Vegetarians can get omega-3 fats mainly as ALA (alpha-linolenic acid) from ground flaxseed, chia seeds, walnuts, rapeseed oil and soya products. The catch is that the body converts only a small share of ALA into EPA and DHA, the long-chain omega-3s found in oily fish, with reported conversion rates of less than 15 percent according to the US Office of Dietary Supplements. Algae oil is the main vegetarian and vegan source of ready-made DHA, and in some products EPA as well.
This article explains the three main omega-3 fats, which plant foods supply them, how much you would need to eat, what the conversion problem means in practice, and when it is worth talking to a GP or dietitian about algae oil.
In short
- ALA is the plant omega-3, while EPA and DHA are the long-chain omega-3s found mainly in oily fish.
- A tablespoon of flaxseed oil provides about 7.3 g of ALA, according to the US Office of Dietary Supplements.
- The body turns less than 15 percent of ALA into EPA and DHA, so plant sources alone give little of these fats.
- Algae oil supplements usually provide around 100 to 300 mg of DHA per serving, and some also contain EPA.
- EFSA considers 250 mg of EPA and DHA a day an adequate intake for healthy adults.
What are ALA, EPA and DHA?
Omega-3s are a family of polyunsaturated fats. Three of them matter most for everyday nutrition. ALA is a shorter omega-3 found in plants, for example in flaxseed, chia seeds, walnuts and rapeseed oil. It is an essential fat, which means your body cannot make it and you need to get it from food.
EPA and DHA are long-chain omega-3s. They are found mainly in oily fish such as salmon, mackerel, sardines, herring and trout, and in smaller amounts in eggs and some meat. Fish get them from the algae at the bottom of the marine food chain, which is why algae are also the source used for vegetarian supplements. DHA is an important building block of the brain and the retina of the eye.
In the UK, general advice is to eat at least two portions of fish a week, one of them oily. If you do not eat fish, it is worth thinking about where your omega-3s come from. Our overview of whether you are getting enough omega-3 from your diet covers the topic for everyone, including fish eaters.
Which vegetarian foods contain omega-3?
The table shows ALA amounts in common foods, based on figures from the US Office of Dietary Supplements. An ounce is about 28 grams, roughly a small handful.
| Food | Portion | ALA (approx.) | Easy ways to use it |
|---|---|---|---|
| Flaxseed (linseed) oil | 1 tablespoon | 7.3 g | Cold in salad dressings or stirred into yoghurt; not for frying |
| Chia seeds | About 28 g | 5.1 g | Chia pudding, sprinkled on porridge |
| Walnuts | About 28 g | 2.6 g | Snack, salads, baking |
| Whole flaxseed | 1 tablespoon | 2.4 g | Best ground, on cereal or in smoothies |
| Rapeseed (canola) oil | 1 tablespoon | 1.3 g | Everyday cooking and dressings |
| Soybean oil | 1 tablespoon | 0.9 g | Cooking |
The same fact sheet gives an adequate intake for ALA of 1.1 g a day for women and 1.6 g a day for men. A spoonful of ground flaxseed on your breakfast or a small handful of walnuts already covers this. Ground flaxseed is easier to absorb than whole seeds, which often pass through the gut undigested. Store flaxseed oil and ground flaxseed in the fridge, because omega-3 fats go rancid quickly.
Other foods contain smaller amounts of ALA, including tofu, edamame beans, hemp seeds and green leafy vegetables. Eggs, especially those from hens fed an omega-3-enriched diet, provide some DHA for vegetarians who eat them.
Why is ALA not the same as fish omega-3?
Your body can turn ALA into EPA and then into DHA, mainly in the liver, but the process is inefficient. The US Office of Dietary Supplements reports conversion rates of less than 15 percent and concludes that eating EPA and DHA directly from foods or supplements is the only practical way to raise their levels in the body.
In practical terms, this means that eating plenty of flaxseed and walnuts covers your ALA needs well, but it does not give you the same amount of EPA and DHA as a portion of oily fish. How much this matters for an individual healthy adult is not fully clear, and many vegetarians eat a well-balanced diet without supplements. It becomes more relevant in situations where DHA needs are higher, such as pregnancy and breastfeeding.
Does the type of fat you eat make a difference?
ALA and omega-6 fats, which are found in sunflower and corn oil, use the same enzymes for conversion. Some experts suggest that choosing rapeseed oil instead of sunflower oil for everyday cooking is a simple way to improve the balance. This is a sensible kitchen habit rather than a proven fix, but it costs nothing.
What about algae oil?
Algae oil is made from microalgae grown in tanks and is the main source of ready-made DHA that is suitable for vegetarians and vegans. The US Office of Dietary Supplements notes that algae oil supplements usually provide around 100 to 300 mg of DHA, that some also contain EPA, and that one small study found DHA from algae oil was as available to the body as DHA from cooked salmon.
The European Food Safety Authority considers 250 mg of EPA and DHA a day an adequate intake for heart health in healthy adults. EFSA has also concluded that supplemental intakes of EPA and DHA combined of up to 5 g a day do not raise safety concerns for adults. In the UK and the EU, products that meet the conditions may state that EPA and DHA contribute to the normal function of the heart, with the beneficial effect obtained with a daily intake of 250 mg of EPA and DHA. Foods that are a source of ALA may state that ALA contributes to the maintenance of normal blood cholesterol levels, with the beneficial effect obtained with a daily intake of 2 g of ALA.
If you consider an algae oil, check the label for the amount of DHA and EPA per daily dose, whether the capsule shell is plant-based or made from gelatine, and whether the product is labelled as vegetarian or vegan. For readers who know the LR range, please note that LR Super Omega capsules are based on fish oil and are therefore not suitable for vegetarians. Our guide to fish oil and what to check is aimed at people who do eat fish.
Who should think more carefully about omega-3?
Most vegetarian adults who regularly eat ALA-rich foods do not need to worry. However, some groups may want to look at their intake more closely:
- People who are pregnant or breastfeeding, because DHA is needed for the baby’s developing brain and eyes. The US Dietary Guidelines quoted by the Office of Dietary Supplements advise vegetarian and vegan pregnant women to ask a health professional whether EPA and DHA supplementation is necessary.
- Vegans, who do not eat eggs or dairy and so get no DHA from food at all.
- Older adults and people with a limited or restrictive diet.
- Children on a vegetarian or vegan diet, whose needs should be discussed with a GP or health visitor.
When should you see a doctor?
Omega-3 supplements are generally well tolerated, but there are situations where you should speak to your GP or pharmacist first. Ask before taking omega-3 supplements if you take blood-thinning medicines such as warfarin, if you have a bleeding disorder or are due to have surgery, if you are pregnant or breastfeeding, or if you have a long-term health condition. The US Office of Dietary Supplements notes that high doses of EPA and DHA may increase bleeding time.
Seek advice from your GP or a registered dietitian if you are planning a vegetarian or vegan diet for a child, if you have lost weight without trying, or if you are worried that your diet may be missing important nutrients such as vitamin B12, iron or iodine as well as omega-3.
Frequently asked questions
Is flaxseed enough for a vegetarian?
Flaxseed easily covers the recommended intake of ALA. It provides little EPA and DHA, so whether you also want an algae oil depends on your situation. Discuss it with a health professional if you are pregnant or breastfeeding.
Do eggs contain omega-3?
Eggs contain small amounts of DHA, and eggs from hens fed an omega-3-enriched diet contain more. They are a useful source for vegetarians who eat them.
Can I cook with flaxseed oil?
Flaxseed oil is best used cold, because heat damages its delicate fats. Use rapeseed oil for cooking and flaxseed oil for dressings or drizzling over finished dishes.
Is algae oil safe?
Algae oil is generally well tolerated. As with any supplement, follow the dose on the label and speak to your GP or pharmacist if you take medicines, especially blood thinners.
Where does the fish oil in supplements come from?
Fish oil comes from oily fish, which get their EPA and DHA from algae in their diet. Algae oil skips the fish and goes straight to the original source.
Sources
- NIH Office of Dietary Supplements: Omega-3 fatty acids fact sheet for health professionals
- EFSA: EFSA assesses safety of long-chain omega-3 fatty acids (2012)
- European Commission: EU Register of nutrition and health claims
Food supplements are not medicines and do not replace a varied, balanced diet and a healthy lifestyle. This article is general information and not medical advice; if you have symptoms or take medication, please speak to your GP or pharmacist.