Omega-3 fatty acids are essential polyunsaturated fats that play vital roles in cardiovascular health, brain function, and inflammation regulation. Whilst the UK has no official Reference Nutrient Intake for omega-3s, the NHS recommends consuming at least two portions of fish weekly, including one oily fish portion such as salmon or mackerel. This typically provides approximately 250–300mg of combined EPA and DHA daily. Understanding how much omega-3 fatty acids per day you need depends on your age, life stage, and individual health circumstances. This article explores evidence-based recommendations for omega-3 intake across different populations, food sources versus supplements, and important safety considerations.

Recommended Daily Intake of Omega-3 Fatty Acids in the UK

In the United Kingdom, there is currently no official Reference Nutrient Intake (RNI) specifically for omega-3 fatty acids established by the Scientific Advisory Committee on Nutrition (SACN). However, the NHS and various health organisations provide guidance based on international evidence and expert consensus.

The general recommendation for adults is to consume at least two portions of fish per week, with one portion being oily fish such as salmon, mackerel, or sardines. A standard portion of oily fish (approximately 140g) typically provides about 1-2g of the long-chain omega-3 fatty acids eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), depending on the species. This equates to roughly 250-300mg of combined EPA and DHA per day when averaged across the week, which aligns with the European Food Safety Authority (EFSA) adequate intake recommendation of 250mg daily for cardiovascular health.

For individuals who do not consume fish, plant-based sources of alpha-linolenic acid (ALA) are important. EFSA suggests an adequate intake of approximately 0.5% of daily energy intake from ALA, which equates to roughly 1-2g daily for most adults. ALA can be converted to EPA and DHA in the body, though this conversion is relatively inefficient (typically less than 10%).

It is important to note that these recommendations represent minimum targets for general health maintenance. Specific clinical conditions may warrant different intakes under medical supervision. Higher amounts (2-4g daily) are sometimes prescribed for severe hypertriglyceridaemia, though such doses should only be taken following consultation with a healthcare professional.

Different Types of Omega-3: EPA, DHA and ALA

Omega-3 fatty acids comprise a family of polyunsaturated fatty acids with distinct chemical structures and biological functions. Understanding the differences between the three main types—EPA, DHA, and ALA—is essential for making informed dietary choices.

Eicosapentaenoic acid (EPA) is a long-chain omega-3 fatty acid containing 20 carbon atoms. It serves as a precursor for eicosanoids, which are signalling molecules involved in regulating inflammation, immune function, and platelet aggregation. EPA has been particularly studied for its potential cardiovascular benefits and anti-inflammatory properties. Clinical evidence suggests EPA may help reduce triglyceride levels and may have a role in managing certain inflammatory conditions, though individual responses vary.

Docosahexaenoic acid (DHA) is a 22-carbon long-chain omega-3 fatty acid that is a major structural component of neuronal cell membranes, particularly in the brain and retina. DHA is crucial for normal brain development during pregnancy and infancy, and maintains cognitive function throughout life. Research indicates DHA is highly concentrated in brain and retinal tissues, where it plays important roles in neural and visual function. DHA is particularly important during pregnancy, lactation, and early childhood.

Alpha-linolenic acid (ALA) is an 18-carbon essential fatty acid, meaning the body cannot synthesise it and must obtain it from dietary sources. ALA is found primarily in plant-based foods and serves as a precursor for EPA and DHA synthesis. However, the conversion efficiency is limited—typically only 5-10% of ALA is converted to EPA, and less than 1% to DHA. This conversion can be further reduced by high intakes of omega-6 fatty acids (common in Western diets), certain genetic variations, and nutritional deficiencies in vitamins and minerals required for the conversion enzymes.

Omega-3 Requirements for Different Age Groups and Life Stages

Omega-3 requirements vary considerably across the lifespan, reflecting changing physiological needs during growth, development, and ageing.

Pregnancy and lactation represent periods of particularly high omega-3 demand. DHA is essential for foetal brain and eye development, especially during the third trimester when rapid neurological growth occurs. The NHS recommends pregnant and breastfeeding women consume two portions of fish weekly (including one oily fish portion), whilst limiting oily fish to two portions due to potential pollutant concerns. Women should avoid certain fish high in mercury (shark, swordfish, marlin) and should limit tuna to no more than two fresh tuna steaks or four medium-sized cans per week. Importantly, pregnant women should avoid cod liver oil supplements due to their high vitamin A (retinol) content, which may harm the developing baby. If fish consumption is inadequate, supplementation with 200-300mg DHA daily may be considered, though women should consult their midwife or GP before starting supplements.

Infants and children require adequate DHA for ongoing brain development and visual function. Breast milk naturally contains DHA (amounts vary with maternal diet), and infant formulas in the UK are now routinely fortified with DHA. For children consuming solid foods, the recommendation is one to two portions of fish weekly, including oily fish. Girls should limit oily fish to two portions weekly (the same as women who might become pregnant), while boys can safely consume up to four portions of oily fish weekly.

Adults: Women who might become pregnant should limit oily fish to two portions weekly, while men and women past childbearing age can consume up to four portions weekly. All adults should aim for at least two fish portions weekly, with one being oily fish. Older adults may benefit from maintaining adequate omega-3 intake, as some observational studies suggest associations between omega-3 consumption and cognitive health, though there is no official link established for preventing dementia.

Individuals with cardiovascular disease: NICE guidance (NG238) does not routinely recommend omega-3 supplements for cardiovascular disease prevention or secondary prevention. However, NICE Technology Appraisal 805 recommends icosapent ethyl (a purified EPA) for selected high-risk patients with elevated triglycerides despite statin therapy. For severe hypertriglyceridaemia, prescription omega-3 preparations may be used under specialist supervision.

Food Sources vs Supplements: Meeting Your Daily Omega-3 Needs

Obtaining omega-3 fatty acids through dietary sources is generally preferable to supplementation, as whole foods provide additional nutrients including protein, vitamins, minerals, and other beneficial compounds.

Marine sources are the richest providers of EPA and DHA. Oily fish varieties particularly high in omega-3s include:

• Salmon (wild or farmed): 1-2g per 100g

• Mackerel: 1.5-2.5g per 100g

• Sardines: 1-2g per 100g

• Herring: 1-2g per 100g

• Fresh tuna: 0.5-1.5g per 100g

• Trout: 0.5-1.5g per 100g

It is worth noting that tinned tuna contains significantly less omega-3 than fresh tuna due to processing methods and is not classified as an oily fish by the NHS. White fish (cod, haddock) contain minimal omega-3 compared to oily varieties.

Plant-based sources provide ALA rather than EPA and DHA. Good sources include:

• Flaxseeds (linseeds): 2.3g per tablespoon (ground)

• Chia seeds: 2.5g per tablespoon

• Walnuts: 2.5g per 30g serving

• Rapeseed oil: 1.3g per tablespoon

• Soya beans and tofu: moderate amounts

Supplements may be appropriate for individuals who cannot or choose not to consume fish, have increased requirements, or have specific medical conditions. Available forms include fish oil capsules, cod liver oil, krill oil, and algal oil (a vegetarian/vegan source of EPA and DHA). When selecting supplements, look for products that specify EPA and DHA content (not just total omega-3), are from reputable manufacturers, and ideally carry quality assurance marks. In the UK, food supplements are regulated under food law by the Department of Health and Social Care and the Food Standards Agency, not as medicines.

Vegetarians, vegans, and those with fish or shellfish allergies may particularly benefit from algal oil supplements, as these provide preformed DHA and EPA without relying on the inefficient conversion from ALA. A typical algal oil supplement provides 200-400mg combined EPA and DHA per capsule.

Safety Considerations and Maximum Daily Limits

Whilst omega-3 fatty acids are generally well-tolerated, certain safety considerations and upper limits should be observed to minimise potential adverse effects.

Common side effects of omega-3 supplementation, particularly at higher doses, include gastrointestinal disturbances such as nausea, loose stools, and fishy aftertaste or reflux. Taking supplements with meals and choosing enteric-coated formulations may reduce these effects. Some individuals report a fishy body odour with high-dose supplementation. If you experience any suspected side effects from supplements, you can report them via the MHRA Yellow Card scheme (yellowcard.mhra.gov.uk).

Bleeding risk is a theoretical concern with high-dose omega-3 intake due to effects on platelet function. Omega-3 fatty acids can reduce platelet aggregation, potentially prolonging bleeding time. However, clinically significant bleeding is rare at typical supplemental doses. Individuals taking anticoagulants (warfarin, DOACs) or antiplatelet medications (aspirin, clopidogrel) should consult their GP or pharmacist before starting omega-3 supplements, particularly at doses exceeding 3g daily. There is no official link between standard omega-3 supplementation and major bleeding events in most individuals, but caution is warranted in those with bleeding disorders or upcoming surgery.

Maximum safe limits: The European Food Safety Authority (EFSA) considers long-chain omega-3 supplementation up to 5g daily (combined EPA and DHA) to be safe for the general adult population. However, the NHS advises against exceeding 3g daily from supplements without medical supervision. High-dose mixed EPA/DHA supplements may raise LDL-cholesterol in some individuals, which may require monitoring if used therapeutically. Doses of 2-4g daily are sometimes prescribed for severe hypertriglyceridaemia, but such therapeutic doses should only be taken under specialist guidance.

Contaminant concerns: Oily fish can accumulate environmental pollutants including mercury, dioxins, and polychlorinated biphenyls (PCBs). This is why the NHS recommends limiting oily fish consumption to two portions weekly for women of childbearing age and four portions for others. Reputable fish oil supplements are typically purified to remove contaminants, but quality varies between manufacturers.

Pregnancy considerations: Pregnant women should avoid cod liver oil and other supplements containing vitamin A (retinol) as these may harm the developing baby. Algal oil supplements may be a suitable alternative.

When to seek medical advice: Contact your GP if you experience persistent gastrointestinal symptoms, unusual bleeding or bruising, or if you are considering omega-3 supplements whilst taking prescribed medications. Pregnant women should discuss supplementation with their midwife or doctor before commencing.

Frequently Asked Questions