ALA, EPA and DHA: Differences and the Limits of Conversion
ALA, EPA and DHA are three different omega-3 fats. See where each comes from, what the research tested, and why the body's ALA-to-EPA-and-DHA conversion is debated.
Content last updated . This page has not been medically reviewed.
Overview
The word "omega-3" covers three fats that are often treated as one. NCCIH explains that most research has focused on EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid), found in seafood and fish oil, while ALA (alpha-linolenic acid) is found in plant oils such as flaxseed, soybean and canola, and in chia seeds and walnuts. [1] EPA and DHA are called "long-chain" omega-3s. ALA is a shorter plant fat. Findings for one should not be assumed for the others.The three side by side
| ALA | EPA | DHA | |
|---|---|---|---|
| Main sources | Flaxseed, soybean and canola oils, chia seeds, walnuts [1] | Oily fish, shellfish, fish oil; some algal oils [1] | Oily fish, fish oil, algal oil [1] |
| Supplement products | Flaxseed oil [1] | Fish oil; the prescription medicine Vascepa contains only EPA [2] | Fish oil; algal oils are a vegetarian source of DHA [1] |
| What big reviews found | Cochrane (2020): ALA probably makes little or no difference to all-cause or cardiovascular death, and may slightly lower cardiovascular events and arrhythmia [3] | Cochrane (2020): see the long-chain results below [3] | Same long-chain pooled results; trials often tested EPA and DHA together [3] |
Can the body make EPA and DHA from ALA?
The body can convert some ALA, but how much counts is debated. Proper evidence for one clear number was not found, and the sources disagree in tone.- A 2022 review by a University of Southampton researcher argued that the claim that conversion is "constrained" is inaccurate, and that conversion may be nutritionally adequate. It also noted that study designs differ widely and that results lack replication. This is an opinion piece. [4]
- A study of 14,422 UK adults found vegetarians and vegans had total omega-3 intakes of 57 to 80% of fish-eaters but status differences that were smaller than expected, and a higher estimated conversion ratio in non-fish-eaters and in women. [5]
- A 2026 systematic review of 45 studies found vegetarian diets, particularly vegan, had significantly lower blood EPA and DHA, and that DHA from microalgae oil improved DHA status, especially in pregnancy and lactation. [6]
Practical reading: mixed. If you eat no fish, plant ALA contributes something, but the evidence does not show it matches the direct EPA and DHA found in fish or algal oil. Ask a clinician or dietitian about your own situation, especially in pregnancy. See algal oil and vegetarian and vegan supplements.
What the heart research found, by type
The 2020 Cochrane review of 86 trials (162,796 adults, 12 to 88 months) separated the two groups. Increasing long-chain omega-3 had little or no effect on all-cause death (risk ratio 0.97) or cardiovascular events (0.96), and slightly lowered coronary heart disease events (0.91, low certainty) and triglycerides (about 15%). [3] For ALA, effects on deaths and coronary events were close to none, with a slight reduction in cardiovascular events and arrhythmia (low to moderate certainty). [3] Details: Omega-3 evidence by use.Amounts
Intake values differ by country. EFSA (EU) gives 250 mg a day of EPA plus DHA as an adequate intake for general cardiovascular health. [7] The NHS (UK) frames it as fish portions rather than milligrams: at least two a week, one of them oily. [8] Amounts used in trials are study amounts, not recommendations.Safety
EPA and DHA concentrates can affect bleeding and heart rhythm at high doses; see Omega-3 safety and interactions and medication interactions.Frequently asked questions
Is ALA as good as fish oil?
Not shown. Reviews tested them separately, and the direct EPA and DHA conversion from ALA is debated. [3][4]
Which is best for vegetarians?
A systematic review found algal DHA improved DHA status in vegetarians, particularly in pregnancy and breastfeeding. [6]
Does it matter whether a product has EPA or DHA?
Trials differ: the prescription Vascepa is EPA only, while Lovaza is mainly EPA and DHA. They are medicines tested for specific conditions, not interchangeable with supplements. [2][9]
References
- NCCIH, Omega-3 Supplements: What You Need To Know. Read 2026-10-22.
- FDA-approved prescribing information, Vascepa (icosapent ethyl), DailyMed. Read 2026-10-22.
- Abdelhamid AS et al. Omega-3 fatty acids for the primary and secondary prevention of cardiovascular disease. Cochrane Database Syst Rev 2020. Read 2026-10-22.
- Burdge GC. α-linolenic acid interconversion is sufficient as a source of longer chain ω-3 polyunsaturated fatty acids in humans: an opinion. Lipids 2022. Read 2026-10-22.
- Welch AA et al. Dietary intake and status of n-3 polyunsaturated fatty acids in fish-eating and non-fish-eating meat-eaters, vegetarians and vegans (EPIC-Norfolk). Am J Clin Nutr 2010. Read 2026-10-22.
- Chamorro R et al. Vegetarian diets and their effect on n-3 polyunsaturated fatty acids status in humans: systematic review. Lipids 2026. Read 2026-10-22.
- EFSA, EFSA assesses safety of long-chain omega-3 fatty acids (2012 news story). Read 2026-10-22.
- NHS, Fish and shellfish. Read 2026-10-22.
- FDA-approved prescribing information, Lovaza (omega-3-acid ethyl esters), DailyMed. Read 2026-10-22.
Education, not medical advice. This page is for general information. It does not diagnose or treat any condition and is not a substitute for care from a qualified health professional. Natural does not automatically mean safe. Ask a clinician or pharmacist before changing your care, especially if you take medication, are pregnant or breastfeeding, or have a health condition.