In short:
- Omega-3 fatty acids cover three main types: ALA (plant-based), EPA and DHA (oily fish, marine oils).
- Authorised claims: EPA and DHA contribute to normal heart function (250 mg a day), DHA alone to normal brain function and normal vision (250 mg a day), ALA to normal blood cholesterol levels (2 g a day).
- Oily fish, rapeseed and flaxseed oil, walnuts and flaxseeds are good sources.
- As a supplement, look at the amount of EPA and DHA per dose, the freshness (TOTOX value) and the oil’s certification.
Omega-3 fatty acids come up in almost every conversation about diet and heart health, often with promises that go well beyond what is actually established. This fact sheet sets out what is established: the role of each type of omega-3, the recommended intakes and what sets a good supplement apart from another.
Omega-3 at a glance
| Benchmark | Value |
|---|---|
| Family | Polyunsaturated fatty acids (ALA, EPA, DHA) |
| Authorised claims | Normal function of the heart (EPA and DHA), normal brain function and vision (DHA), normal blood cholesterol levels (ALA) |
| Benchmark for the heart | 250 mg of combined EPA and DHA a day |
| Benchmark for the brain and vision | 250 mg of DHA a day |
| Benchmark for cholesterol levels | 2 g of ALA a day |
| Food sources | Oily fish, rapeseed, flaxseed and walnut oils, flax and chia seeds |
The role of omega-3 in the body
Omega-3 fatty acids are not a single group: they are three fatty acids with distinct roles, each recognised separately in the EU register of nutrition and health claims1.
- EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid) contribute to the normal function of the heart, for a combined intake of 250 mg a day.
- DHA, on its own, also contributes to the maintenance of normal brain function and normal vision, again at 250 mg a day.
- ALA (alpha-linolenic acid), the plant-based omega-3, contributes to the maintenance of normal blood cholesterol levels, for an intake of 2 g a day.
No other claim is authorised: omega-3 fatty acids do not “boost” immunity and do not replace treatment for inflammation or cholesterol. These are measured contributions, within an overall healthy diet and lifestyle.
How much omega-3 do you need per day?
| Reference | Value per day |
|---|---|
| Combined EPA and DHA, heart claim benchmark | 250 mg |
| DHA alone, brain and vision claim benchmark | 250 mg |
| ALA, cholesterol claim benchmark | 2 g |
These benchmarks concern total intake, including food, and do not add up to each other: a product providing 250 mg of DHA covers both the heart benchmark (alongside EPA) and the brain and vision benchmark. ANSES publishes broader reference values on fats and fatty acids2, useful for placing these benchmarks within the overall diet.
The best food sources of omega-3
EPA and DHA are found almost exclusively in marine products; ALA mostly comes from plant oils and seeds.
| Food | Omega-3 provided |
|---|---|
| Oily fish (salmon, mackerel, sardine, herring) | EPA and DHA |
| Rapeseed oil, flaxseed oil | ALA |
| Flax and chia seeds | ALA |
| Walnuts | ALA |
| Fish and algae oils (supplements) | EPA and DHA |
The national nutrition health programme’s benchmark is to eat fish twice a week, including one oily fish, to cover part of your EPA and DHA needs. For the exact content of each food, use the ANSES Ciqual table3. The article on micronutrition and diet explains how to build a diet balanced in fatty acids.
Forms of omega-3 in supplements
An omega-3 supplement is best chosen on two technical criteria, far more than on the packaging.
The amount of EPA and DHA per dose
Most fish oils display a percentage of total omega-3, but what matters is the actual amount of EPA and DHA per capsule or per dose, since these are the two forms that carry the claims. An oil “rich in omega-3” can still provide little EPA and DHA if it is diluted in a base oil.
Freshness and purity
| Benchmark | What to know |
|---|---|
| TOTOX value | Measures oil oxidation; the lower it is, the fresher the oil |
| IFOS certification | Independent check of purity (heavy metals, pollutants) and of the actual EPA and DHA concentration |
| Fish oil | The most common source of EPA and DHA |
| Krill oil | Another marine source of EPA and DHA, often described as better absorbed, with no distinct claim to date |
| Algae oil | The only vegan source of direct EPA and DHA, useful for a fish-free diet |
| Plant oil (rapeseed, flax) | A source of ALA only, no direct EPA or DHA |
Some French supplement brands, such as Nutripure, state the raw material used on their labels (for example an EPAX oil), which makes it possible to check traceability and the EPA and DHA concentration. The guide on how to choose a food supplement brand details how to read the label.
Omega-3, the brain and pregnancy
DHA is an important structural component of the brain and the retina, which explains the claims on brain function and vision. During pregnancy and breastfeeding, the mother’s DHA needs increase, and the EU register recognises a specific claim on the contribution of maternal DHA intake to the normal development of the eye and brain of the foetus and the breastfed infant.
To place omega-3 among the other nutrients worth watching, the guide on vitamin and mineral needs reviews the official reference values, and the magnesium fact sheet completes this directory of the most sought-after actives.
Precautions for use
- Anticoagulant or antiplatelet treatment: ask your doctor before taking a high-dose omega-3 supplement.
- Allergy to fish or shellfish: choose an algae oil instead, which contains neither fish nor shellfish.
- Before surgery: tell your doctor or surgeon about any omega-3 supplement you are taking.
- Stick to the dose stated on the label, especially if you also take other supplements or fortified foods.
For athletes, the sports nutrition guide reviews the supplements with a recognised effect, alongside omega-3.
Frequently asked questions
What are omega-3 fatty acids for?
Under the EU register of claims, EPA and DHA contribute to the normal function of the heart, DHA contributes to the maintenance of normal brain function and normal vision, and ALA contributes to the maintenance of normal blood cholesterol levels. These are the only authorised claims on omega-3 fatty acids.
How much omega-3 do you need per day?
The authorised claims are based on 250 mg of DHA a day for the heart, brain function and vision, 250 mg of combined EPA and DHA a day for the heart, and 2 g of ALA a day for cholesterol levels. These are label benchmarks, including food.
What is the difference between ALA, EPA and DHA?
ALA is a plant-based omega-3 (rapeseed oil, flaxseed oil, walnuts) that the body converts in small part into EPA and then DHA. EPA and DHA are found directly in oily fish and marine oils, and are the two forms linked to the heart claims; DHA alone carries the claims on brain function and vision.
How do you choose a quality omega-3 supplement?
Look at the actual amount of EPA and DHA per dose, not just the total weight of fish oil. A low TOTOX value signals a fresh, less oxidised oil, and a certification such as IFOS attests to purity checks for heavy metals and pollutants.