Omega-3: why EPA and DHA matter so much
What is omega-3, really?
Omega-3 is a family of polyunsaturated fatty acids. Three of them dominate the discussion: ALA, EPA and DHA.
- ALA (alpha-linolenic acid) is found in the plant kingdom – rapeseed oil, flaxseed and walnuts. It is essential, meaning something you must get through your diet.
- EPA (eicosapentaenoic acid) is found mainly in oily fish and shellfish.
- DHA (docosahexaenoic acid) is also found in fish and is the fatty acid the brain and eyes contain the most of.
The body can make EPA and DHA from ALA, but the conversion is inefficient. Studies suggest that only around 5–10 percent of ALA becomes EPA, and even less becomes DHA. That is why fish – or supplements – are considered the reliable source of EPA and DHA specifically.
The difference between omega-3 and omega-6 often causes confusion. Both are polyunsaturated and both are needed. The problem is the balance: the modern diet is rich in omega-6 from vegetable oils and processed food, while omega-3 is often neglected. That is why the advice focuses on raising the intake of omega-3 specifically, not on cutting fat in general.
How does omega-3 work in the body?
The fatty acids are built into cell membranes and affect how flexible and functional the cells are. In the brain and retina, where the levels are highest, DHA plays a structural role. EPA is used more as a raw material for short-lived signalling molecules involved in the body's normal regulation of inflammation and blood flow.
Because the fatty acids sit in the membranes, it takes time to change the levels. A couple of weeks of intake raises blood values, but replenishing the stores in the tissues takes months. That explains why studies almost always measure effects after 8–12 weeks and why single doses make no difference.
What benefits do EPA and DHA have?
The EU food authority, EFSA, has reviewed the research and authorised several health claims. These are the effects with the strongest support:
- EPA and DHA contribute to the normal function of the heart (at at least 250 mg per day).
- DHA contributes to the maintenance of normal brain function (at at least 250 mg of DHA per day).
- DHA contributes to the maintenance of normal vision (at at least 250 mg of DHA per day).
- In pregnant women, DHA contributes to the normal development of the brain and eyes of the foetus.
Beyond this, there is broad research on omega-3 and blood lipids, mood and joint problems. In a large Cochrane review from 2020, researchers saw small or uncertain effects on the risk of cardiovascular disease, while blood triglycerides fell. The picture is therefore nuanced: the authorised claims are about supporting normal function, not preventing disease.
Why is ALA from plants not enough?
Rapeseed oil and flaxseed are good foods, but they do not meet the whole need. Because the conversion from ALA to EPA and DHA is so limited, you can eat plenty of ALA and still have low levels of DHA in the blood. That is why authorities in the Nordic region recommend fish as the main source – and why most supplements contain ready-made EPA and DHA rather than ALA.
Suspect you are running low? Read our review of 9 signs of omega-3 deficiency.
EPA and DHA contribute to the normal function of the heart – MSC-certified fish oil with 180 mg EPA and 120 mg DHA per capsule.
See current price »How much omega-3 do you need per day?
EFSA's reference intake for adults is 250 mg of EPA and DHA per day. Pregnant and breastfeeding women are recommended an additional 100–200 mg of DHA. Here are the benchmarks:
| Group | EPA + DHA per day |
|---|---|
| Adults | 250 mg |
| Pregnant and breastfeeding | 250 mg + 100–200 mg extra DHA |
| Children 2–18 years | 250 mg |
If you want to go deeper into the numbers – including what applies at high doses – you will find it all in our guide on omega-3 dosage.
Which foods contain the most EPA and DHA?
Oily fish is by far the best source. Salmon, mackerel, herring and sardines each provide around 1–3 grams of EPA and DHA per 100 grams. Leaner fish such as cod provide considerably less, often under 0.3 grams. Health authorities advise eating fish 2–3 times a week, of which oily fish at least once.
Eggs and meat from grass-fed animals contribute small amounts. For those who do not eat fish, algae oil is a plant-based source of both EPA and DHA.
A common mistake is to rely on flaxseed oil. It is rich in ALA, but because the conversion to EPA and DHA is so small, it is not enough to meet the need on its own. See it as a complement, not a replacement for fish or algae oil.
What does the research say about cardiovascular health?
Here the picture is more nuanced than the headlines sometimes suggest. EFSA's authorised claim is that EPA and DHA contribute to the normal function of the heart at 250 mg per day – it is about supporting normal function, not preventing disease.
When it comes to actually reducing the risk of cardiovascular disease, the results are mixed. In the 2020 Cochrane review, researchers saw little or no clear effect on mortality, but blood triglycerides fell at higher doses. The conclusion is that omega-3 is one piece of a healthy lifestyle, not a medicine. The combination of a good diet, exercise and not smoking carries the most weight.
Do you need a supplement?
If you eat oily fish two to three times a week, you probably meet the need. Many people do not – in practice, a large share of us fall well short. Then a fish oil supplement is an easy way to reach 250 mg of EPA and DHA per day. VitaNord Omega-3 provides 180 mg of EPA and 120 mg of DHA per capsule, from MSC-certified fisheries.
Want to compare different options before choosing? See our review of the best omega-3 supplements. And if you are curious about how the two fatty acids differ, read EPA vs DHA.
Frequently asked questions
What is the difference between omega-3 and fish oil?
Omega-3 is an umbrella term for a group of fatty acids, including ALA, EPA and DHA. Fish oil is a source of omega-3 and contains mainly EPA and DHA. A fish oil supplement is therefore a way to get those long-chain omega-3 fatty acids specifically, not a nutrient in its own right.
How quickly do you notice the effect of omega-3?
The levels of EPA and DHA in the blood begin to rise within a few weeks, but the fatty acids are built into cell membranes gradually. In studies, effects are often measured after 8 to 12 weeks of daily intake. So expect to take omega-3 regularly over several months, not on individual days.
Can vegetarians get enough EPA and DHA?
Yes, but it is harder. Plant sources such as flaxseed and walnuts contain ALA, which the body only converts into EPA and DHA to a small degree. Supplements based on microalgae, on the other hand, contain ready-made EPA and DHA and are a common option for those who do not eat fish.
Is omega-3 good for the heart?
EPA and DHA contribute to the normal function of the heart, according to EFSA's authorised health claim. The effect applies at a daily intake of at least 250 mg of EPA and DHA combined. The research on protection against cardiovascular disease is more mixed, so see omega-3 as part of the whole, not an insurance policy.
Sources
- EFSA – Scientific Opinion on Dietary Reference Values for fats, including omega-3 (EFSA Journal 2010)
- EFSA – Scientific Opinion on the Tolerable Upper Intake Level of EPA, DHA and DPA (EFSA Journal 2012)
- Livsmedelsverket (Swedish Food Agency) – Fats: omega-3 and omega-6
- Livsmedelsverket – Advice on fish
- Abdelhamid et al. – Omega-3 fatty acids for the primary and secondary prevention of cardiovascular disease (Cochrane, 2020)
- Nordic Nutrition Recommendations, NNR 2023