DHA from a plant-based diet?
DHA is not present in plant foods. On a plant-based diet, DHA must be synthesised from dietary ALA — a conversion that is highly inefficient, with less than 1–4% of ALA converted to DHA in most adults. Algae-derived DHA supplements are the only reliable plant-based source of preformed DHA, as microalgae produce DHA directly without the conversion step.
What are the sustainability considerations around DHA sources?
Marine-derived DHA depends on fisheries or aquaculture systems.
Algae-derived DHA represents a marine-independent alternative.
Plant-based omega-3 nutrition based on ALA offers another pathway that does not rely on marine biomass extraction.
Written by the Dafee Science Team — published 12/03/2026. 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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