Omega-3 fatty acids are essential polyunsaturated fats vital for heart, brain, and cellular health. The three main types—alpha-linolenic acid (ALA), eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA)—must be obtained through diet, as your body cannot produce ALA and converts it inefficiently to EPA and DHA. The NHS recommends at least one portion of oily fish weekly, whilst plant-based sources like flaxseeds and walnuts provide ALA. Understanding the best sources of omega-3 fats helps you make informed dietary choices to support cardiovascular function, reduce inflammation, and maintain overall wellbeing within a balanced eating pattern.

What Are Omega-3 Fats and Why Do You Need Them?

Omega-3 fatty acids are a family of polyunsaturated fats that play important roles in the body. Alpha-linolenic acid (ALA) is considered essential because your body cannot produce it, meaning it must be obtained through diet. The other main types are eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), which your body can synthesise from ALA in limited amounts. ALA is found primarily in plant sources, while EPA and DHA are predominantly found in marine sources. EPA and DHA are considered the most biologically active forms.

These fats are integral structural components of cell membranes, particularly in the brain and retina. They also serve as precursors to signalling molecules that help regulate inflammation, blood clotting, and vascular function. While omega-3 fatty acids have anti-inflammatory properties, it's important to understand that both omega-3 and omega-6 fatty acids are necessary for health, rather than one being simply 'good' and the other 'bad'.

The Scientific Advisory Committee on Nutrition (SACN) and the NHS recognise the importance of including sources of omega-3 in a balanced diet, particularly oily fish. Observational studies have associated higher omega-3 consumption with reduced risk of coronary heart disease, though the evidence continues to evolve. The NHS advises that eating oily fish regularly contributes to a balanced diet and may help maintain heart health.

Whilst your body can convert some plant-based ALA into EPA and DHA, this conversion is relatively inefficient—typically less than 10% for EPA and even lower for DHA. This makes direct dietary sources of EPA and DHA particularly valuable, especially for individuals following plant-based diets who may need to consider alternative strategies to meet their omega-3 requirements.

Best Food Sources of Omega-3 Fatty Acids

Marine sources provide the richest concentrations of EPA and DHA. Oily fish are considered the gold standard, with the NHS recommending at least one portion (approximately 140g) weekly. Excellent choices include:

• Salmon (wild or farmed): 1.5–2.5g omega-3 per 100g

• Mackerel: 2.5–3g per 100g

• Sardines: 1.5–2g per 100g

• Herring: 1.5–2g per 100g

• Fresh tuna (not tinned): 1–1.5g per 100g

• Trout: 1–1.5g per 100g

It is worth noting that tinned tuna contains significantly less omega-3 than fresh tuna due to processing methods, and the NHS does not classify tinned tuna as an oily fish. Shellfish such as mussels, oysters, and crab also provide moderate amounts of EPA and DHA, though generally less than oily fish.

Plant-based sources primarily provide ALA, which offers some benefits despite limited conversion to EPA and DHA. Key sources include:

• Flaxseeds (linseeds): 2.3g ALA per tablespoon of ground seeds

• Chia seeds: 2.5g ALA per tablespoon

• Walnuts: 2.5g ALA per 30g serving

• Rapeseed oil: 1.3g ALA per tablespoon

• Soya beans and tofu: moderate ALA content

• Hemp seeds: approximately 1g ALA per tablespoon

For those following vegetarian or vegan diets, algae-based supplements derived from microalgae offer a direct source of DHA and sometimes EPA, bypassing the need for conversion from ALA. These food supplements are increasingly recognised as viable alternatives to fish-derived omega-3s.

Fortified foods are becoming more widely available in the UK, including omega-3 enriched eggs (from hens fed algae or flaxseed), certain spreads, yoghurts, and plant-based milk alternatives. These typically provide smaller amounts compared to whole food sources and should complement rather than replace primary dietary sources.

How Much Omega-3 Do You Need Daily?

The UK does not have a specific Dietary Reference Value (DRV) for omega-3 fatty acids, but guidance from the Scientific Advisory Committee on Nutrition (SACN) provides practical recommendations. For the general adult population, consuming at least two portions of fish weekly, including one portion of oily fish (approximately 140g), is advised. SACN recommends a population average intake of 450mg of long-chain omega-3 fatty acids per day, though individual intakes will vary.

For individuals who do not consume fish, the British Dietetic Association suggests including plant sources of ALA daily, such as flaxseeds, chia seeds, walnuts and rapeseed oil. Those following plant-based diets might also consider algae-based supplements that provide direct sources of EPA and DHA.

Pregnant and breastfeeding women are advised to consume adequate omega-3s to support foetal and infant brain development, but should limit oily fish intake to two portions weekly due to potential pollutant concerns. The Food Standards Agency (FSA) advises pregnant women to avoid shark, swordfish and marlin entirely, and to limit tuna to no more than two tuna steaks (about 140g cooked weight each) or four medium-sized cans per week. Fish liver oil supplements should be avoided during pregnancy due to their high vitamin A content.

Specific clinical populations may have different requirements. The European Food Safety Authority (EFSA) suggests that for cardiovascular health maintenance, intakes of 250mg EPA plus DHA daily may be beneficial. It's important to note that routine omega-3 supplements are not recommended by NICE for cardiovascular disease prevention in the general population. Specific prescription omega-3 products may be recommended for certain high-risk groups, but only under medical supervision.

Children's requirements vary by age. Infants receive DHA through breast milk or fortified formula. As children transition to solid foods, incorporating age-appropriate portions of oily fish (up to two portions weekly for girls and four for boys) helps support neurological development. For those unable to consume fish, paediatric healthcare providers may recommend algae-based supplements, though this should be discussed with a GP or registered dietitian.

While focusing on including good sources of omega-3 fatty acids in your diet is important, the overall dietary pattern matters most. The NHS Eatwell Guide emphasises a balanced approach to eating that includes a variety of foods from all food groups.

Choosing Quality Omega-3 Sources Safely

When selecting omega-3 sources, quality and safety considerations are paramount. For fish, freshness is key—look for bright, clear eyes, firm flesh, and a mild sea smell rather than a strong fishy odour. The Marine Stewardship Council (MSC) certification indicates sustainably sourced seafood, which is increasingly important given concerns about overfishing and marine ecosystem health. Farmed fish can be nutritious and sustainable when sourced responsibly, though omega-3 content may vary depending on feed composition.

Contaminant concerns require attention, particularly regarding mercury, polychlorinated biphenyls (PCBs), and dioxins. Larger, longer-lived predatory fish accumulate higher levels of these substances. The Food Standards Agency (FSA) advises limiting consumption of shark, swordfish, and marlin, especially for pregnant women and young children. Due to pollutant concerns, the FSA recommends that women who are pregnant, planning pregnancy or breastfeeding should eat no more than two portions of oily fish per week. Other adults can eat up to four portions weekly. Smaller fish like sardines and mackerel typically contain lower contaminant levels than larger species.

For supplements, quality varies considerably. Look for products that:

• Display batch testing for purity and potency

• Are certified by independent bodies (e.g., GOED, IFOS) as quality markers

• Clearly state EPA and DHA content per serving

• Use appropriate packaging (dark bottles, blister packs) to prevent oxidation

• Come from reputable manufacturers complying with UK food supplement regulations

Most omega-3 supplements are regulated as foods under UK food law (enforced by Trading Standards), not as medicines. Only licensed omega-3 medicines (which will have a product licence number) are regulated by the MHRA. Rancidity is a common issue with omega-3 supplements—products should not smell strongly fishy or taste unpleasant, as this indicates oxidation, which reduces efficacy and may produce harmful compounds.

Storage matters: keep oils and supplements refrigerated after opening, and consume ground flaxseeds promptly as they oxidise rapidly. Whole flaxseeds can be stored longer but must be ground before consumption for optimal absorption.

When to seek professional advice: Consult your GP or a registered dietitian if you are considering high-dose omega-3 supplements, particularly if you take anticoagulants (warfarin, DOACs), antiplatelet agents (aspirin, clopidogrel), or have a bleeding disorder, as omega-3s may enhance anticoagulant effects. If taking warfarin, your INR should be monitored when starting or stopping high-dose omega-3. Individuals with fish or shellfish allergies should discuss safe alternatives. If you experience persistent gastrointestinal symptoms, fishy aftertaste, or any unexpected effects from supplements, discontinue use and consult your healthcare provider. For prescription omega-3 medicines, report suspected side effects via the MHRA Yellow Card Scheme.

Frequently Asked Questions