Best food sources of omega-3 include oily fish such as salmon, mackerel, sardines, and herring, which provide concentrated amounts of EPA and DHA—the long-chain omega-3 fatty acids essential for cardiovascular and brain health. For those following plant-based diets, flaxseeds, chia seeds, walnuts, and rapeseed oil offer alpha-linolenic acid (ALA), which the body partially converts to EPA and DHA. The NHS recommends at least one portion of oily fish weekly, yet most UK adults consume insufficient amounts. Understanding which foods deliver the richest omega-3 content enables informed dietary choices that support long-term wellbeing across all life stages.

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

Omega-3 fatty acids are important polyunsaturated fats that play vital roles in health. They comprise three main types: eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA), and alpha-linolenic acid (ALA). ALA is essential, meaning your body cannot produce it and must obtain it from food. EPA and DHA are long-chain omega-3s that your body can synthesise from ALA, though this conversion is relatively inefficient (typically 5-10% for EPA and less than 1% for DHA).

The physiological importance of omega-3 fatty acids extends across multiple body systems. DHA is a structural component of cell membranes, particularly concentrated in the brain and retina, where it supports cognitive function and visual development. EPA plays a crucial role in producing eicosanoids—signalling molecules that help regulate inflammation, blood clotting, and immune responses. Both EPA and DHA contribute to cardiovascular health by helping to maintain healthy triglyceride levels, supporting normal blood pressure, and reducing arterial stiffness.

According to guidance from the Scientific Advisory Committee on Nutrition (SACN), regular consumption of oily fish containing omega-3 fatty acids is associated with reduced risk of cardiovascular disease, a leading cause of mortality in the UK. Emerging evidence also suggests potential benefits for mental health, with studies investigating omega-3's role in depression and cognitive decline, though further research is needed to establish definitive clinical recommendations.

The UK population generally consumes suboptimal amounts of oily fish, the primary dietary source of EPA and DHA. National Diet and Nutrition Survey data shows that most adults eat well below the recommended one portion of oily fish per week. Understanding which foods provide the richest sources enables individuals to make informed dietary choices that support long-term health and wellbeing.

Best Fish and Seafood Sources of Omega-3

Oily fish represent the most concentrated dietary source of EPA and DHA, making them the cornerstone of omega-3 nutrition. The NHS recommends consuming at least two portions of fish per week, including at least one portion (approximately 140g cooked weight) of oily fish. The richest sources include:

• Salmon (wild and farmed): Provides 1.5–2.5g of omega-3 per 100g serving, with wild varieties typically containing higher concentrations

• Mackerel: Delivers approximately 2.5–3g per 100g, making it one of the most omega-3-dense options

• Sardines and pilchards: Offer 1.5–2g per 100g and are economical, sustainable choices

• Herring: Contains roughly 2g per 100g and is widely available fresh or pickled

• Fresh tuna: Contains varying amounts of omega-3 depending on species, typically 0.5–1.5g per 100g

• Trout: Delivers approximately 1–1.5g per 100g, particularly rainbow trout

Shellfish and other seafood also contribute meaningful amounts of omega-3, though generally at lower concentrations than oily fish. Mussels, oysters, and crab contain moderate levels (0.3–0.7g per 100g), whilst prawns and white fish such as cod provide smaller amounts.

When selecting fish, consider sustainability and contaminant exposure. The Marine Conservation Society's Good Fish Guide helps UK consumers choose responsibly sourced options. Pregnant and breastfeeding women should avoid shark, swordfish and marlin due to mercury content, and limit oily fish intake to two portions weekly. They should also limit tuna to no more than two fresh tuna steaks or four medium-sized cans per week. Girls and women who might become pregnant in the future should also limit oily fish to two portions weekly. For the general population, consuming up to four portions of oily fish weekly and varying fish choices helps minimise potential contaminant exposure whilst maximising nutritional benefits.

Fresh, frozen, and tinned oily fish (in water or oil) all retain significant omega-3 content, making them practical options for regular consumption. However, it's important to note that tinned tuna does not count as an oily fish because the canning process reduces its omega-3 content significantly.

If you have a fish or shellfish allergy, you'll need to consider alternative omega-3 sources discussed in later sections.

Plant-Based Omega-3 Food Sources

For individuals following vegetarian, vegan, or predominantly plant-based diets, ALA-rich foods provide the primary source of omega-3 fatty acids. Whilst the body converts only a small proportion of ALA to EPA and DHA, regular consumption of ALA sources remains important for overall health.

Seeds and their oils represent the most concentrated plant sources:

• Flaxseeds (linseeds): Contain approximately 2.3g of ALA per tablespoon of ground seeds or 7g per tablespoon of flaxseed oil, making them exceptionally rich sources

• Chia seeds: Provide roughly 2.5g of ALA per tablespoon, along with fibre and protein

• Hemp seeds: Deliver about 1g of ALA per tablespoon with a favourable omega-3 to omega-6 ratio

• Walnuts: Offer approximately 2.5g of ALA per 30g serving (small handful)

Leafy green vegetables contain modest amounts of ALA, with Brussels sprouts, kale, and spinach providing 0.1–0.2g per cooked serving. Whilst not primary sources, these vegetables contribute to overall intake when consumed regularly.

Rapeseed oil, commonly used in UK cooking, contains approximately 1g of ALA per tablespoon and represents a practical way to increase omega-3 intake. Soya beans and tofu provide smaller amounts (0.3–0.7g per serving).

Important considerations for plant-based omega-3 nutrition: The conversion of ALA to EPA and DHA is influenced by several factors, including overall diet composition, age, and genetic variations. High intake of omega-6 fatty acids may reduce conversion of ALA to EPA and DHA, so prioritising adequate ALA intake is important. Individuals following strict plant-based diets may wish to consider algae-derived EPA and DHA supplements, which provide direct sources of these long-chain omega-3s without relying on conversion. This is particularly relevant during pregnancy, lactation, and for young children, when DHA requirements are elevated. The NHS and British Dietetic Association acknowledge that algal supplements can be appropriate for those avoiding fish, especially during these life stages.

How Much Omega-3 Do You Need Daily?

UK dietary recommendations for omega-3 intake vary depending on the specific fatty acid type and individual circumstances. The Scientific Advisory Committee on Nutrition (SACN) advises a population recommendation equivalent to approximately 450mg of combined EPA and DHA daily, which corresponds to consuming at least one portion of oily fish per week. The UK has not established specific Reference Nutrient Intakes (RNIs) for EPA and DHA.

For ALA, the reference nutrient intake is approximately 0.2% of total energy intake. For an average adult consuming 2,000 calories daily, this translates to roughly 0.5g of ALA per day, though higher intakes may be beneficial, particularly for those not consuming marine sources of omega-3.

Specific population groups have distinct requirements:

• Pregnant and breastfeeding women: DHA is crucial for foetal brain and eye development. The European Food Safety Authority (EFSA) recommends an additional 100–200mg of DHA daily during pregnancy and lactation, beyond the standard adult recommendation. Pregnant women should avoid cod liver oil supplements due to their high vitamin A (retinol) content, which may harm the unborn baby

• Infants and children: Adequate DHA supports neurodevelopment. Breast milk provides DHA when maternal intake is sufficient; infant formula in the UK is typically fortified with DHA

• Older adults: Some evidence suggests higher omega-3 intake may support cognitive function, though optimal doses remain under investigation

Regarding cardiovascular health, NICE guidance (NG238) does not recommend routine use of 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) for specific high-risk patients already taking statins. This should not be confused with over-the-counter fish oil supplements, which are not equivalent.

The European Food Safety Authority considers combined EPA and DHA intake up to 5g daily from all sources to be safe for the general adult population. However, omega-3 supplements may interact with anticoagulant medications such as warfarin (requiring INR monitoring) or direct oral anticoagulants (DOACs). If you are taking prescribed medications or have existing health conditions, consult your GP or pharmacist before significantly increasing omega-3 intake through supplements.

Tips for Including More Omega-3 in Your UK Diet

Incorporating omega-3-rich foods into your regular eating pattern need not be complicated or expensive. The following practical strategies can help UK residents optimise their omega-3 intake:

For fish and seafood consumers:

• Plan two fish meals weekly, ensuring at least one features oily fish. Tinned mackerel, sardines, or salmon provide convenient, affordable options that require minimal preparation

• Remember that tinned tuna does not count as an oily fish, though it remains a nutritious protein source

• Experiment with different preparations: Grilled mackerel with mustard, sardines on wholemeal toast, or salmon fishcakes offer variety whilst maintaining nutritional benefits

• Choose sustainable options: Consult the Marine Conservation Society's ratings to select environmentally responsible seafood

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

• Be mindful that smoked fish can be high in salt, so consume in moderation

For plant-based eaters:

• Add ground flaxseeds to porridge, yoghurt, or smoothies: Grinding flaxseeds enhances nutrient absorption; whole seeds may pass through the digestive system intact

• Sprinkle chia or hemp seeds on salads and cereals: These versatile seeds integrate easily into existing meals

• Choose rapeseed oil for cooking and salad dressings: Its neutral flavour and high smoke point make it suitable for various culinary applications

• Snack on walnuts: A small handful provides substantial ALA alongside other beneficial nutrients

General dietary strategies:

• Use small amounts of unsaturated oils and spreads: Choose rapeseed or olive oil for cooking and focus on including omega-3 sources in your diet

• Read food labels: Some UK products, including certain eggs, spreads, and dairy items, are fortified with omega-3

• Consider algae-based supplements: Vegetarians, vegans, and those with fish allergies may benefit from direct EPA and DHA sources derived from microalgae

When to seek professional advice: If you have difficulty meeting omega-3 requirements through diet alone or have cardiovascular risk factors, discuss your nutritional needs with your GP or request referral to a registered dietitian. They can provide personalised guidance appropriate to your individual health status and dietary preferences.

If you experience any suspected side effects from omega-3 medicines or supplements, report them through the MHRA Yellow Card scheme.

Frequently Asked Questions