Quick answer
- The NHS advises at least 2 portions of fish a week, 1 of them oily. If you use a supplement instead, UK dietitians suggest about 450 mg of EPA + DHA a day; avoid fish liver oil in pregnancy because of its vitamin A.
- Compare mg of EPA + DHA per daily dose: a standard 1,000 mg fish oil capsule may hold only about 300 mg of omega-3.
- The heart claim starts at 250 mg of EPA + DHA a day; brain and vision claims at 250 mg of DHA.
- EFSA considers up to 5 g a day of supplemental EPA + DHA safe for adults. People with heart disease should ask their GP first.
- Algae oil is the vegan option and raises blood DHA comparably to fish oil, but often has little EPA.
Key numbers
- UK advice (NHS)
- 2 portions of fish a week, 1 oily
- A portion is about 140 g.
- UK supplement guide (BDA)
- About 450 mg EPA + DHA/day
- If you don't eat fish.
- Heart claim (UK and EU)
- 250 mg EPA + DHA/day
- Brain and vision claims (UK and EU)
- 250 mg DHA/day
- Triglycerides / blood pressure claims
- 2 g / 3 g EPA + DHA/day
- Label must warn not to exceed 5 g a day.
- Safe supplemental intake (EFSA)
- up to 5 g EPA + DHA/day
- Typical 1,000 mg fish oil capsule
- ~300 mg EPA + DHA
- Concentrates reach 600 mg or more.
What these terms mean: NRV upper levels (NHS, EFSA) maximum levels by country daily dose
How to choose
- Read the "of which EPA" and "of which DHA" lines per daily dose; ignore the total oil figure on the front.
- For general use, 250–500 mg of EPA + DHA a day matches the authorised claims. Higher doses are for specific purposes and best discussed with a doctor.
- Prefer products with independent testing for oxidation and contaminants (for example IFOS) and a clear best-before date.
- Vegan? Choose algae oil, and check whether it contains EPA as well as DHA.
- Compare the cost per gram of EPA + DHA, not per capsule. Store the pack closed, cool and dark; throw away capsules that smell rancid.
Omega-3 sources and forms compared
| Type | What it is | Good to know |
|---|---|---|
| Fish oil, triglyceride (TG) | Natural form of the oil | Moderate EPA + DHA per capsule |
| Fish oil, ethyl ester (EE) | Concentrated; the fatty acids are bound to ethanol | Cheapest concentrates; take with a meal |
| Re-esterified triglyceride (rTG) | Concentrated, then turned back into TG | High dose per capsule, higher price |
| Krill oil | Omega-3 partly bound to phospholipids | Low EPA + DHA per capsule; expensive per gram |
| Algae oil | From cultivated microalgae | Vegan; often mostly DHA |
What the evidence says
If you eat oily fish (sardines, mackerel, salmon, anchovies) once or twice a week, you probably reach the reference intake already. A supplement makes most sense if you don’t. The authorised claims for heart, brain and vision are based on modest daily amounts of 250 mg; marketing for memory, mood or joints goes beyond them.
Marine oils sold in the UK and the EU must meet limits for dioxins and PCBs. Our fish oil vs algae oil guide compares the two sources and shows how to work out the cost per gram of EPA + DHA.
What the label may legally claim
Authorised claims (GB and EU registers)
- EPA and DHA contribute to the normal function of the heart (250 mg EPA + DHA a day)
- DHA contributes to the maintenance of normal brain function and normal vision (250 mg DHA a day)
- EPA and DHA contribute to the maintenance of normal blood triglyceride levels (2 g a day) and normal blood pressure (3 g a day)
Not authorised in GB or the EU
- Better memory or concentration
- Preventing heart disease
- Joint health
- Better mood
How health claims work (UK & EU): health claims
Products we have checked
Label data checked by NutriMetrics for products sold in Spain and Germany. UK product checks are next. Sorted alphabetically, not ranked.
Who should be careful
- Pregnancy: the NHS advises avoiding fish liver oil (such as cod liver oil) and other vitamin A supplements; omega-3 fish oil is different, but check with your midwife or GP.
- Heart disease: Germany's BfR advises people with existing or impending heart disease to take omega-3 preparations only after consulting a doctor, because of a possible atrial fibrillation risk.
- Blood thinners or surgery: talk to your GP before taking high-dose omega-3.
- Fish or shellfish allergy: check the source; algae oil avoids marine animals.
FAQ
How much omega-3 should I take a day?
If you rarely eat oily fish, a supplement giving 250–500 mg of EPA + DHA a day matches what the authorised claims are based on. EFSA considers up to 5 g a day safe for adults.
Is fish oil or algae oil better?
Both work. Fish oil usually gives more EPA per euro; algae oil is vegan and raised blood DHA as much as fish oil in a comparison trial, but many algae oils contain little EPA.
Is triglyceride (TG) omega-3 better than ethyl ester (EE)?
Re-esterified triglyceride forms may be absorbed somewhat better, especially without food. Taking any form with a meal narrows the gap; the EPA + DHA dose matters more.
Sources
- NHS — Fish and shellfish
- British Dietetic Association — Omega-3 food fact sheet
- NICE NG238 — do not offer omega-3 compounds to prevent CVD (1.12.5)
- DHSC — Great Britain nutrition and health claims (NHC) register
- European Commission — EU Register of nutrition and health claims
- Commission Regulation (EU) No 432/2012 — list of permitted health claims
- EFSA (2012) — Safety of long-chain omega-3 fatty acids (up to 5 g/day EPA + DHA)
- BfR — Omega-3 preparations can increase the risk of atrial fibrillation in heart patients
- Algal-oil supplements are a viable alternative to fish-oil supplements in terms of DHA. Proc Nutr Soc, 2013
- Commission Regulation (EU) 2023/915 — maximum levels for contaminants in food
Information only, not medical advice. No product on this page is a paid placement.