Foods rich in omega-3 fats provide essential polyunsaturated fatty acids that support heart health, brain function, and inflammatory processes throughout the body. 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 them in sufficient amounts. Oily fish such as salmon, mackerel, and sardines offer the richest sources of EPA and DHA, whilst plant-based options including flaxseeds, chia seeds, and walnuts provide ALA. The NHS recommends eating at least two portions of fish weekly, including one portion of oily fish, as part of a balanced diet to maintain adequate omega-3 intake.

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

Omega-3 fatty acids are essential polyunsaturated fats that your body cannot produce in sufficient amounts, meaning they must be obtained primarily through diet. These nutrients play important roles in maintaining heart health, supporting brain function, and influencing inflammatory processes throughout the body. The three main types of omega-3 fatty acids are alpha-linolenic acid (ALA), found primarily in plant sources; eicosapentaenoic acid (EPA); and docosahexaenoic acid (DHA), both predominantly found in marine sources.

Research suggests that omega-3 fatty acids contribute to overall health, with the NHS and Scientific Advisory Committee on Nutrition (SACN) recommending regular consumption of oily fish as part of a balanced diet. EPA and DHA help maintain cell membrane integrity and produce signalling molecules called eicosanoids that influence blood clotting and inflammatory pathways. DHA is especially concentrated in the brain and retina, making it important for neurological development and visual function.

The body can convert ALA to EPA and DHA, but this conversion is relatively inefficient—typically less than 10% for EPA and even lower for DHA. This limited conversion means that obtaining preformed EPA and DHA directly from dietary sources can be beneficial. True essential fatty acid deficiency is rare in the UK, but ensuring adequate omega-3 intake forms part of dietary recommendations alongside other lifestyle modifications for general health maintenance. The NHS recommends eating at least one portion of oily fish per week as part of a healthy, balanced diet.

Best Food Sources of Omega-3 Fatty Acids

Oily fish represents the richest dietary source of EPA and DHA, with the NHS recommending at least two portions of fish weekly, including one portion (approximately 140g) of oily fish. Excellent choices include:

• Salmon (wild or farmed): provides significant omega-3 content

• Mackerel: particularly rich in omega-3 fatty acids

• Sardines: good source of omega-3, especially when eaten with bones

• Herring: high omega-3 content including in forms like kippers

• Fresh tuna: contains omega-3, though levels vary by species

• Trout: offers good omega-3 content

It is worth noting that tinned tuna is not classified as an oily fish by the NHS due to the processing methods that reduce its omega-3 content. Anchovies and pilchards also provide substantial amounts of these beneficial fats.

Plant-based sources primarily provide ALA and include:

• Flaxseeds (linseeds): Ground flaxseed is one of the richest plant sources of ALA

• Chia seeds: Contain significant amounts of ALA

• Walnuts: Good source of plant-based omega-3

• Hemp seeds: Provide ALA along with other nutrients

• Rapeseed oil: Contains more ALA than most other cooking oils

Fortified foods have become increasingly available in UK supermarkets, including omega-3 enriched eggs (from hens fed flaxseed), certain spreads, yoghurts, and plant-based milk alternatives. These can contribute to overall intake, particularly for individuals following vegetarian or vegan diets.

Shellfish such as oysters, mussels, and crab also contain moderate amounts of EPA and DHA, though generally less than oily fish. When selecting fish, consider sustainability and mercury content—the Marine Conservation Society provides guidance on environmentally responsible choices through their Good Fish Guide.

How Much Omega-3 Do You Need Daily?

The UK does not have a specific recommended nutrient intake (RNI) for omega-3 fatty acids. However, the Scientific Advisory Committee on Nutrition (SACN) suggests a population recommendation of approximately 450mg of combined EPA and DHA daily. This translates to the NHS practical advice of eating at least two portions of fish per week, one of which should be oily.

For ALA (the plant-based omega-3), the UK has not established specific dietary reference values. Different international bodies suggest varying intake levels, but these are not official UK recommendations.

Pregnant and breastfeeding women should continue to eat fish as part of a healthy diet, but should limit oily fish to no more than two portions weekly due to potential pollutant exposure. The NHS advises pregnant women to avoid shark, swordfish, and marlin entirely due to mercury content. Tuna intake should be limited to no more than two tuna steaks (about 140g cooked or 170g raw) or four medium-sized cans per week. Fish liver oil supplements should also be avoided during pregnancy due to their high vitamin A content.

Regarding cardiovascular health, NICE does not recommend routine omega-3 supplements for primary or secondary prevention of cardiovascular disease. However, NICE Technology Appraisal 805 recommends icosapent ethyl (a prescription-only, highly purified EPA) at a dose of 2g twice daily for specific high-risk patients already taking statins. This should only be prescribed by specialists for eligible patients.

Children's requirements vary by age, with infants obtaining omega-3 through breast milk or fortified formula. Older children should be encouraged to consume fish regularly, with portion sizes adjusted according to age.

It is important to note that high-dose omega-3 supplements (particularly exceeding 3g daily) may affect blood clotting and should be discussed with a GP, especially for individuals taking anticoagulant medications such as warfarin (where INR monitoring may be needed) or antiplatelet drugs. Those planning surgery should also inform their healthcare team about omega-3 supplement use.

Plant-Based vs Fish Sources: Understanding the Difference

The distinction between plant-based and marine omega-3 sources centres on the type of fatty acid provided and the body's ability to utilise them effectively. Plant sources predominantly supply ALA, whilst fish and seafood provide the longer-chain EPA and DHA. This difference has implications for meeting your omega-3 requirements.

Conversion efficiency represents a key consideration with plant-based omega-3. The human body must convert ALA to EPA and subsequently to DHA through a series of enzymatic reactions. However, this conversion is relatively limited—research suggests approximately 5–10% of ALA is converted to EPA, and less than 5% reaches DHA. This conversion rate can be influenced by several factors including age, sex (women typically convert more efficiently than men), overall diet composition, and genetic variations in the enzymes involved. High intake of omega-6 fatty acids (common in Western diets) may compete for the same enzymes, though the clinical significance of this competition remains under investigation.

For individuals following vegetarian or vegan diets, meeting omega-3 requirements requires particular attention. Consuming generous amounts of ALA-rich foods daily is important. Algae-based supplements, derived from microalgae that fish consume to obtain their omega-3 content, provide a plant-based source of preformed EPA and DHA and represent a viable alternative for those avoiding fish.

Bioavailability also differs between sources. The omega-3 in fish is readily available to the body, whilst plant sources may benefit from processing (such as grinding flaxseeds) to maximise absorption. Additionally, fish provides other beneficial nutrients including vitamin D, selenium, and high-quality protein.

The NHS continues to recommend fish consumption, particularly oily fish, as part of a healthy diet. Individuals concerned about meeting their requirements should discuss their dietary pattern with a healthcare professional or registered dietitian.

Tips for Including More Omega-3 Foods in Your Diet

Incorporating omega-3-rich foods into your daily routine need not be complicated or expensive. For fish consumers, aim to include fish twice weekly, with at least one portion being oily fish:

• Prepare simple meals: Grilled mackerel with vegetables, baked salmon with herbs, or sardines on wholegrain toast provide quick, nutritious options

• Choose tinned options: Tinned sardines, mackerel, and salmon (with bones for added calcium) offer convenient, affordable alternatives to fresh fish

• Experiment with recipes: Fish curries, pasta dishes with anchovies, or smoked mackerel pâté add variety

• Consider frozen fish: Nutritionally equivalent to fresh, frozen fish is often more economical and reduces waste

The NHS advises most adults can safely eat up to four portions of oily fish weekly, but women who are pregnant, breastfeeding or planning pregnancy, and girls should limit oily fish to two portions weekly.

For plant-based sources, practical strategies include:

• Adding ground flaxseed to porridge, smoothies, yoghurt, or baked goods (whole flaxseeds pass through the digestive system largely undigested)

• Sprinkling chia seeds on cereals, salads, or incorporating them into puddings

• Snacking on walnuts or adding them to salads and baking

• Using rapeseed oil for cooking and salad dressings instead of other vegetable oils

• Choosing omega-3 enriched foods such as certain eggs, spreads, and fortified plant milks

Storage and preparation matter for preserving omega-3 content. Store flaxseed and chia seeds in airtight containers in cool, dark places or refrigerate ground flaxseed. When cooking fish, gentler methods such as baking, steaming, or poaching better preserve omega-3 content compared to high-temperature frying.

For those considering supplements, whole foods remain the preferred source of nutrients. If you are taking anticoagulant or antiplatelet medication, have a bleeding disorder, or are planning surgery, consult your GP before starting omega-3 supplements. People taking warfarin may need additional INR monitoring. Pregnant women should avoid fish liver oil supplements due to their high vitamin A content. If you experience any suspected adverse effects from supplements, report them through the MHRA Yellow Card scheme. Individuals with fish or shellfish allergies should seek specialist dietary advice to ensure adequate omega-3 intake through alternative sources.

Frequently Asked Questions