What Is ALA (Alpha-Linolenic Acid)?
ALA (alpha-linolenic acid) is a short-chain omega-3 fatty acid with 18 carbon atoms. It is the form of omega-3 found in plant foods: flaxseeds, chia seeds, walnuts, and hemp seeds. ALA is classified as an essential fatty acid because your body cannot synthesise it. You must get it from your diet.
The critical distinction between ALA and the long-chain omega-3s (EPA and DHA) is that your body must convert ALA before it can use it for the physiological functions cited in health claims. That conversion is inefficient and sex-dependent.
Tracer studies show men convert roughly 8% of ALA to EPA and under 4% to DHA, while women convert up to 21% and 9% respectively. We covered the full comparison in our ALA vs EPA vs DHA article.
ALA has its own EFSA-authorised health claim: ALA contributes to the maintenance of normal blood cholesterol levels, at a daily intake of 2 g (EU 432/2012). This is a different claim from the heart, brain, and vision claims attached to EPA and DHA. We list all authorised claims in our EFSA claims reference.
Why ALA Alone Does Not Replace EPA and DHA
If you are scanning supplement labels in a shop, you will sometimes see products marketed as "omega-3" that contain only ALA from flaxseed or hemp oil. They are not lying; ALA is an omega-3.
But labelling a flaxseed oil capsule as an omega-3 supplement while implying the cardiovascular and brain benefits associated with EPA and DHA is misleading. Those EFSA claims require preformed EPA and DHA at 250 mg daily. ALA does not qualify for them.
A capsule of flaxseed oil, however large the dose, cannot guarantee that your body will convert enough ALA into the long-chain forms that matter. For men especially, the DHA conversion is so poor that no realistic ALA dose compensates for it.
For anyone on a plant-based diet, this means checking your supplement label for EPA and DHA content separately, not just "omega-3." We chose to manufacture algae-based EPA and DHA (using Nannochloropsis gaditana for EPA and Schizochytrium for DHA) specifically because these species produce the preformed long-chain fatty acids directly, bypassing the conversion step entirely.
That approach costs more than a flaxseed oil capsule, and algae-based supplements carry a price premium that is not trivial. But it is the only plant-based route that reliably delivers what the EFSA evidence actually requires.
ALA at a Glance
- Full name: Alpha-linolenic acid (C18:3 n-3)
- Type: Short-chain omega-3 polyunsaturated fatty acid, essential
- Food sources: Flaxseeds, chia seeds, walnuts, hemp seeds and their oils
- Conversion to EPA: Roughly 8% in men, up to 21% in women
- Conversion to DHA: Under 4% in men, up to 9% in women
- EFSA claim: Normal blood cholesterol levels at 2 g daily
What our research found
We reviewed published tracer studies and controlled supplementation trials to understand the practical ceiling of ALA conversion. Two findings shaped how we think about plant-based omega-3 intake.
The conversion gap depends on your sex, and the difference is large enough to matter in practice. Women convert roughly 21% of ALA to EPA and 9% to DHA. Men convert about 8% to EPA and 0 to 4% to DHA. The difference is driven by oestrogen, which upregulates the desaturase enzymes that elongate the ALA chain.
If you are a vegan woman taking flaxseed oil and wondering whether it covers you, the honest answer is: possibly for EPA, almost certainly not for DHA.
Even flaxseed oil at 55 to 60% ALA cannot reliably raise blood DHA. When we looked at supplementation studies, increasing dietary ALA raised blood EPA and DPA modestly but produced no detectable DHA increase in most participants. That is not a marginal shortfall; it is a category failure for anyone relying on ALA alone to meet the 250 mg EPA+DHA daily threshold.
When we selected Schizochytrium for our DHA product, this conversion data was the deciding factor. We reviewed published fatty acid profiles across candidate algae species. Schizochytrium produces DHA at 30 to 40 per cent of total fatty acids under optimised conditions, comparable to fish oil concentration and achievable without any fish in the supply chain.
That is the arithmetic that makes algae the only credible plant-based DHA source at supplement doses.
Sources
- Burdge GC, Calder PC. Conversion of alpha-linolenic acid to longer-chain polyunsaturated fatty acids in human adults. Reproduction, Nutrition, Development. 2005;45(5):581–597. PubMed
- Brenna JT et al. alpha-Linolenic acid supplementation and conversion to n-3 long-chain polyunsaturated fatty acids in humans. Prostaglandins, Leukotrienes and Essential Fatty Acids. 2009;80(2–3):85–91. PubMed
- Commission Regulation (EU) No 432/2012 establishing a list of permitted health claims made on foods. 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 EPA and DHA supplements from microalgae. We have a commercial interest in the distinction between ALA and long-chain omega-3. Conversion rates reflect published nutrition science. The EFSA claim is from Commission Regulation (EU) No 432/2012.
Last reviewed: March 2026
