EPA vs DHA: What Is the Difference?
EPA and DHA are both long-chain omega-3 fatty acids, both found in fish and algae, and both cited in the same EFSA health claims. So why does it matter which one you are getting?
Because they are not the same molecule. They concentrate in different tissues and play different biochemical roles.
Most supplements deliver them in very different ratios. When choosing an omega-3 product, the EPA-to-DHA balance is one of the most important things on the label.
The Basic Distinction Between EPA and DHA
EPA (eicosapentaenoic acid) has 20 carbon atoms and five double bonds. DHA (docosahexaenoic acid) has 22 carbon atoms and six double bonds. That structural difference is not trivial. Your body concentrates DHA in the brain and retina, where it forms a significant proportion of cell membrane fatty acid content.
EPA circulates more broadly and is the primary precursor to eicosanoids, signalling molecules involved in the body's inflammatory response pathways.
In practical terms: DHA is a structural component. EPA is a functional one. Your body uses them differently, and the health claims authorised for each reflect that distinction. If you take a capsule each morning without ever checking which of the two it delivers, this is the distinction that decides whether it is doing the job you bought it for.
What the Authorised Health Claims Tell You
The EFSA-authorised claims separate EPA and DHA clearly (Commission Regulation (EU) No 432/2012):
- EPA and DHA together contribute to the normal function of the heart, at a combined daily intake of 250 mg.
- DHA specifically contributes to the maintenance of normal brain function, requiring 250 mg DHA daily.
- DHA specifically contributes to the maintenance of normal vision, also requiring 250 mg DHA daily.
- Maternal DHA contributes to normal foetal brain and eye development, at 200 mg DHA daily on top of the recommended 250 mg EPA+DHA.
Notice what is absent: there is no authorised claim for EPA alone on brain function, and no authorised claim for DHA alone on heart function (the heart claim requires the combination). The regulatory framework treats them as overlapping but not interchangeable.
That matters when you are stood in front of the shelf. If a pack leads on brain function, turn it over and find the DHA figure on its own: 250 mg daily is the threshold that claim rests on, and a combined omega-3 total will not tell you whether the product reaches it.
We cover the full claims list with intake conditions in our EFSA-authorised claims reference.
Why Most Research Studies Them Together
The majority of omega-3 clinical trials use fish oil or combined EPA+DHA supplements, which makes it difficult to attribute specific outcomes to one fatty acid alone. When a study reports that "omega-3 supplementation improved X," the intervention usually contained both EPA and DHA. Isolating the contribution of each requires studies specifically designed with EPA-only or DHA-only arms, and those are less common.
This is worth knowing because supplement marketing often implies that a product containing only one of the two fatty acids delivers the full range of omega-3 benefits. In our assessment, the evidence supports getting both, and the authorised claims reflect that. A supplement that provides EPA without DHA, or DHA without EPA, covers part of the picture.
Where Each One Comes From
In nature, fish accumulate both EPA and DHA from eating microalgae. In the supplement world, the two fatty acids come from different algae species:
EPA: The richest plant source is marine phytoplankton, specifically Nannochloropsis. This species produces EPA as its dominant long-chain fatty acid, with very little DHA. We use Nannochloropsis in our ULTANA Phytoplankton for this reason.
DHA: The most common plant source is algae oil from Schizochytrium, a marine heterotroph that produces DHA abundantly but very little EPA. Most algae-derived DHA capsules on the market use this species. We produce Clean Omega DHA from algae for the DHA side.
Fish oil delivers both in a single product because the fish has accumulated both from the food chain. From plant sources, you typically need two products to cover both fatty acids. That is a genuine inconvenience. We split our own range the same way, ULTANA for EPA and Clean Omega for DHA, because no single algae product covers both well.
How to Read the Label
When you pick up an omega-3 supplement, the number that matters is not "total omega-3." It is the individual EPA and DHA figures per serving. A product advertising "1000 mg omega-3" might contain 500 mg EPA and 300 mg DHA, or 100 mg EPA and 800 mg DHA, or 900 mg ALA and negligible amounts of either.
Those are three very different products solving three very different problems.
If the label shows total omega-3 without breaking out EPA and DHA separately, you cannot evaluate what the product actually delivers. That level of opacity should make you cautious, not reassured.
Which One Do You Need
The answer depends on your specific goal:
- If your priority is heart function: you need combined EPA+DHA at 250 mg daily.
- For brain function or vision: you need DHA specifically, reaching the 250 mg daily threshold.
- During pregnancy or breastfeeding: you need DHA at 200 mg daily on top of the standard EPA+DHA baseline.
- For general omega-3 coverage from plant sources: you need both fatty acids, which means combining an EPA source with a DHA source.
Most health authorities recommend getting both. When we reviewed the omega-3 products on UK shelves against these thresholds, the more useful question turned out to be which of the two your current supplement is short on.
If your omega-3 comes from flaxseed or a generic vegan capsule, you are probably short on both: ALA converts to EPA at roughly 5 to 8 per cent and to DHA at below 1 per cent. Flaxseed is a cheap and genuinely good ALA source; it is the conversion step that fails you, not the seed.
Check the label. If it does not print EPA and DHA separately, replace it.
What our research found
The strongest cardiovascular evidence is for EPA alone, not combined fish oil. The REDUCE-IT trial gave high-risk patients 4 grams per day of pure EPA (icosapent ethyl) and found a 25 per cent reduction in cardiovascular events and a 20 per cent reduction in cardiovascular death. The JELIS trial found EPA-only supplementation reduced major coronary events by 19 per cent.
DHA-only cognitive trials have been less conclusive. Studies in people with advanced Alzheimer's disease found no benefit from DHA supplementation. There is some evidence of benefit in mild cognitive impairment, but not enough to support definitive claims. The brain function case for DHA rests on its structural role in neural membranes, not on trial outcomes. Buy DHA for the structural reason, not the trial data.
Species selection for our products followed the same split as the research. We use Nannochloropsis for EPA because it produces EPA as the dominant long-chain fatty acid across photobioreactor batches. For DHA, Schizochytrium's fermentation process keeps the DHA concentration predictable in a way photosynthetic species at scale cannot. The research distinction between the two fatty acids drove the decision to offer them separately.
Sources
- Swanson D, Block R, Mousa SA. Omega-3 fatty acids EPA and DHA: health benefits throughout life. Adv Nutr. 2012;3(1):1-7. PubMed
- Calder PC. Marine omega-3 fatty acids and inflammatory processes: effects, mechanisms and clinical relevance. Biochim Biophys Acta. 2015;1851(4):469-484. PubMed
- EFSA NDA Panel. Scientific Opinion on DHA and EPA: brain, eye and nerve development, brain function, vision, cardiac function. EFSA Journal. 2011;9(4):2078. EFSA
- Commission Regulation (EU) No 432/2012. Official Journal of the EU. L 136/1. EUR-Lex
Cara Hayes, MSc Nutrition and Dietetics (University of Sydney), writes all content in the Phytality Knowledge Centre. Read our editorial policy.
This article is for informational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Consult your healthcare provider before starting any supplement.
Methodology and Disclosure
Phytality manufactures both an EPA-rich phytoplankton supplement and a DHA algae oil supplement. We have a commercial interest in both fatty acids and in the distinction between them. EFSA health claims are cited from Commission Regulation (EU) No 432/2012 with stated intake conditions.
Biochemical role descriptions reflect established nutrition science. Species-level fatty acid profiles reflect published lipid analyses. The observation about research design reflects our review of the clinical trial landscape.
Last reviewed: March 2026
