Best omega-3 foods include oily fish such as salmon, mackerel, and sardines, which provide the most bioavailable forms of EPA and DHA. Plant-based sources like flaxseeds, chia seeds, and walnuts offer ALA, though conversion to EPA and DHA is limited. The NHS recommends at least one 140g portion of oily fish weekly for adults to support heart, brain, and eye health. Understanding which foods deliver optimal omega-3 content helps you meet nutritional requirements through diet, whether you consume fish or follow a plant-based eating pattern. This guide explores the richest dietary sources available in the UK and practical ways to incorporate them into your meals.

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

Omega-3 fatty acids are essential polyunsaturated fats that your body cannot produce independently, meaning they must be obtained through diet. 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. EPA and DHA are considered the most biologically active forms, playing crucial roles in cellular function throughout the body.

These fatty acids are integral structural components of cell membranes, particularly in the brain and retina. They contribute to maintaining membrane fluidity and support cellular signalling processes. Omega-3s also serve as precursors to eicosanoids—signalling molecules that help regulate inflammation, blood clotting, and immune responses. EPA and DHA contribute to the normal function of the heart, while DHA supports normal brain and eye development in the foetus and breastfed infants.

The NHS recognises the importance of omega-3 fatty acids as part of a balanced diet. ALA can be converted to EPA and DHA in the body, but this conversion is relatively inefficient and varies between individuals (typically around 5-10% for EPA and 2-5% for DHA), which is why direct dietary sources of EPA and DHA are particularly valuable.

The Scientific Advisory Committee on Nutrition (SACN) and the NHS recommend that adults consume at least one portion (approximately 140g) of oily fish per week to meet omega-3 requirements. For those who do not consume fish, alternative sources may be considered, though dietary sources are generally preferred for optimal nutrient absorption and the additional benefits of whole foods.

Top Food Sources of Omega-3 in the UK

Oily fish remains the richest and most bioavailable source of EPA and DHA omega-3 fatty acids. In the UK, readily available options include:

• Salmon (wild or farmed): Provides approximately 2.0–2.5g of omega-3 per 100g serving

• Mackerel: Contains around 2.5–3.0g per 100g, making it one of the most concentrated sources

• Sardines and pilchards: Offer approximately 1.5–2.0g per 100g and are often more affordable

• Herring: Provides roughly 1.5–2.0g per 100g

• Trout (particularly rainbow trout): Contains about 1.0–1.5g per 100g

• Fresh tuna: Offers approximately 0.3–1.5g per 100g

It is important to note that canned tuna does not count as an oily fish because the canning process significantly reduces the omega-3 content. White fish such as cod, haddock, and plaice contain minimal omega-3 compared to oily varieties, though they remain nutritious protein sources.

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

• Flaxseeds (linseeds): Contain approximately 2.3g ALA per tablespoon when ground

• Chia seeds: Provide around 2.5g ALA per tablespoon

• Walnuts: Offer approximately 2.5g ALA per 30g serving

• Rapeseed oil: Contains about 1.3g ALA per tablespoon

• Soya beans and tofu: Provide moderate amounts of ALA

• Green leafy vegetables: Contain small amounts of ALA

Fortified foods are increasingly available in UK supermarkets, including omega-3 enriched eggs (from hens fed flaxseed or algae), certain spreads, and some dairy products. The omega-3 content of these products varies, so check labels for specific amounts. Algae-based supplements provide a direct source of DHA and EPA for those following plant-based diets, as algae is the original source from which fish obtain their omega-3 content.

How Much Omega-3 Should You Eat Daily?

The UK does not have a specific Reference Nutrient Intake (RNI) for omega-3 fatty acids, but guidance from various health bodies provides practical recommendations. The Scientific Advisory Committee on Nutrition (SACN) and NHS suggest that adults should aim to consume at least two portions of fish per week, with one being an oily fish portion of approximately 140g. This typically provides around 2.0–3.0g of combined EPA and DHA weekly, or roughly 280–450mg daily.

For those consuming plant-based sources only, the European Food Safety Authority (EFSA) suggests an adequate intake of approximately 1.1g of ALA daily for women and 1.6g daily for men. Given the limited conversion of ALA to EPA and DHA, individuals following vegetarian or vegan diets may need to consume higher amounts of ALA-rich foods or consider algae-based supplements.

Special populations have specific considerations:

• Pregnant and breastfeeding women: Should aim for adequate omega-3 intake to support foetal and infant brain development, but should limit oily fish to two portions weekly due to potential pollutant concerns. They should also limit tuna to no more than two tuna steaks or four medium-sized cans per week. Shark, swordfish, and marlin should be avoided entirely during pregnancy. Cold-smoked fish (such as smoked salmon) should be thoroughly cooked to reduce listeriosis risk. Avoid cod liver oil supplements during pregnancy due to high vitamin A content.

• Girls and women who might become pregnant in the future: Should also limit oily fish to two portions weekly.

• Men, boys and older women: Can eat up to four portions of oily fish weekly.

• Children: Can be given one to two portions of oily fish weekly, with portion sizes adjusted according to age and appetite.

• Individuals with cardiovascular conditions: Should follow NICE guidance, which does not recommend routine use of omega-3 supplements for cardiovascular disease prevention. Prescription icosapent ethyl may be considered for specific patients with high triglycerides, in line with NICE guidance.

Most omega-3 supplements are regulated as food supplements under food law (not by the MHRA). While supplements can help bridge dietary gaps, they should not replace a varied, balanced diet. Do not exceed the recommended dose on supplement labels. If considering high-dose omega-3, particularly if taking anticoagulant or antiplatelet medications, consult your GP first. Always inform healthcare professionals about any supplements you are taking, especially before surgery.

Tips for Including More Omega-3 Foods in Your Diet

Incorporating omega-3-rich foods into your regular eating pattern need not be complicated or expensive. For fish consumers, consider these practical strategies:

• Plan weekly fish meals: Designate specific days for fish dishes—for example, salmon on Wednesdays and mackerel on Saturdays—to establish a routine. Remember the recommended limits: up to 2 portions of oily fish weekly for women who are pregnant, breastfeeding or might become pregnant; up to 4 portions weekly for men, boys and older women.

• Explore affordable options: Canned sardines, pilchards, and mackerel are economical choices that have long shelf lives and can be added to salads, pasta, or toast. Remember that canned tuna does not count as an oily fish due to its reduced omega-3 content.

• Try different preparations: Grill, bake, poach, or steam fish with herbs and lemon. Smoked mackerel or salmon can be flaked into scrambled eggs or added to jacket potatoes. If pregnant, ensure cold-smoked fish is thoroughly cooked.

• Batch cooking: Prepare larger portions of fish dishes and freeze individual servings for convenient midweek meals.

• Check sustainability: Look for Marine Stewardship Council (MSC) certification to support sustainable fishing practices.

For plant-based eaters, maximising ALA intake requires consistent inclusion of key foods:

• Ground flaxseeds: Add to porridge, smoothies, yoghurt, or baked goods. Whole seeds pass through the digestive system largely undigested, so grinding is essential for absorption.

• Chia seed puddings: Soak chia seeds in plant milk overnight for a nutritious breakfast or snack.

• Walnut snacking: Keep a small portion (approximately 30g) as a daily snack, or chop and sprinkle over salads and cereals.

• Cooking oils: Use rapeseed oil for cooking and flaxseed oil for salad dressings (avoid heating flaxseed oil as it oxidises easily).

• Fortified products: Choose omega-3 enriched eggs, plant milks, and spreads when available, checking labels for actual omega-3 content.

General dietary advice includes eating a variety of omega-3 sources rather than relying on a single food, as this provides a broader range of nutrients. Store omega-3-rich oils in dark, cool places and use within recommended dates, as these fats are susceptible to oxidation. If you have concerns about meeting your omega-3 requirements—particularly if you avoid fish, are pregnant, or have specific health conditions—consult your GP or a registered dietitian for personalised advice. They can assess your individual needs and determine whether dietary adjustments or supplementation may be appropriate. If you experience any suspected side effects from supplements, report them through the MHRA Yellow Card scheme.

Frequently Asked Questions