What Does Omega-3 Do for the Body? EPA, DHA and the Systems they Support

Do you eat fish twice a week? Go on and admit it, we bet you don’t. But by the end of this article, we think you will be vowing to eat it more often!

If you've ever asked what does omega-3 do for the body, the short answer is: quite a lot, and in more than one way. Omega-3s are a family of fats that your body needs but can't make on its own, which is why they're called "essential." They get built into cell membranes, they're a raw material for signalling molecules that help control inflammation, and two of them - EPA and DHA - turn up in unusually high concentrations in the heart, brain and eyes.

So what is omega-3 good for, specifically? Rather than one blanket benefit, omega-3s support several systems at once: cardiovascular health, brain function, eye health, joint comfort and skin condition, among others. Two of the three main omega-3 fats, EPA and DHA, do most of the heavy lifting, and they don't do quite the same job.

Understanding that EPA/DHA split is the fastest way to understand everything else in this article, so that's where we'll start before working through the body system by system.

At a Glance: What Omega-3 Does

Researchers are still uncovering all the health benefits of Omega 3s, and this is of course true of all nutrients. As our knowledge grows, the strength of evidence behind each health benefit varies. 

This table summarises the health benefits that are conclusively proven. They are health claims authorised by EFSA (The European Food Safety Authority) whose scientists examine all research rigorously before authorising each claim. 

The EFSA authorised claims for EPA and DHA

Key facts

• Structural fat: DHA is a major building block of brain and retina cell membranes, supporting normal brain and eye function.

• Inflammation control: EPA is a precursor to signalling molecules (eicosanoids) that help regulate the body's inflammatory response.

• Heart support: Omega-3s are linked to healthy triglyceride levels and normal blood pressure as part of a balanced diet.

• Joints, skin and mood: Emerging but genuine evidence supports omega-3 for joint comfort, skin hydration, and mood balance.

EPA vs DHA: What's the Difference?

Fish oil supplements almost always list two numbers on the label: EPA and DHA. They're both omega-3s, and they overlap in what they do, but each one has a primary role.

There's a third omega-3 worth knowing: ALA (alpha-linolenic acid), found in plant sources like flaxseed, chia and walnuts. The catch is that the body converts ALA into EPA and DHA very inefficiently - typically only a small fraction gets converted - so ALA-rich foods alone usually aren't enough to match what oily fish or a fish oil supplement provides.

You may also see products marketed as omega-3-6-9. Omega-6 and omega-9 are separate fat families, and most people eating a typical Western diet already get plenty of omega-6 and omega-9 from vegetable oils and everyday foods. Omega-3 is the one that's usually under-supplied, which is why it tends to get most of the attention - and most of this article.

For guidance on exactly how much to take, see our full breakdown of how much omega-3 per day you actually need, since the right amount depends on your goals and diet.

Omega-3 for the Heart

Did you know around 12% of your brain is made up of DHA? More specifically, DHA (docosahexaenoic acid) accounts for around 10–20% of the brain's total fatty acids, with an average often quoted at around 12%. It is particularly concentrated in the grey matter, where it forms part of the membranes surrounding brain cells. These membranes aren't simply protective barriers; they help neurons communicate efficiently, allowing signals to pass rapidly throughout the brain.

Because DHA is a major structural component of brain tissue, it is considered essential for normal brain function throughout life. It helps maintain the flexibility and integrity of nerve cell membranes, supporting healthy communication between brain cells. This is why DHA is especially important during pregnancy and early childhood, when the brain is developing rapidly and demand for this omega-3 fatty acid is at its highest.

DHA continues to play an important role during adulthood. Although the brain's structure is largely established, brain cells are constantly repairing and renewing their membranes. Maintaining adequate DHA intake helps support these normal processes and contributes to healthy cognitive function as we age.

EPA supports brain health in a different way. Rather than forming part of brain tissue itself, EPA is involved in producing signalling molecules that help regulate inflammation throughout the body, including within the nervous system.

Researchers have also investigated EPA's role in supporting mood and emotional wellbeing, with several studies suggesting it may be beneficial for some people, particularly when combined with medical treatment where appropriate.

Together, DHA and EPA provide complementary benefits for brain health. DHA provides the structural foundation that allows brain cells to function normally, while EPA supports the biological processes that help maintain a healthy environment for those cells to communicate effectively.

Key facts

DHA is one of the brain's most important structural fats, making up around 12% of its fatty acids. It helps maintain healthy brain cell membranes and supports normal cognitive function, while EPA helps regulate inflammatory processes that contribute to overall brain health. 

Omega-3 for the Eyes

Your eyes contain one of the highest concentrations of DHA anywhere in the body. In fact, DHA is the predominant omega-3 fatty acid in the retina – the light-sensitive layer of tissue at the back of the eye that converts light into signals the brain can interpret. This makes DHA essential for maintaining the normal structure and function of the retina throughout life.

The retina is made up of millions of specialised photoreceptor cells that rely on flexible, healthy cell membranes to function properly. DHA is a key component of these membranes, helping them remain fluid and responsive so visual signals can be transmitted efficiently. Without adequate DHA, the retina cannot function as effectively, highlighting why omega-3 is considered an important nutrient for normal vision.

Omega-3 is particularly important during pregnancy and infancy, when the eyes and visual system are developing rapidly. During this time, DHA accumulates in the retina and brain, supporting healthy visual development. This is one reason why DHA is commonly included in infant formula and why adequate omega-3 intake is recommended during pregnancy and breastfeeding.

In adults, omega-3 continues to support normal eye health. Research suggests that people with higher intakes of omega-3 are more likely to maintain healthy vision as they age. EPA and DHA have also been studied for their role in supporting tear production and maintaining a healthy ocular surface, making omega-3 a popular supplement for people experiencing dry, irritated eyes.

Because the body cannot produce significant amounts of DHA on its own, regular intake through oily fish or a high-quality omega-3 supplement is the most reliable way to maintain healthy levels. This helps ensure the retina has the structural building blocks it needs to continue functioning normally throughout life.

Key facts

DHA is the primary omega-3 fatty acid found in the retina, where it helps maintain the structure of photoreceptor cells and supports normal vision. Together, EPA and DHA also contribute to healthy tear production and long-term eye health.

Omega-3 for Joints

Joint comfort is one of the more intuitive omega-3 benefits, because it follows directly from EPA's role in inflammation. Since eicosanoids derived from EPA help regulate the body's inflammatory pathways, adequate omega-3 intake is thought to support a more balanced inflammatory response in and around the joints.

Is omega-3 good for joints specifically, then? The evidence is modest but real - several studies, particularly in people with rheumatoid arthritis, have found that omega-3 supplementation is associated with reduced joint stiffness and tenderness, and some research has noted a reduced need for anti-inflammatory medication in participants taking omega-3 alongside their usual treatment. For general, everyday joint stiffness that isn't linked to a diagnosed inflammatory condition, the evidence is thinner but still points in a broadly similar, anti-inflammatory direction.

It's not a replacement for medical treatment, but it's a reasonable, evidence-supported addition for people managing everyday joint stiffness or looking to support long-term joint comfort. Omega-3 is also commonly paired with glucosamine and chondroitin for joint support, since the three nutrients work on joint health from different angles - you can read more in our article on combining glucosamine, chondroitin and omega-3.

Omega-3 for Skin and Hair

Cell membranes aren't just relevant to the brain and eyes. They're relevant everywhere, including the skin. Omega-3s are thought to support the skin's barrier function, which affects hydration and how well skin retains moisture. There's also research interest in omega-3's role in supporting skin comfort in inflammatory skin conditions, again tying back to EPA's effect on inflammatory signalling.

Omega-3 benefits for skin are generally framed around barrier support and hydration rather than dramatic cosmetic change, and that's the honest picture. A well-functioning skin barrier helps the skin retain water and resist irritants, and some research suggests omega-3 intake is associated with improvements in skin hydration and a reduction in transepidermal water loss - the technical term for how much moisture escapes through the skin's surface.

For hair, the evidence is thinner, but omega-3's role in supporting cell membrane health and reducing inflammation is thought to extend to hair follicles as well, since follicles are metabolically active tissue with their own blood supply and nutrient demands. This is why omega-3 is sometimes included in hair health formulations alongside biotin and other nutrients, even though it's rarely the headline ingredient.

Omega-3 Benefits for Women and Men

Omega-3's core benefits - cardiovascular, brain, eye, joint and skin support - apply to everyone, but there are some differences worth flagging.

Omega-3 benefits for women get particular attention around pregnancy, since DHA is important for foetal brain and eye development, and needs typically increase during pregnancy and breastfeeding. If that applies to you, dosing is genuinely worth getting right - our how much omega-3 per day guide covers pregnancy-specific amounts in more detail.

Omega-3 benefits for men tend to centre more on the cardiovascular and joint angles covered above, particularly for men managing cholesterol, blood pressure or joint stiffness. In practice, the differences between the sexes are more about life stage and individual health priorities than about fundamentally different mechanisms. The underlying biology of EPA and DHA is the same either way.

How to Get Enough Omega-3

The most direct source of EPA and DHA is oily fish, and that doesn’t mean deep fried cod from the chippie! Oily fish includes salmon, mackerel, sardines and anchovies; essentially, any fish whose flesh is beige or pink rather than white. You can also get fairly good amounts of Omega 3s from prawns, mussels and other seafood. White fish like cod contains far less of these essential oils. 

For anyone eating fish once or twice a week, dietary intake alone may go a reasonable distance, though most people in modern Britain fall short of that.

For vegans and vegetarians, algae-based supplements are the only direct source of EPA and DHA that doesn't involve fish, since algae is actually where fish get their omega-3s in the first place. Plant sources like flaxseed and walnuts provide ALA, which is useful but, as covered above, converts to EPA and DHA poorly.

For most people who don't eat oily fish regularly, a fish oil supplement is the simplest way to close the gap. If you're looking for a more concentrated option, a high-strength omega 3 supplement is worth considering, since it delivers a meaningful dose of EPA and DHA in fewer capsules than standard-strength alternatives. 

For exact amounts by age, goal and life stage, our how much omega-3 per day guide has the detail. It’s important to know that you must never go over a combined daily intake of 5 grams of EPA and DHA.

Conclusion

So, did we make you vow to eat more oily fish?

Omega-3 isn't a single-benefit nutrient - it's a family of fats that supports several systems at once, from the heart to the brain, eyes, joints and skin. EPA leans toward inflammation regulation and cardiovascular signalling, while DHA is more structural, showing up heavily in the brain and retina. Which one matters most to you may depend on what you're trying to support, but consistent intake at a genuinely effective dose is what makes the difference either way.

If you just hate fish, or worry that you're not getting EPA and DHA from food alone, a high-quality omega 3 supplement is a straightforward way to close the gap. Our guide to how much omega-3 you need per day can help you land on the right amount for your needs.

Research Sources

1. Heart / Cardiovascular

Effect of omega-3 fatty acids on cardiovascular outcomes: A systematic review and meta-analysis, Khan SU, Lone AN, Khan MS, Virani SS, Blumenthal RS, Nasir K, Miller M, Michos ED, Ballantyne CM, Boden WE, Bhatt DL, eClinicalMedicine (Lancet Discovery Science), 2021, Vol. 38, 100997
https://www.thelancet.com/journals/eclinm/article/PIIS2589-5370(21)00277-7/fulltext

2. Brain / Cognitive Function

A systematic review and dose-response meta-analysis of omega-3 supplementation on cognitive function, Scientific Reports, 2025
https://www.nature.com/articles/s41598-025-16129-8 (also available via PMC: https://pmc.ncbi.nlm.nih.gov/articles/PMC12368174/)

3. Eyes / Dry Eye Disease

Efficacy of Omega-3 Intake in Managing Dry Eye Disease: A Systematic Review and Meta-Analysis of Randomized Controlled Trials, Wang WX, Ko ML, Journal of Clinical Medicine, 2023, 12(22):7026
https://pmc.ncbi.nlm.nih.gov/articles/PMC10672334/

4. Joints / Rheumatoid Arthritis

Evaluation of the Clinical Outcomes Associated With the Use of Fatty Acids and Vitamin D in Rheumatoid Arthritis Patients: A Systematic Review and Meta-Analysis (reviews 14 fatty-acid Randomised Controlled Trials in RA patients), (PMC open-access journal), 2024/2025
https://pmc.ncbi.nlm.nih.gov/articles/PMC12278022/

5. Skin

Therapeutic Benefits of Topical Omega-3 Polyunsaturated Fatty Acids in Skin Diseases and Cosmetics: An Updated Systematic Review, (PMC open-access journal), 2024/2025
https://pmc.ncbi.nlm.nih.gov/articles/PMC12228025/