Do vegans need omega-3? Algae oil vs fish oil

The objection

“Fish is the only real source of EPA and DHA. The plant omega-3 barely converts, so vegans go short of the fats the brain needs, and in pregnancy that matters most of all.”

The answer

Most of the biology in that objection is right. Flax, chia, walnuts and hemp supply ALA, an essential omega-3, and the body can turn some of it into the long-chain forms EPA and DHA. Tracer studies show that the first step is limited in men and the step on to DHA is very low; women convert more, which may be an effect of oestrogen, and eating more ALA raises EPA in the blood without raising DHA (Burdge & Calder, 2005) [1]. The British Dietetic Association says the conversion “happens slowly and only small amounts are formed”, and that DHA is important for the development of a baby’s brain and eyes [2]. A 2017 systematic review noted that vegetarians can have omega-3 indices up to 60% lower than people who eat marine foods [3].

Where the objection goes wrong is in crediting the fish. In the BDA’s words, “the omega-3 in fish comes from micro-algae” [2], the primary producers of DHA in the marine food chain [3], and an algae oil supplement takes the same fats straight from the source. A 2025 analysis of a randomised trial, written by scientists at an algal-oil manufacturer, found that dose for dose, algal oil raised blood DHA and EPA as well as fish oil [4]. In 74 adults with raised blood fats who took capsules for 14 weeks, dose-adjusted plasma DHA plus EPA on algal oil was 111% of that on fish oil, with a 90% confidence interval of 94 to 132%, which passed the trial’s test for being no worse [4]. The authors list the limits themselves: a small group of mostly white, overweight, middle-aged adults, measured in blood plasma rather than red cells or tissue [4].

The older evidence points the same way. A 2008 study found algal DHA capsules matched cooked salmon: in 32 adults given 600mg of DHA a day for two weeks, plasma DHA rose by about 80% and red-cell DHA by about 25% on either [5]. The 2017 review found that all four randomised trials and both cohort studies of algal DHA in vegetarians, vegans included, reported higher DHA levels [3]. In a 2006 trial, 114 vegetarians took 0.94g of algal DHA or an olive oil placebo daily for eight weeks; the DHA group’s blood triglycerides fell by 23%, though their LDL cholesterol rose, and the oil was well tolerated [6].

How much omega-3 does a vegan need?

The European Food Safety Authority (EFSA) set an adequate intake for adults of 250mg of EPA and DHA combined a day, alongside ALA at 0.5% of energy (2010) [7]. ALA is easy to get from food, and these portions come from US Department of Agriculture food data [8]:

Food	Portion	ALA
Ground flaxseed (linseed)	1 tablespoon (7g)	1.6g
Hulled hemp seeds	1 tablespoon (10g)	0.9g
Walnuts	1oz, 28g (about 14 halves)	2.6g
Chia seeds	1oz, 28g	5.1g

EPA and DHA are harder. Without fish, the BDA points to foods with omega-3 added and to supplements, some of which contain only algae and suit vegans [2]. The simple way to cover it is to take an algae oil supplement giving around 250mg of EPA and DHA combined a day, which matches the European adequate intake for adults, with an extra 100 to 200mg of DHA in pregnancy and breastfeeding [7]. For women who start pregnancy with a low intake, a 2024 guideline advises more; see the pregnancy section below. The BDA does not go that far. The BDA’s fact sheet (2021, now under review) says omega-3 supplements are not recommended for the UK general population because the evidence of benefit is inconclusive, and suggests about 450mg of EPA and DHA a day for anyone who chooses one [2]. The US Academy of Nutrition and Dietetics’ 2025 position is that appropriately planned vegan diets can be nutritionally adequate for adults [9], and omega-3 is part of that planning.

Is more omega-3 better?

Bigger doses are not better: in heart trials, supplements above a gram a day were linked to a higher risk of atrial fibrillation, an irregular heart rhythm. A 2021 meta-analysis of seven trials with 81,210 people, average age 65 and followed for about five years, linked marine omega-3 supplements to a 25% higher relative risk of atrial fibrillation, 49% higher in trials giving more than a gram a day and 12% higher in trials giving a gram or less; it gives no pooled absolute figure [10]. None of these trials tested a dose as low as 250mg. Whether supplements protect the heart at all is disputed: the BDA calls the evidence inconclusive [2], while the US National Center for Complementary and Integrative Health cites a 2019 review concluding that a gram a day brings some cardiovascular benefit [11]. The same centre warns that omega-3 supplements may interact with drugs that affect blood clotting, such as anticoagulants (“blood thinners”) [16], so if you take one of those or any other prescribed medicine, or have a heart rhythm problem, ask a GP or pharmacist before starting any supplement, and don’t change or stop a medicine without speaking to your GP.

Do vegans need more DHA in pregnancy?

For pregnancy, a 2024 international clinical guideline advises every pregnant woman to get at least 250mg a day of DHA plus EPA and a further 100 to 200mg of DHA [12]. Women with a low intake, which includes any vegan who isn’t already supplementing, should take about 600 to 1,000mg a day from no later than about 20 weeks until about 37 weeks, the dose that reduced preterm and early preterm birth in trials [12]. Algae oil is the obvious way to get it, and a midwife or GP can confirm the dose. A 2024 review of how to meet that guidance sustainably, by authors who include advisers to nutrition companies, notes that algal oils suit vegetarians and vegans, have long been used in infant formula and have raised DHA levels in pregnant women [13]. Algae oil also avoids the reason the NHS limits oily fish to two portions a week in pregnancy: tuna and oily fish can contain pollutants, including mercury [14]. The NHS’s own pregnancy supplement advice covers folic acid and vitamin D and does not mention omega-3, but it does say never to take cod liver oil or any supplement containing vitamin A while pregnant, so check the label [15]. The rest of the planning for a vegan pregnancy has its own page.