Mon, Oct 05, 26
Omega-3: A Pharmacist’s Guide to EPA, DHA, Omega 3, Fish Oil & Choosing a Supplement
By Lauren O’Reilly, Pharmacist
Omega-3 is one of those supplements that seems to be everywhere, but there is quite a bit of confusion around what you actually need to look for, and who would benefit from supplementing with it.
Fish oil, omega-3, EPA, DHA, algae oil, krill oil – these words aren't all interchangeable, and I’ll break down what they mean in this article. It’s also really important to note that when you're comparing supplements, the biggest number on the front of the packet isn't necessarily the most useful one.
Here’s what I look for when choosing an omega-3 supplement and when supplementation might be worthwhile.
Omega-3 is a family of fatty acids
Omega-3 isn't one single nutrient. There are several omega-3 fatty acids, but the three you'll hear about most are ALA, EPA and DHA.
ALA (alpha-linolenic acid) is found mainly in plant foods such as flaxseed, chia seeds, walnuts and rapeseed oil. Your body can convert ALA into EPA and then DHA, but this conversion is limited. If you specifically want to increase your EPA and DHA intake, eating foods or taking supplements that already contain them is the more practical and effective approach.
EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid) are the long-chain omega-3s found naturally in oily fish and seafood. They're also the forms commonly provided by fish oil and algae-based supplements.
The Role and Benefits of Omega 3s in The Body
Omega-3s have several important roles in the body, but I wouldn't describe an omega-3 supplement as a general cure-all, or something that everybody needs to take.
EPA and DHA contribute to normal heart function, while DHA contributes to the maintenance of normal brain function and normal vision when the relevant intake is achieved. These are authorised EU health claims for omega-3 fatty acids.
There is also good evidence that higher-dose omega-3 preparations can lower triglyceride levels, but this is different from taking a standard over-the-counter omega-3 supplement for general wellbeing. High doses used to manage high triglycerides should be medically supervised.
For most people, I would think about omega-3 as part of a healthy diet first, rather than something everyone automatically needs in supplement form.
When To Supplement Omega 3
Oily fish is an excellent source of EPA and DHA, with salmon, mackerel, sardines, herring and trout among the useful options. The HSE recommends 1 to 2 portions of oily fish a week during pregnancy, for example.
If you regularly eat oily fish, you may already be getting a useful amount of EPA and DHA through your diet.
A supplement may be worth considering if you don't eat oily fish, particularly if you follow a vegetarian or vegan diet. The HSE specifically advises people who are vegetarian or vegan during pregnancy to discuss omega-3 supplementation with their healthcare provider, as EPA and DHA from plant-based foods are limited.
Your overall diet matters too. Omega-3 supplements don't replace the benefits of eating a varied diet containing fish, vegetables, wholegrains, nuts, seeds and other nutrient-rich foods.
Fish oil and omega-3 aren't exactly the same thing
This is one of the most important things to understand when shopping for an omega-3.
Fish oil is the source or oil, whereas EPA and DHA are the omega-3 fatty acids within it.
For example, a capsule might contain 1,000mg of fish oil, but that doesn't mean it provides 1,000mg of EPA and DHA.
A typical fish oil supplement may contain around 180mg EPA and 120mg DHA per 1,000mg of fish oil, although formulations vary considerably.
So when comparing products, don't just look at the big “1,000mg fish oil” number on the front.
Look at the nutrition panel and add together the EPA and DHA.
That's the number I would pay most attention to, and there isn't one universal supplement dose for everyone.
EFSA has established an Adequate Intake of 250mg per day of combined EPA and DHA for adults. During pregnancy and breastfeeding, EFSA recommends an additional 100–200mg of preformed DHA alongside the 250mg EPA+DHA intake.
This doesn't mean everyone needs to take a 250mg supplement every day - it is an intake reference, and dietary sources count too.
When I'm looking at an omega-3 supplement, I'd therefore ask:
How much EPA does it provide? How much DHA? And how much do I get from the recommended daily serving?
Two capsules containing 1,000mg of fish oil aren't necessarily equivalent to two capsules from another brand.
An Omega 3 supplement I often recommend is the Revive Active Omega Active, with a high concentration of EPA and DHA per two capsules.
Vegan omega-3: what is algae oil?
If you don't eat fish, algae oil is the main direct plant-based source of EPA and DHA.
This makes sense when you look at where marine omega-3s originate. EPA and DHA are originally produced by marine microalgae, which then enter the marine food chain and accumulate in fish. Algae oil essentially provides these omega-3s without going through the fish.
Algae supplements can provide DHA, and some provide EPA too, so again, check the label rather than assuming every algae product has the same composition.
The HSE specifically identifies algae supplements as the vegetarian and vegan source of EPA and DHA during pregnancy.
So vegan omega-3 isn't automatically inferior to fish oil. What matters is the actual EPA and DHA content and the quality of the product. The Ancient & Brave True Omegas + contains plant-based sources of Omega 3 and 7.
When is the best time to take omega-3?
There isn't a particular time of day that you need to take omega-3.
I generally recommend taking it with a meal, particularly one containing some fat. Omega-3s are fats, and taking supplements alongside food can also make them easier on the stomach and may reduce the unpleasant “fishy” aftertaste or burps some people experience.
If your supplement recommends a particular serving schedule, follow the product instructions.
Consistency matters much more than whether you take it at breakfast or dinner.
Omega 3 and Medication
This is one area where I would always check before starting a supplement if you're taking regular medication.
Omega-3 supplements can have an antiplatelet effect, particularly at higher doses. There is particular consideration around anticoagulant medicines (some of which are referred to commonly “blood thinners”) as such as warfarin, (and others). While I always recommend speaking to your Pharmacist or GP before starting a new supplement, particularly if you take other medication or have a medical condition, I will highlight here that anyone taking anticoagulants, or with a history of bleeding, should especially discuss omega-3 supplementation with their healthcare professional before starting them, as they may not be suitable, or they need additional monitoring if taking.
High-dose omega-3 is also different from a standard nutritional supplement. Doses around 4g per day are sometimes used medically to lower triglycerides, but these should be only ever be taken under healthcare supervision. Do not exceed the dosage stated on the pack unless medically advised. Some large trials have also found a small increase in atrial fibrillation with 4g/day in people with cardiovascular disease or high cardiovascular risk.
So, if you take blood-thinning medication, have a bleeding disorder, are due to have surgery or are considering a high-dose omega-3 supplement, speak to your GP or pharmacist first.
My pharmacist checklist for choosing an omega-3
When you're standing in front of a shelf of omega-3 supplements, I would look at these five things:
|
What to check |
Why it matters |
|
EPA amount |
One of the main long-chain omega-3s |
|
DHA amount |
Important long-chain omega-3 with authorised health claims |
|
Combined EPA + DHA |
More useful for comparing products than total fish-oil weight |
|
Serving size |
Check how many capsules provide the stated amount |
|
Source |
Fish oil, algae oil, krill oil or another source may suit different diets |
I would also check whether you're buying fish oil or cod liver oil. Cod liver oil contains omega-3 but also naturally provides vitamins A and D, so it shouldn't automatically be treated as interchangeable with a standard fish-oil supplement, and cod liver oil should not be taken in pregnancy or if trying to conceive.
My pharmacist takeaway
If you eat oily fish regularly, you may not need an omega-3 supplement at all.
If you don't eat fish, an omega-3 supplement can be a convenient way of getting EPA and DHA - and algae oil is a useful option if you're vegetarian or vegan.
But don't be distracted by the biggest number on the front of the bottle. When comparing omega-3 supplements, EPA and DHA are the numbers I want you to find on the back of the pack.
And if you're taking medication, particularly anticoagulants, don't assume that because omega-3 is a “natural” supplement it can't interact with your treatment. Check with your pharmacist before starting it.
A note on omega-3: Food should generally be the first source of nutrients. Omega-3 supplements can cause mild side effects such as heartburn, nausea, stomach discomfort or diarrhoea. High-dose supplements are different from standard nutritional doses and should be discussed with a healthcare professional.
