Sources of omega-3 fatty acids are essential to understand, as these vital nutrients cannot be produced by your body and must be obtained through diet or supplementation. Omega-3s—including EPA, DHA, and ALA—support cardiovascular health, brain function, and normal vision whilst reducing inflammation. The NHS recommends eating at least two portions of fish weekly, including one portion of oily fish, to meet your omega-3 needs. Plant-based sources such as flaxseeds, chia seeds, and walnuts provide ALA, though conversion to EPA and DHA is limited. This article explores the best dietary sources of omega-3 available in the UK, recommended intake levels, and considerations for different population groups.

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 or supplementation. These vital nutrients play important roles in maintaining cardiovascular health, supporting brain function, reducing inflammation, and contributing to normal vision development and maintenance.

There are three main types of omega-3 fatty acids relevant to human health: eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA), and alpha-linolenic acid (ALA). EPA and DHA are long-chain omega-3s found predominantly in marine sources such as oily fish, whilst ALA is a shorter-chain omega-3 found in plant-based foods. The body can convert ALA into EPA and DHA, though this conversion process is relatively inefficient, typically converting only about 5–10% of ALA to EPA and less than 1% to DHA.

Research suggests omega-3 fatty acids offer several health benefits. Regular consumption of oily fish containing omega-3s may help reduce triglyceride levels and lower blood pressure modestly. The NHS and NICE guidance recommend regular consumption of oily fish as part of a balanced diet for heart health, though NICE does not recommend routine omega-3 supplements for preventing cardiovascular disease.

DHA is an important structural component in the brain and contributes to normal brain function. Adequate omega-3 intake during pregnancy supports foetal brain development. DHA also contributes to the maintenance of normal vision, as recognised in the GB Nutrition and Health Claims Register. Additionally, these fatty acids have anti-inflammatory properties, though evidence for benefits varies across different conditions. Ensuring sufficient omega-3 intake through dietary sources is therefore considered an important component of a balanced diet throughout life.

Best Food Sources of Omega-3 in the UK

Oily fish represents the richest and most bioavailable source of EPA and DHA omega-3 fatty acids. The NHS recommends eating at least two portions of fish per week, including one portion (approximately 140g) of oily fish. Common oily fish readily available in UK supermarkets and fishmongers include:

• Salmon – both farmed and wild varieties provide substantial omega-3 content

• Mackerel – an economical option with excellent omega-3 density

• Sardines and pilchards – convenient tinned options that retain omega-3

• Herring – traditional British fish with high omega-3 content

• Trout – particularly rainbow trout, widely available fresh or smoked

• Fresh tuna – note that tinned tuna does not count as oily fish, as canning reduces omega-3 content

A typical 100g portion of cooked salmon provides approximately 1.5-2.5g of combined EPA and DHA, whilst mackerel can provide 1.5-3g per 100g serving, though content varies by species, season and preparation method. These levels contribute meaningfully to cardiovascular health.

Shellfish and other seafood also contribute omega-3s, though generally in lower concentrations than oily fish. Mussels, oysters, crab, and prawns all contain EPA and DHA, making them valuable additions to a varied diet. Fresh or frozen options are widely available across UK retailers.

White fish such as cod, haddock, and plaice contain some omega-3 fatty acids, though at considerably lower levels than oily varieties. Whilst they contribute to overall fish consumption and provide excellent protein and other nutrients, they should not be relied upon as primary omega-3 sources.

The NHS advises specific limits for certain groups: men, boys and women who aren't planning pregnancy can eat up to 4 portions of oily fish weekly, while women who are pregnant, breastfeeding or planning pregnancy should limit oily fish to 2 portions weekly. These groups should also avoid shark, swordfish and marlin due to mercury content, and limit tuna consumption. Fish liver oil supplements should be avoided during pregnancy due to their vitamin A content. When selecting fish, consider sustainability by looking for Marine Stewardship Council (MSC) certification.

Plant-Based and Vegetarian Sources of Omega-3

Individuals following vegetarian, vegan, or plant-based diets can obtain omega-3 fatty acids primarily through ALA-rich foods, though achieving adequate EPA and DHA levels requires more careful dietary planning. Whilst the body converts ALA to EPA and DHA, this process is inefficient, meaning plant-based sources must be consumed in greater quantities or supplementation considered.

Seeds and nuts provide concentrated sources of ALA omega-3:

• Flaxseeds (linseeds) – the richest plant source, with approximately 2-2.5g ALA per tablespoon of ground seeds; using ground/milled flaxseed improves absorption as whole seeds are poorly digested

• Chia seeds – contain roughly 2-2.5g ALA per tablespoon and can be easily incorporated into porridge, smoothies, or baking

• Hemp seeds – provide approximately 1g ALA per tablespoon alongside protein

• Walnuts – about 2.5g ALA per 30g serving (small handful), making them an excellent snacking option

Plant oils derived from omega-3-rich seeds offer convenient ways to increase intake. Flaxseed oil, rapeseed oil, and walnut oil can be used in salad dressings or drizzled over cooked vegetables. Delicate oils like flaxseed and walnut oil are best used unheated as their omega-3 content diminishes with heat. Standard rapeseed oil available in UK supermarkets contains moderate ALA levels and is suitable for everyday cooking within its smoke point.

Fortified foods increasingly available in the UK include plant-based milk alternatives, spreads, and eggs from hens fed omega-3-enriched diets. Some products are fortified with algal oil, providing direct EPA and DHA rather than ALA.

Algae-based supplements represent the only direct plant-derived source of EPA and DHA, as algae are the original producers of these omega-3s in the marine food chain. These supplements suit vegans and vegetarians seeking to ensure adequate long-chain omega-3 intake without relying solely on ALA conversion. When selecting supplements, look for products tested for purity and contaminants, and consult a healthcare professional regarding appropriate dosing, particularly if you have existing health conditions or take medications.

How Much Omega-3 Do You Need Daily?

Official UK guidance on omega-3 intake focuses primarily on food-based recommendations rather than specific numerical targets for individual fatty acids. The NHS advises consuming at least two portions of fish weekly, including one portion of oily fish (approximately 140g), which typically provides 1.5–3g of combined EPA and DHA.

The Scientific Advisory Committee on Nutrition (SACN) has not established a Reference Nutrient Intake (RNI) for omega-3 fatty acids in the UK. The European Food Safety Authority (EFSA) suggests 250mg of combined EPA and DHA daily for cardiovascular health maintenance in adults. For ALA, EFSA recommends approximately 0.5% of total energy intake from this fatty acid.

Special populations have distinct considerations:

• Pregnant and breastfeeding women – the NHS advises eating up to 2 portions of oily fish weekly while avoiding high-mercury species (shark, swordfish, marlin) and limiting tuna consumption. Fish liver oil supplements should be avoided during pregnancy due to their vitamin A content

• Children – boys can have up to 4 portions of oily fish weekly, while girls should limit to 2 portions weekly

• Older adults – maintaining omega-3 intake through regular fish consumption is encouraged as part of a balanced diet

For individuals with high triglycerides, prescription omega-3 medicines may be recommended by healthcare professionals. These include omega-3-acid ethyl esters (Omacor) and icosapent ethyl (Vazkepa), which are prescribed at doses of 2-4g daily. NICE guidance (TA805) recommends icosapent ethyl for specific high-risk patients with cardiovascular disease and elevated triglycerides despite statin treatment. However, NICE does not recommend omega-3 supplements for routine cardiovascular disease prevention.

Practical considerations for meeting omega-3 needs include varying fish choices to balance nutritional benefits with sustainability and contaminant exposure, incorporating plant sources daily for vegetarians, and considering quality-assured supplements when dietary intake is insufficient. If you are taking anticoagulant medications such as warfarin, consult your GP before significantly increasing omega-3 intake or starting supplements, as high doses may affect blood clotting. Similarly, individuals with fish or seafood allergies should seek advice regarding alternative sources and appropriate supplementation strategies. Report any suspected side effects from supplements or medicines to the MHRA Yellow Card Scheme.

Frequently Asked Questions