Omega-3 is one of the most widely discussed nutrients for heart, brain and general health. But when you look at fish-oil supplements, the labels can quickly become confusing.
You may see products labelled with 1,000mg, 2,000mg or even 3,000mg of fish oil, while the actual amounts of the important omega-3 fatty acids — EPA and DHA — can be considerably lower.
So how much omega-3 do you actually need? Does taking more provide greater benefits? And should you choose a fish-oil supplement containing both EPA and DHA?
This UK guide explains what omega-3 does, the difference between EPA and DHA, current guidance on intake, potential benefits for heart and brain health, and how to compare omega-3 supplements.
Who this is for (age, lifestyle)
This guide may suit:
UK adults interested in omega-3 for general health
People looking at omega-3 for heart health
Adults interested in the relationship between omega-3 and brain health
People comparing fish-oil supplements
Readers who are unsure about EPA vs DHA
Anyone trying to understand how much omega-3 they need
This content is for general educational purposes only.
What is omega-3?
Omega-3 refers to a family of polyunsaturated fatty acids.
The three most commonly discussed are:
EPA (eicosapentaenoic acid)
DHA (docosahexaenoic acid)
ALA (alpha-linolenic acid)
EPA and DHA are the main long-chain omega-3 fatty acids found in oily fish and fish-oil supplements.
ALA is found mainly in plant foods such as:
Flaxseed
Chia seeds
Walnuts
Rapeseed oil
Soya products
The body can convert some ALA into EPA and DHA, but the conversion is limited. This is one reason oily fish and algae-based sources are important sources of EPA and DHA.
EPA vs DHA: what’s the difference?
Although EPA and DHA are both omega-3 fatty acids, they aren’t identical.
EPA
EPA is particularly associated with normal cardiovascular function and has been extensively studied in relation to cardiovascular health.
DHA
DHA is particularly important in relation to the brain and eyes.
An authorised EU health claim states that DHA contributes to the maintenance of normal brain function and normal vision when consumed at the required intake.
Why both matter
Many fish-oil supplements contain a combination of EPA and DHA.
When comparing products, therefore, don’t focus only on the total amount of fish oil.
Instead, look at:
EPA + DHA per serving
For example:
1,000mg fish oil does not necessarily mean 1,000mg of EPA and DHA.
A product could contain 1,000mg of fish oil but considerably less than 1,000mg of combined EPA and DHA.
Omega-3 and heart health
Heart health is one of the areas where omega-3 has been studied extensively.
EPA and DHA contribute to the normal function of the heart when consumed at an intake of at least 250mg of EPA and DHA per day.
This is an important distinction.
The authorised health claim is about contributing to normal heart function. It should not be interpreted as meaning that taking an omega-3 supplement prevents heart disease or replaces medical treatment.
What about cardiovascular disease?
Research into omega-3 and cardiovascular disease is considerably more complicated than the simple claims often used in supplement marketing.
Benefits observed in specific populations or at specific doses should not automatically be applied to everyone taking an over-the-counter fish-oil supplement.
For people with cardiovascular disease or high triglycerides, treatment decisions should be made with a healthcare professional.
Omega-3 and brain health
DHA is an important structural component of cell membranes, including those found in the brain.
DHA contributes to the maintenance of normal brain function when consumed at the relevant intake.
This has led to considerable interest in omega-3 and:
Cognitive health
Memory
Healthy ageing
Brain structure
Neurological health
However, an important distinction needs to be made.
Maintaining normal brain function is not the same as treating memory problems.
Evidence from studies of omega-3 supplements and cognitive outcomes has been mixed, particularly in people who already have adequate omega-3 intake.
Therefore, it would be misleading to describe fish-oil supplements as a proven treatment for memory loss, dementia or cognitive decline.
For healthy adults, omega-3 should be considered as part of an overall healthy diet rather than a standalone “brain booster”.
Omega-3 and general health
Omega-3 fatty acids have a range of biological functions.
EPA and DHA are incorporated into cell membranes and participate in normal physiological processes throughout the body.
DHA contributes to:
Normal brain function
Normal vision
EPA and DHA contribute to:
Normal heart function
Omega-3 intake is therefore relevant to overall nutrition, but more isn’t automatically better.
A supplement should generally be viewed as a way of filling a dietary gap rather than as a shortcut to better health.
How much omega-3 should you take?
This is one of the most commonly misunderstood aspects of omega-3 supplementation.
For adults, 250mg of combined EPA and DHA per day is a useful reference point from EFSA’s authorised health claims for normal heart function and DHA’s contribution to normal brain function.
However, this shouldn’t be interpreted as a universal prescription for every adult.
Your requirements can depend on:
Overall diet
Oily-fish intake
Age
Individual health circumstances
The reason for supplementation
Other sources of omega-3 in your diet
A simple way to compare supplements
Instead of asking:
“How much fish oil does this capsule contain?”
ask:
“How much EPA + DHA does the serving provide?”
This gives you a much more useful comparison.
How much omega-3 do you get from fish?
For most people, food should remain the starting point.
UK dietary guidance recommends eating at least two portions of fish per week, including one portion of oily fish.
Oily fish includes:
Salmon
Mackerel
Sardines
Pilchards
Herring
Trout
Fish provides EPA and DHA alongside other nutrients.
If you already eat oily fish regularly, you may have less reason to rely heavily on a supplement simply to increase your omega-3 intake.
Which omega-3 supplement should you choose?
There are hundreds of omega-3 products available, and the biggest number on the front of the bottle isn’t necessarily the most important.
Look at EPA
How much EPA does one serving provide?
Look at DHA
How much DHA does one serving provide?
Add EPA + DHA
This gives you the combined amount of the two main long-chain omega-3s.
Check the serving size
A product may advertise a high amount per serving but require several capsules to reach that amount.
Compare cost per serving
A £10 bottle isn’t necessarily better value than a £20 bottle.
Compare:
Price ÷ number of servings
and, if you’re comparing formulations more closely:
Cost per amount of EPA + DHA
Omega-3 dosage: a simple decision guide
If you eat oily fish regularly
You may already be obtaining a meaningful amount of EPA and DHA from your diet.
Focus on maintaining a balanced diet rather than automatically adding a high-strength supplement.
If you rarely eat oily fish
An omega-3 supplement may be a convenient way to increase EPA and DHA intake.
If you want a general-purpose supplement
Look for a product that provides a clearly stated amount of EPA and DHA and compare the serving size and cost.
If you’re considering a high-dose omega-3
Don’t assume that a higher dose is automatically better.
High-dose omega-3 preparations may be used in specific medical circumstances, such as management of very high triglycerides, but these situations should be managed by a healthcare professional.
Omega-3 intake, EPA & DHA and buying options (UK)
| Goal / Situation | EPA + DHA to consider | What to look for | Where to Buy |
|---|---|---|---|
| General health & heart function | 250–500 mg/day | Look for clearly stated EPA + DHA | Amazon UK ↗ |
| Low oily-fish intake | 500–1,000 mg/day | Higher EPA + DHA per serving may be more convenient | Amazon UK ↗ |
| Brain & DHA-focused nutrition | 250–500+ mg/day | Look for a product with a meaningful amount of DHA | Amazon UK ↗ |
| Higher-strength omega-3 | 1,000 mg+ | Compare EPA, DHA and cost per serving rather than fish-oil weight | Amazon UK ↗ |
| Medical/high-dose use | Individualised | Higher doses should be discussed with a healthcare professional | Amazon UK ↗ |
| Vegetarian / vegan option | Depends on product | Choose algae-derived DHA/EPA rather than fish oil | Amazon UK ↗ |
Important
These are comparison ranges, not individual medical prescriptions. For general nutrition, EFSA recognises 250mg of combined EPA + DHA per day in relation to normal heart function. Your dietary intake, oily-fish consumption and individual circumstances should also be considered.
For higher-dose omega-3 supplementation, particularly when being used for a medical condition such as high triglycerides, speak with a healthcare professional.
Pros & cons of omega-3 supplements
Pros
- Convenient source of EPA and DHA
- Useful for people who rarely eat oily fish
- DHA contributes to normal brain function
- EPA and DHA contribute to normal heart function
- Available in a wide range of strengths
- Easy to compare EPA and DHA content between products
Cons
Not everyone needs a high-strength supplement
Fish-oil capsules can cause fishy aftertaste or reflux in some people
Quality varies between products
Total fish-oil weight can be misleading
Supplements don’t provide all the nutritional benefits of eating fish
Higher doses aren’t automatically better
Dosage & safety (UK)
For general nutrition, 250mg of combined EPA and DHA per day is a useful reference point from EFSA’s authorised health claims.
However, supplement dosage should be considered alongside your dietary intake.
Don’t automatically take more
A product providing 1,000mg or more of EPA and DHA isn’t automatically better than one providing 250–500mg for someone simply looking to maintain dietary intake.
Take the manufacturer’s recommended serving
Don’t exceed the recommended dose unless advised by a healthcare professional.
Check other supplements
Some products contain omega-3 alongside other ingredients, including Vitamin D or Vitamin E. Consider your total intake across all supplements.
Medication matters
Speak to your GP or pharmacist before taking higher-dose omega-3 supplements if you:
Take anticoagulant or antiplatelet medication
Have a bleeding disorder
Are preparing for surgery
Have cardiovascular disease
Have very high triglycerides
Take several medications
Are pregnant or breastfeeding
People with a diagnosed cardiovascular condition shouldn’t use an over-the-counter fish-oil supplement as a replacement for prescribed treatment.
What to look for in an omega-3 supplement
When comparing products on Amazon UK, look for:
1. EPA and DHA amounts
These are more useful than the total fish-oil number alone.
2. Serving size
Check whether the advertised amount requires one capsule or several.
3. Source
Look for clear information about the source of the fish oil.
4. Quality testing
Some manufacturers provide information about purity, oxidation and independent testing.
5. Capsule count
A large bottle isn’t necessarily good value if the recommended serving requires multiple capsules.
6. Price per serving
Compare the actual cost of taking the product rather than simply comparing bottle prices.
Browse Omega-3 Supplements on Amazon UK ↗
Frequently Asked Questions
Is omega-3 good for the heart?
EPA and DHA contribute to the normal function of the heart when consumed at the relevant intake. However, omega-3 supplements should not be considered a treatment or cure for cardiovascular disease.
Is omega-3 good for the brain?
DHA contributes to the maintenance of normal brain function. Research into whether omega-3 supplements improve memory or prevent cognitive decline is more mixed, so supplements shouldn’t be marketed as a proven treatment for memory problems.
How much omega-3 should I take per day?
There isn’t one universal supplement dose for everyone. 250mg of combined EPA and DHA per day is a useful reference point from EFSA-authorised health claims, while your dietary intake and individual circumstances also matter.
Is 1,000mg of fish oil the same as 1,000mg of omega-3?
No. A 1,000mg fish-oil supplement may contain considerably less than 1,000mg of EPA and DHA. Always check the individual EPA and DHA amounts on the label.
What is more important, EPA or DHA?
Neither is universally more important. EPA and DHA have overlapping but distinct roles. DHA is particularly relevant to normal brain function and vision, while EPA and DHA contribute to normal heart function.
Should omega-3 be taken in the morning or evening?
There is no established requirement to take omega-3 at a particular time of day. Taking it with a meal may be more comfortable for some people. Follow the product’s directions.
Is omega-3 good for healthy ageing?
Omega-3 contributes to normal physiological functions relevant to health, but it shouldn’t be described as a proven longevity supplement. Maintaining adequate intake as part of an overall healthy lifestyle is a more evidence-based approach.
Final thoughts
Omega-3 is an important part of a healthy diet, particularly because EPA and DHA have established roles in normal health.
DHA contributes to normal brain function, while EPA and DHA contribute to the normal function of the heart at the relevant intake.
For most people, the first step should be looking at their diet. UK guidance recommends eating at least two portions of fish per week, including one portion of oily fish.
If you choose an omega-3 supplement, don’t be distracted by the biggest number on the bottle. A product labelled 1,000mg or 2,000mg fish oil doesn’t necessarily provide that amount of EPA and DHA.
Instead, check:
EPA + DHA + serving size + cost per serving + product quality.
For people looking to compare omega-3 products available in the UK, you can browse the current selection on Amazon:
👉 View Omega-3 Supplements on Amazon UK ↗
