Omega-3 fatty acids are essential polyunsaturated fats that support vital functions throughout the body, from brain and eye health to cardiovascular and inflammatory processes. The three main types—alpha-linolenic acid (ALA), eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA)—each play distinct roles in maintaining cellular structure and regulating inflammation. Whilst ALA is found in plant sources like flaxseeds and walnuts, EPA and DHA are predominantly obtained from oily fish such as salmon, mackerel, and sardines. Understanding what omega-3 is good for can help you make informed dietary choices to support long-term health, whether through food sources or, when appropriate, supplementation under medical guidance.

What Is Omega-3 and Why Does Your Body Need It?

Omega-3 fatty acids are a family of polyunsaturated fats that play crucial structural and functional roles throughout the human body. The three main types are alpha-linolenic acid (ALA), found primarily in plant sources; eicosapentaenoic acid (EPA); and docosahexaenoic acid (DHA), both predominantly found in marine sources. ALA is considered essential because your body cannot synthesise it, while EPA and DHA are conditionally essential as they can be produced from ALA, but in limited amounts.

These fatty acids are integral components of cell membranes throughout the body, particularly in the brain and retina, where DHA constitutes a significant proportion of structural lipids. Omega-3s influence membrane fluidity, which affects how cells communicate and function. Beyond their structural role, EPA and DHA serve as precursors to specialised pro-resolving mediators—bioactive compounds that help regulate inflammatory responses and support the body's natural resolution of inflammation.

The body can convert ALA into EPA and DHA, but this conversion is inefficient, typically around 5-10% for EPA and less than 5% for DHA. This limited conversion capacity means that direct dietary sources of EPA and DHA, particularly from oily fish, are important for maintaining adequate levels. The UK Scientific Advisory Committee on Nutrition (SACN) recommends that adults consume at least two portions of fish per week, one of which should be oily fish. This contributes to a population average intake of approximately 450 mg of EPA and DHA daily, though actual intake varies depending on the species of fish and portion size.

Health Benefits of Omega-3 Fatty Acids

Cardiovascular health represents one of the most extensively researched areas of omega-3 benefit. Evidence from large epidemiological studies suggests that regular consumption of oily fish is associated with reduced risk of cardiovascular events. The mechanisms may include modest reductions in triglyceride levels, slight improvements in blood pressure, and effects on heart rhythm and inflammation. However, it's important to note that NICE does not recommend routine use of over-the-counter omega-3 supplements for cardiovascular disease prevention. For specific high-risk patients already on statins with elevated triglycerides, prescription icosapent ethyl (a purified EPA preparation) may be recommended under NICE guidance (TA805).

Brain and cognitive function benefit significantly from adequate omega-3 intake, particularly DHA, which is highly concentrated in neuronal membranes. During pregnancy and early childhood, DHA is critical for normal brain and visual development. Observational studies suggest associations between higher omega-3 intake and reduced cognitive decline in older adults, though the evidence for supplementation in preventing dementia remains inconclusive. Some research indicates potential benefits in mood disorders, with EPA showing promise in supporting conventional treatment for depression, though omega-3 supplements are not routinely recommended by NICE and should not replace standard psychiatric care.

Anti-inflammatory properties of omega-3 fatty acids may benefit various inflammatory conditions. EPA and DHA compete with omega-6 fatty acids in inflammatory pathways, potentially producing less inflammatory mediators. Some evidence supports benefits in rheumatoid arthritis, with patients reporting reduced joint pain and stiffness, though omega-3s should complement rather than replace disease-modifying treatments. Research into inflammatory bowel disease, asthma, and other inflammatory conditions shows mixed results.

Eye health is supported by DHA's structural role in the retina. Adequate intake during pregnancy and infancy supports visual development, whilst some observational data suggest associations between higher omega-3 consumption and reduced risk of age-related macular degeneration, though supplementation trials have shown inconsistent results.

Best Food Sources of Omega-3 in the UK

Oily fish represents the richest and most bioavailable source of EPA and DHA in the UK diet. Commonly available varieties include salmon (wild and farmed), mackerel, sardines, herring, trout, and fresh tuna. A typical 140g portion of cooked salmon provides approximately 2.5–3g of combined EPA and DHA, well exceeding weekly recommendations in a single serving. Mackerel and herring offer similarly high levels, whilst sardines provide excellent omega-3 content along with calcium from edible bones. It's worth noting that tinned tuna does not count as an oily fish because the canning process reduces the long-chain omega-3 content significantly.

When selecting fish, both fresh and frozen options retain omega-3 content effectively. Tinned oily fish such as sardines, mackerel, and pilchards in oil, brine, or tomato sauce remain excellent sources, offering convenience and affordability. The NHS recommends two portions of fish weekly (one oily), with each portion being approximately 140g cooked weight. However, there are specific consumption limits for certain groups: girls and women who may become pregnant, are pregnant, or are breastfeeding should eat no more than 2 portions of oily fish per week and should avoid shark, swordfish, and marlin due to potential pollutant accumulation. Children, pregnant women and those planning pregnancy should also follow specific NHS guidance on tuna consumption.

Plant-based sources provide ALA, which offers some benefits though conversion to EPA and DHA is limited. Flaxseeds (linseeds) and flaxseed oil are particularly rich in ALA, as are chia seeds, hemp seeds, and walnuts. Rapeseed oil, widely used in UK cooking, contains modest ALA levels. Dark green leafy vegetables like spinach and kale provide small amounts. For those following plant-based diets, algal oil supplements derived from microalgae offer a direct source of DHA, with some products also containing EPA. Check labels for specific EPA and DHA content.

Fortified foods increasingly available in UK supermarkets include omega-3 enriched eggs (from hens fed omega-3 rich diets), certain spreads, yoghurts, and plant-based milk alternatives. Whilst these contribute to overall intake, they typically provide lower amounts than oily fish or dedicated supplements.

Who Should Consider Omega-3 Supplements?

Individuals who do not consume oily fish regularly may benefit from omega-3 supplementation, particularly if dietary intake falls short of recommendations. This includes people with fish allergies, those who dislike fish, or individuals following certain dietary patterns. Vegetarians and vegans face particular challenges obtaining EPA and DHA, as plant sources provide only ALA. For these groups, algal oil supplements offer a suitable alternative, providing direct DHA and sometimes EPA without animal products.

Pregnant and breastfeeding women have increased omega-3 requirements to support foetal and infant brain and visual development. Whilst dietary sources are preferable, supplementation may be appropriate when fish intake is insufficient. However, pregnant women should avoid supplements containing vitamin A (retinol) such as cod liver oil and should choose products specifically formulated for pregnancy, following NHS guidance. Some evidence suggests adequate DHA intake during pregnancy may support gestational length and birth weight, though this is not a blanket recommendation to supplement. Women should discuss omega-3 intake with their midwife or GP and follow NHS fish consumption guidelines.

People with specific medical conditions may require higher omega-3 intakes. Those with hypertriglyceridaemia may be prescribed high-dose omega-3 preparations (typically 2–4g EPA/DHA daily) under medical supervision. For cardiovascular disease, NICE does not recommend routine use of over-the-counter omega-3 supplements for prevention. Prescription icosapent ethyl (a purified EPA preparation) may be offered to specific high-risk patients already on statins with elevated triglycerides under NICE guidance (TA805). Some people with rheumatoid arthritis report symptomatic benefit from omega-3 supplements (typically 2–3g EPA/DHA daily), though this should be discussed with their rheumatology team.

Older adults concerned about cognitive health sometimes consider omega-3 supplements, though evidence for preventing dementia remains inconclusive. Those with limited dietary variety or reduced appetite may have inadequate intake warranting supplementation. Before starting any supplement regimen, individuals should consult their GP or pharmacist, particularly if taking anticoagulant medications (warfarin, DOACs), antiplatelet drugs (aspirin, clopidogrel), or other medications, as omega-3 supplements may increase bleeding risk at high doses. If on warfarin and prescribed high-dose omega-3, additional INR monitoring may be needed when starting or changing dose. People with fish or shellfish allergies should carefully check supplement sources and consider algal alternatives.

Recommended Omega-3 Intake and Safety Guidance

The UK Scientific Advisory Committee on Nutrition (SACN) recommends a population average intake of approximately 450 mg of EPA plus DHA daily. This can be achieved through at least one portion of oily fish weekly, though two portions provide additional benefits. For ALA, adequate intake is considered around 0.2% of dietary energy (approximately 0.5g daily for adults). These recommendations apply to the general population for cardiovascular health maintenance; therapeutic doses for specific conditions may be considerably higher and should only be taken under medical supervision.

Children's requirements vary by age. Infants receive omega-3 through breast milk or formula, with DHA now routinely added to infant formulas in the UK. Young children should be introduced to oily fish from six months, with portions adjusted to age. NHS guidance advises that boys and men can eat up to four portions of oily fish weekly, while girls and women who may become pregnant, are pregnant, or breastfeeding should limit oily fish to two portions weekly. There are also specific NHS guidelines on tuna consumption for children and pregnant women, and certain fish (shark, swordfish, marlin) should be avoided by vulnerable groups due to potential contaminants.

Supplement dosing varies considerably between products. When selecting supplements, it's important to check labels for the specific EPA and DHA content per capsule, not just the total 'fish oil' weight. Standard fish oil supplements typically provide 250–500 mg combined EPA/DHA per capsule, whilst concentrated preparations may provide 1000 mg or more. Cod liver oil, whilst containing omega-3, also contains vitamins A and D; excessive vitamin A intake should be avoided, particularly during pregnancy. Consider products certified by independent testing organisations for purity and absence of contaminants.

Safety considerations are important when using omega-3 supplements. At recommended doses (up to 1g EPA/DHA daily), adverse effects are typically mild, including fishy aftertaste, mild gastrointestinal upset, or loose stools. Taking supplements with meals often reduces these effects. Higher doses (above 3g daily) may increase bleeding risk, particularly in those taking anticoagulants or antiplatelet medications—medical supervision is essential at these levels.

When to contact your GP: Seek medical advice before starting omega-3 supplements if you take anticoagulant or antiplatelet medications, have a bleeding disorder, are scheduled for surgery, or have any concerns about interactions with existing medications. If you experience unusual bruising, prolonged bleeding, or any unexpected symptoms after starting supplements, contact your GP promptly. Report any suspected side effects to the MHRA Yellow Card scheme (yellowcard.mhra.gov.uk). For personalised advice on omega-3 intake, particularly if you have cardiovascular disease, inflammatory conditions, or are pregnant, consult your healthcare provider to ensure recommendations align with your individual health needs.

Frequently Asked Questions