Wellness · Nutrition
Omega-3, food, supplements, and what the evidence really shows.
EPA and DHA — the two omega-3s that matter — are consistently linked to cardiovascular and cognitive health. Here is how to get them, and when a supplement is worth it.
Why trust this guide
- 01
Clinically reviewed
Written by our editorial team and reviewed by a registered UK clinician before publication.
- 02
Sourced from the trials
Grounded in NICE guidance, Cochrane reviews and SACN advice — not supplement marketing.
- 03
Practical, not preachy
Built for a UK kitchen with a normal budget, freezer and shopping habits.
Key facts
Omega-3 at a glance.
The essentials, in plain English — what omega-3 is, what the evidence shows, and how to actually get it.
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The three omega-3s
ALA (plants), EPA and DHA (marine). EPA and DHA do the heavy lifting.
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Food sources
Oily fish two times a week is the reference intake — salmon, mackerel, sardines.
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Plant sources
Walnuts, flax and chia give ALA — but conversion to EPA/DHA is poor.
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When a supplement helps
Limited oily fish, plant-based diets and pregnancy are the common cases.
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Dose
250–500 mg combined EPA+DHA daily for general maintenance.
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Fish oil vs algae oil
Both deliver EPA/DHA. Algae oil is the vegan option and typically DHA-rich.
Why this guide matters
One nutrient, a lot of marketing.
Fish-oil aisles are noisy. The evidence is quieter and clearer — the three points below shape everything else on this page.
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EPA and DHA are the actives
Total fish oil on a label doesn’t matter — the EPA and DHA content does.
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Food beats capsules
Two portions of oily fish a week hits the target. Supplements fill a gap.
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Dose is a decision
250–500 mg a day is maintenance. Higher doses are clinical, not lifestyle.
The evidence in practice
From food to supplement — step by step.
The order most people find easiest to adopt — food first, capsule second, dose last.
Phase 1 · Food
Oily fish twice weekly
Phase 2 · Supplement
Choose EPA+DHA, check purity
Phase 3 · Dose
Only high with medical advice
- 01
Food
Aim for 2 portions of oily fish weekly
Salmon, mackerel, sardines, trout or herring.
- 02
Food
If you don’t eat fish, take a supplement
Fish oil or algae oil closes the gap reliably.
- 03
Food
Choose EPA+DHA content on the label
Not total fish oil — the actives are EPA and DHA.
- 04
Supplement
Look for third-party purity testing
IFOS, GOED or USP marks — checks for oxidation and heavy metals.
- 05
Supplement
Consider algae oil if vegan or pregnant
A direct DHA source without fish-derived contaminants.
- 06
Dose
Higher doses only under medical advice
Above 1 g EPA+DHA/day is a clinical decision.
- 07
Dose
Check with a doctor if on anticoagulants
Warfarin and DOACs interact — don’t self-prescribe high doses.
Typical timeline: 2–4 weeks to establish a routine and notice tolerance.
Where it helps
What omega-3 actually does — and where the evidence sits.
Eight places EPA and DHA earn their keep — from cardiovascular support to pregnancy — with one red flag to check.
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Cardiovascular support
Modest benefit on triglycerides and rhythm; part of a wider heart-healthy pattern.
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Brain and mood support
DHA is a structural fat in the brain; modest signal for mood in some trials.
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Eye health (DHA)
DHA is concentrated in the retina — important through pregnancy and infancy.
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Pregnancy (DHA for baby)
DHA supports fetal brain and eye development — dedicated antenatal supplements exist.
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Skin inflammation
May help eczema and psoriasis flares as an adjunct — not a replacement for treatment.
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Chronic inflammation (rheumatoid)
Adjunct evidence in rheumatoid arthritis — discuss dose with your rheumatologist.
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Raised triglycerides
Higher-dose EPA formulations have specific evidence — a specialist decision.
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Red flag: anticoagulation
On warfarin or a DOAC? Talk to your GP before starting high doses.
How to do it
Practical ways to hit your omega-3 target.
Not a shopping list, not a meal plan — eight practical routes to a steady EPA+DHA intake.
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2 portions oily fish weekly
The simplest, most evidence-based route — salmon, mackerel, sardines, trout.
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Fish-oil capsule 250–500 mg EPA+DHA
A pragmatic gap-filler when fish isn’t on the menu twice a week.
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Algae oil (vegan)
Direct DHA (often with EPA) from micro-algae — no fish involved.
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Higher-dose EPA for triglycerides
Prescription-grade EPA is a specialist choice, not a supermarket buy.
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Pregnancy DHA supplement
A dedicated antenatal DHA product is the cleanest way to hit the target.
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Store in the fridge
Cold storage slows oxidation — rancid oil is worse than no oil.
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Split dose with meals
Taking with food reduces reflux and improves absorption.
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Third-party purity tested product
IFOS, GOED or USP marks tell you it has been independently checked.
What this guide is based on
The evidence behind every claim on this page.
Systematic reviews, national guidance and UK public-health advice — current at the time of last review.
Key references
The reviews and guidance we relied on.
A quiet reminder
This guide is for information, not medical advice.
A GP, pharmacist or registered dietitian can tell you whether — and how — a supplement fits your health.
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British Heart Foundation — omega-3 guidance for the public.
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National Institute for Health and Care Excellence (NICE). Cardiovascular disease prevention NG238.
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Cochrane review — omega-3 fatty acids for the primary and secondary prevention of cardiovascular disease.
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Scientific Advisory Committee on Nutrition (SACN) — advice on oily fish consumption.
Red flags
When to get medical advice before starting or increasing omega-3.
Omega-3 is safe for most people at maintenance doses. These are the situations where a clinician, not a supplement aisle, is the right next step.
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High-dose fish oil on warfarin/DOAC
Bleeding risk rises — dose decisions belong with your GP.
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Bariatric fat malabsorption
Absorption is unpredictable after some bariatric surgeries — specialist input.
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Very high triglyceride states
Pancreatitis risk — this is a lipid clinic conversation, not a supplement one.
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Allergy to fish
Use algae oil instead of fish-derived products.
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Pregnancy — mercury-safe sources
Avoid shark, swordfish and marlin; limit tuna; DHA-only antenatal products are safest.
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Immunosuppression
Higher doses may modulate immunity — discuss with your specialist.
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Chronic diarrhoea from high doses
A common sign the dose is too high — step it down.
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Rancid supplements
Fishy burps, oxidised smell — discard and choose a fresher, tested product.
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Children — dose by weight
Adult doses aren’t appropriate for young children — ask your GP or pharmacist.
Making it stick
A habit for years, not a bottle for weeks.
Four ideas that decide whether omega-3 becomes a real part of your week, or a jar at the back of the cupboard.
A quiet reminder
Consistency beats intensity, every time.
A steady intake most weeks does far more than a mega-dose you take once and forget.
- 01 Pattern
Food first, supplement second
Two portions of oily fish a week beats any capsule — the supplement fills a gap it doesn’t replace one.
- 02 Quality
Freshness matters more than brand
Cold storage, sealed packaging and third-party testing keep the oil doing its job.
- 03 Dose
More is not better
Above 1 g EPA+DHA/day is a clinical decision — bleeding and GI side-effects rise.
- 04 Flexibility
A weekly target, not a daily rule
Miss a day, catch up over the week — the biology cares about the average.
Frequently asked
Everything we get asked about omega-3.
Quick answers on dose, fish vs algae, cod liver oil, pregnancy and blood thinners.
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Do I need a supplement if I eat oily fish twice a week?
Usually no — two portions of oily fish a week hits the target intake.
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Fish oil or algae oil?
Both work. Algae oil is the vegan option and avoids fish-derived contaminants.
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What dose should I take?
250–500 mg combined EPA+DHA daily for general maintenance. Higher doses are a clinical decision.
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Is cod liver oil the same?
It contains omega-3 but also vitamins A and D — read the label, and don’t stack it with other vitamin-A products.
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Can I take it in pregnancy?
Yes — a dedicated antenatal DHA supplement is the cleanest option. Avoid high-mercury fish.
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Does it interact with blood thinners?
It can. Talk to your GP before starting, especially at higher doses.
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