Omega-3 and fish oil are often mentioned together, particularly when talking about heart health, brain function and everyday nutrition. You might even see the terms used interchangeably on supplement packaging.
But are they actually the same thing?
The short answer is no. Omega-3 refers to a family of essential fatty acids, while fish oil is one source of these fats. Understanding the difference can help you make sense of supplement labels, compare products and choose an option that suits your diet.
Here's what you need to know about omega-3, fish oil and the different types available.
What Is Omega-3?
Omega-3 is a type of polyunsaturated fatty acid (often called a healthy fat) that plays several important roles in the body.
There are three main types of omega-3:
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ALA (alpha-linolenic acid): Mainly found in plant foods such as flaxseed, chia seeds, walnuts and rapeseed oil.
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EPA (eicosapentaenoic acid): Found mainly in oily fish and seafood.
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DHA (docosahexaenoic acid): Also found mainly in oily fish and seafood, and an important component of the brain and retina. ¹
ALA is known as an essential fatty acid because the body cannot produce it, meaning we need to get it from our diet. The body can convert ALA into EPA and DHA, but this process is limited. If you want to increase your intake of EPA and DHA specifically, oily fish or a suitable supplement can provide a more direct source. ¹
What Is Fish Oil?
Fish oil is an oil extracted from the tissues of oily fish. It's naturally rich in two long-chain omega-3 fatty acids: EPA and DHA.
Common sources include:
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Anchovies
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Sardines
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Mackerel
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Salmon
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Herring
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Tuna
Fish oil is widely available as a dietary supplement, usually in softgel capsules or liquid form. The amount of omega-3 it contains varies depending on the fish oil used and how concentrated the product is. ²
It's important to remember that fish oil and omega-3 aren't interchangeable terms. Fish oil contains omega-3, but omega-3 can also come from other sources, including plant foods and algae.
Omega-3 vs Fish Oil: What's the Difference?
The easiest way to understand the difference is to think of omega-3 as the nutrient and fish oil as one way of getting it.
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Omega-3 |
Fish oil |
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A family of essential fatty acids |
An oil extracted from fish |
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Includes ALA, EPA and DHA |
Mainly provides EPA and DHA |
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Found in fish, algae, nuts, seeds and plant oils |
Naturally sourced from oily fish |
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Available in fish, algae and plant-based supplements |
Available as capsules or liquid |
So, when you see a supplement labelled as fish oil, you're looking at the source. When you see omega-3, you're looking at the fatty acids it provides.
What Are EPA and DHA, and Why Do They Matter?
EPA and DHA are two of the most widely researched omega-3 fatty acids. Although they're often grouped together, they have slightly different roles in the body.
EPA (Eicosapentaenoic Acid)
EPA is involved in several important processes, including the production of signalling molecules that help regulate normal bodily functions.
It's often discussed alongside DHA in research into cardiovascular health and the role of omega-3 in the body.
DHA (Docosahexaenoic Acid)
DHA is an important structural component of cell membranes, particularly in the brain and retina of the eye.
It contributes to the maintenance of normal brain function and normal vision. ²
EPA and DHA Together
EPA and DHA are often combined in fish oil supplements because they provide complementary omega-3 fatty acids.
Both contribute to normal heart function when consumed at a combined daily intake of 250mg. ²
This is an authorised nutrition and health claim, but it's worth remembering that taking an omega-3 supplement isn't a guaranteed way to prevent heart disease or replace medical treatment.
What Are the Benefits of Omega-3?
Omega-3 fatty acids are important for several aspects of normal health and wellbeing.
Here are some of the key roles associated with EPA and DHA.
Heart Health
EPA and DHA contribute to the normal function of the heart when consumed at a combined daily intake of 250mg. ²
Oily fish is a useful dietary source, and the NHS recommends eating at least two portions of fish a week, including one portion of oily fish. ³
Brain Function
DHA contributes to the maintenance of normal brain function. ²
It's a key structural component of the brain, which is why it's an important nutrient to include as part of a balanced diet.
Normal Vision
DHA also contributes to the maintenance of normal vision. ²
Like the brain, the retina contains high concentrations of DHA, making it an important part of normal eye function.
Pregnancy and Early Development
DHA is particularly important during pregnancy because it contributes to the normal development of the brain and eyes of the foetus and breastfed infants. ²
Pregnant women should follow NHS advice on oily fish consumption and avoid fish liver oil supplements, such as cod liver oil, unless advised otherwise by a healthcare professional.
Fish Oil vs Omega-3 Supplements: What Should You Look For?
If you're considering an omega-3 supplement, one of the most important things to check is how much EPA and DHA it actually provides. This is where supplement labels can become confusing, for example, a product might advertise 2000mg of fish oil, but that doesn't mean it contains 2000mg of omega-3. Some of that total weight comes from other fatty acids.
Look for the individual EPA and DHA amounts on the label rather than relying on the overall fish oil figure.
A few other things are worth considering:
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EPA and DHA content: Check how much of each fatty acid is provided per serving.
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Serving size: Compare the amounts per daily serving, not just per capsule.
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Source: Look for information about where the fish oil comes from.
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Quality and testing: Independent testing can provide additional information about product quality and checks for contaminants.
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Capsule ingredients: Check the ingredients if you have dietary requirements or allergies.
For example, Zipvit's Super Strength Omega 3 Fish Oil 2000mg provides 660mg EPA and 440mg DHA per daily serving, giving 1100mg of omega-3 in total.
That distinction between the total fish oil amount and the actual omega-3 content is important when comparing supplements.
What About Plant-Based Omega-3?
You don't have to eat fish to get omega-3. There are several plant-based foods that provide ALA, including:
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Chia seeds
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Flaxseeds and flaxseed oil
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Walnuts
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Rapeseed oil
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Soya beans
These are useful additions to a balanced diet, but remember that ALA is different from EPA and DHA. The body converts only a small proportion of ALA into these longer-chain omega-3s. ¹
If you follow a vegetarian or vegan diet and want a direct source of DHA, algae-based supplements are another option. Algal oil is a plant-based source of DHA, and some products also provide EPA. ¹
Is Fish Oil the Same as Cod Liver Oil?
Not quite. Both are fish-derived oils and can provide EPA and DHA, but they come from different parts of the fish. Fish oil is extracted from the body tissues of oily fish and is primarily used as a source of omega-3 fatty acids.
Cod liver oil is extracted from the liver of cod and naturally contains vitamins A and D alongside omega-3. This difference matters because taking too much vitamin A or vitamin D can be harmful. Cod liver oil isn't automatically a better choice simply because it contains additional vitamins. ²
If you're pregnant, trying to conceive or taking other vitamin supplements, check the ingredients carefully and follow NHS advice before using cod liver oil.
Should You Take an Omega-3 Supplement?
For many people, the best starting point is to include omega-3-rich foods in their diet. The NHS recommends eating at least two portions of fish a week, one of which should be oily fish. A portion is around 140g. ³
If you don't eat fish, or you struggle to include oily fish regularly, a supplement may be a convenient way to increase your intake of EPA and DHA. Algal oil is an alternative for those following a plant-based diet.
However, supplements aren't essential for everyone. Research into the benefits of omega-3 supplements for preventing cardiovascular disease is mixed, and they shouldn't be treated as a replacement for a balanced diet or prescribed medication. ⁴
If you take medication that affects blood clotting, have a medical condition or are considering higher-dose omega-3 supplements, speak to your GP or pharmacist first. ⁴
FAQs
Is omega-3 better than fish oil?
They're not really competing options. Omega-3 is the nutrient, while fish oil is one source of it. Fish oil is a convenient way to get EPA and DHA, but omega-3 can also come from foods and supplements made using algae or plant oils.
How much omega-3 should I take each day?
There isn't one universal supplement dose for everyone. However, the authorised EU health claim for normal heart function applies to a combined daily intake of 250mg EPA and DHA. ² This isn't a recommendation that everyone needs to take a supplement providing that amount.
Does fish oil contain EPA and DHA?
Yes. Fish oil naturally contains both EPA and DHA, although the amounts vary between products. Always check the supplement label to see how much each capsule or daily serving provides.
Can I get omega-3 without eating fish?
Yes. Foods such as walnuts, chia seeds and flaxseeds provide ALA, while algal oil supplements can provide DHA and sometimes EPA. ¹
Is fish oil the same as cod liver oil?
No. Fish oil is extracted from fish tissue, while cod liver oil comes from the liver of cod. Both can provide EPA and DHA, but cod liver oil also contains vitamins A and D.
Can I take omega-3 every day?
Many people take omega-3 supplements daily, but whether you need one depends on your diet and individual circumstances. Follow the product's recommended serving and speak to a healthcare professional if you take medication or have concerns about suitability.
Omega-3 and fish oil are closely related, but they're not the same thing. Omega-3 is a family of fatty acids, while fish oil is one of the most common sources of EPA and DHA.
When choosing a supplement, don't just look at the total amount of fish oil. Check how much EPA and DHA you're actually getting, along with the serving size and product quality.
Whether you get your omega-3 from oily fish, plant foods or a supplement, understanding the difference can help you make a more informed choice about your everyday nutrition.
