EFSA adequate intake + Arterburn 2008 bioequivalence

Vegan vs Vegetarian Omega-3: ALA, EPA, DHA, and Algae Oil

Plant omega-3 starts as alpha-linolenic acid in flax, chia, walnuts, and hemp. The body converts it into the longer-chain EPA and DHA your brain and heart actually use, but the conversion is inefficient. Algae oil closes the gap directly. This page walks through the biochemistry, the dose, and the published evidence for cardiovascular and cognitive outcomes.

The short answer. Vegans should take a daily algae oil supplement supplying 250 to 500 mg of combined EPA and DHA (EFSA adequate intake is 250 mg). Continue to eat ground flaxseed, chia, walnuts, and hemp for ALA and whole-food benefits, but do not rely on conversion alone for EPA and DHA. Vegetarians with omega-3 enriched eggs in their diet may meet the threshold from food; standard eggs and dairy do not.

The conversion problem in one paragraph

ALA from plants must be elongated and desaturated through several enzymatic steps to become EPA, and EPA must be further elongated and desaturated to become DHA. The rate-limiting enzyme is delta-6-desaturase, which is shared with the omega-6 conversion pathway. On a typical Western diet rich in linoleic acid (from soybean, corn, and sunflower oils), the enzyme is saturated with omega-6 substrate and the omega-3 conversion runs slowly. Published estimates (Burdge and Calder 2005, Brenna 2002, others) put the ALA-to-EPA conversion at 5 to 10% and the ALA-to-DHA conversion at under 1% on a Western background diet. Women have modestly higher conversion than men, attributed to oestrogen.

The practical implication: even a generous 3 g per day of ALA from flax and chia yields perhaps 150 to 300 mg of EPA and well under 30 mg of DHA. That is in the right neighbourhood for EPA but well short for DHA, particularly during pregnancy, lactation, and infancy where DHA matters for retinal and neural development. This is why the modern vegan and vegetarian guidance treats algae oil as the practical answer rather than ALA optimisation alone.

ALA-rich plant foods, ranked

Food	Serving	ALA (g)	Notes
Ground flaxseed	1 tbsp (10 g)	2.3	Must be ground; whole seed passes through
Flaxseed oil	1 tsp (5 ml)	2.7	Heat-sensitive, use cold; high concentration
Chia seeds	1 tbsp (12 g)	2.4	Stable whole; gels when soaked
Hemp seeds (hulled)	2 tbsp (20 g)	1.0	Also good complete protein source
Walnuts (English)	30 g (~14 halves)	2.6	Highest ALA among nuts
Rapeseed (canola) oil	1 tbsp (15 ml)	1.3	Stable for cooking; UK and EU staple
Soybean oil	1 tbsp (15 ml)	0.9	High linoleic acid competes with conversion
Edamame (cooked)	1 cup (155 g)	0.3	Useful incremental
Tofu (firm)	100 g	0.4	Useful incremental

A vegan eating 1 tbsp of ground flax with breakfast, a handful of walnuts as a snack, and rapeseed oil cooked vegetables at dinner clears 6 g of ALA easily, which is well above the EFSA adequate intake of 2 g ALA per day. Whether that converts to enough EPA and DHA depends on body, diet background, and need; for safety, supplement.

Algae oil: dose, brands, and what to look for

Algae oil is extracted from cultured microalgae, primarily Schizochytrium and Crypthecodinium species, which produce DHA naturally and some species also produce EPA. The published bioequivalence trials (Arterburn LM, Hall EB, Oken H. Distribution, interconversion, and dose response of n-3 fatty acids in humans, Am J Clin Nutr 2006; Arterburn LM et al. Algal-oil capsules and cooked salmon: nutritionally equivalent sources of docosahexaenoic acid, J Am Diet Assoc 2008) confirm that algae-derived DHA raises serum DHA equivalently to fish-derived DHA milligram for milligram.

Per-supplement, look for the combined EPA plus DHA content on the back of the label, not the total algae oil weight. A typical vegan softgel might be a 1,000 mg algae oil capsule supplying 300 mg DHA and 150 mg EPA, totalling 450 mg combined. Brands carrying vegan EPA plus DHA in the UK and US include Nordic Naturals Algae Omega, Testa Omega-3, Norsan Vegan, Now Foods Algal DHA, Deva Vegan Omega-3, and Vivo Life. Capsule shells should be vegetarian (carrageenan or tapioca) rather than gelatine; check the pack.

Cost note: vegan algae oil typically costs 0.20 to 0.50 GBP or USD per day at the EFSA-target dose. This is more than fish oil per gram of EPA plus DHA but is the only direct vegan option. The price premium is decreasing as algae cultivation scales.

What the cardiovascular and cognitive trials actually say

The cardiovascular evidence base for omega-3 is mixed. The large REDUCE-IT trial (Bhatt DL et al., NEJM 2019; 380: 11) using a high-dose purified EPA pharmaceutical (icosapent ethyl, 4 g per day) showed a 25% reduction in major cardiovascular events in statin-treated patients with elevated triglycerides. The earlier STRENGTH trial using a mixed EPA and DHA preparation did not replicate the benefit. The American Heart Association 2017 science advisory recommends 1 g per day of EPA plus DHA for secondary prevention in established cardiovascular disease, and supports food-based omega-3 (fish or algae) intake for primary prevention. Vegans with diagnosed cardiovascular disease should discuss high-dose algae oil with their cardiology team.

The cognitive evidence is also mixed but suggestive. Meta-analyses of DHA supplementation in older adults (Mazereeuw et al. 2012, Yurko-Mauro et al. 2015) show modest improvements in memory measures, particularly in those with low baseline DHA status. The pre-clinical DHA loading hypothesis for slowing Alzheimer's-type decline has not been confirmed by large trials. The reasonable working position: adequate DHA status throughout life supports brain function, and inadequate DHA status is undesirable, but high-dose DHA is not a cognitive booster.

Pregnancy and lactation is where the DHA case is strongest. Maternal DHA crosses the placenta and is incorporated into fetal brain and retinal membranes; DHA also accumulates rapidly in breast milk. The Cochrane review (Middleton 2018) on omega-3 supplementation in pregnancy found a 11% reduction in early preterm birth (under 34 weeks). A pregnant vegan should be supplementing 200 mg DHA per day on top of any background EPA plus DHA, per the European Commission's expert consensus and the WHO's complementary feeding guidance.

Storage, oxidation, and the rancidity question

All long-chain polyunsaturated fats oxidise. Oxidised omega-3 supplements are not harmful but are not beneficial; the oxidation products replace the active compounds. Algae oil softgels should be stored in their original container, ideally refrigerated after opening, and used within 2 months of opening or by their printed best-before date. A rancid fishy or paint-like smell means the oil has oxidised; throw it out.

Ground flaxseed similarly oxidises rapidly once milled. Buy whole flaxseed, grind it in a coffee grinder as you need it, and store the rest in the fridge. Pre-ground flaxseed in a sealed nitrogen-flushed pack is acceptable but starts to degrade once opened. Chia and walnuts are more stable due to their natural antioxidant content but still benefit from cool storage.

Special situations. Pregnant and breastfeeding vegans should add 200 mg of DHA per day on top of normal supplementation (see pregnancy page). Older adults benefit from confirming DHA status; the EPIC-Norfolk cohort linked low DHA to higher cognitive decline. People on anticoagulants should discuss algae oil dose with their GP because high doses can mildly extend bleeding time.

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Frequently asked questions about omega-3

What is the difference between ALA, EPA, and DHA?

ALA (alpha-linolenic acid) is the parent omega-3 fatty acid found in plant foods (flaxseed, chia, walnuts, hemp). EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid) are the long-chain marine omega-3s that the body uses directly for membrane structure, inflammation regulation, and brain and retina development. Humans can convert ALA to EPA at about 5 to 10% efficiency and ALA to DHA at under 1%. EPA and DHA are essentially the active forms; ALA is the raw material. This is why fish, fish oil, and algae oil are more efficient sources than flax or chia.

Can vegans get enough EPA and DHA from flaxseed?

Partially. A daily tablespoon of ground flaxseed delivers around 2.3 g of ALA, which converts to about 115 to 230 mg of EPA and under 25 mg of DHA at typical conversion rates. This is roughly half the EFSA adequate intake of 250 mg EPA plus DHA. Walnuts, chia, and hemp seeds together can push conversion to the EFSA threshold. The cleaner answer for vegans concerned with brain, eye, or cardiovascular outcomes is to add a daily algae oil supplement (250 to 500 mg EPA plus DHA combined) and continue to eat flax, chia, and walnuts for the broader benefits of those whole foods.

Is algae oil as good as fish oil?

Yes. Fish do not synthesise EPA and DHA themselves; they accumulate it by eating algae and small organisms that eat algae. Algae oil is the source one step closer to the original. Bioequivalence studies (Arterburn et al. 2008 and subsequent trials) show that algae-derived DHA raises serum DHA equivalently to fish oil DHA on a milligram-for-milligram basis. Algae oil avoids the heavy metal contamination concerns (mercury, dioxins, PCBs) that come with some fish oils, and it is suitable for vegans. The cost is higher per gram of EPA plus DHA, typically 1.5 to 3x fish oil pricing.

How much algae oil should a vegan take?

The EFSA adequate intake is 250 mg of EPA plus DHA combined per day for healthy adults, and a slightly higher target of 100 to 200 mg DHA on top during pregnancy and lactation for fetal and infant neural development. Vegan algae oil supplements typically deliver 250 to 500 mg of combined EPA and DHA per softgel. For most adults, 250 to 500 mg daily of combined EPA plus DHA from algae oil is the appropriate dose. People with diagnosed cardiovascular disease may need more (1 to 4 g daily) under medical guidance, per the American Heart Association 2017 advisory.

Why is the ALA to DHA conversion so low?

The enzymatic chain from ALA to DHA goes through several desaturation and elongation steps. The rate-limiting enzyme is delta-6-desaturase, which also competes for omega-6 substrates (linoleic acid). A typical Western diet is rich in omega-6 linoleic acid (from sunflower, corn, soybean oils), which saturates delta-6-desaturase and slows omega-3 conversion. Reducing dietary linoleic acid (using olive, rapeseed, or avocado oil instead of corn or sunflower) modestly improves ALA conversion, but the absolute efficiency remains low. Women tend to convert ALA at slightly higher rates than men, possibly due to oestrogen effects on delta-6-desaturase activity.

Do vegetarians get DHA from dairy or eggs?

Modest amounts. A typical UK egg supplies about 50 mg of DHA (higher in eggs from hens fed omega-3 enriched feed, often marketed as Omega-3 Eggs at 200 to 400 mg DHA per egg). Dairy contributes essentially no DHA. A vegetarian eating two standard eggs a day picks up about 100 mg DHA, below the EFSA 250 mg EPA plus DHA target. Vegetarians who want to ensure adequate intake have two options: switch to omega-3 enriched eggs, or add algae oil. The algae oil route is cleaner because the dose is reliable.

Sources cited. NIH ODS Omega-3 Fatty Acids fact sheet; EFSA Panel on Dietetic Products. Scientific opinion on dietary reference values for fats, EFSA J 2010; 8: 1461; Burdge GC, Calder PC. Conversion of alpha-linolenic acid to longer-chain polyunsaturated fatty acids in human adults, Reprod Nutr Dev 2005; 45: 581-597; Arterburn LM et al. Algal-oil capsules and cooked salmon: nutritionally equivalent sources of docosahexaenoic acid, J Am Diet Assoc 2008; 108: 1204-1209; Bhatt DL et al. Cardiovascular risk reduction with icosapent ethyl for hypertriglyceridemia, NEJM 2019; 380: 11-22; Middleton P et al. Omega-3 fatty acid addition during pregnancy, Cochrane Database 2018; The Vegan Society Omega-3 guidance. All values as of May 2026.