Omega-3 fatty acids daily requirement varies by age, health status, and dietary pattern, but UK guidance recommends at least 450 mg of combined EPA and DHA per day for adults. These essential polyunsaturated fats—alpha-linolenic acid (ALA), eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA)—cannot be synthesised by the body and must be obtained through diet or supplementation. Omega-3s support cardiovascular health, brain development, and inflammatory regulation. The NHS advises consuming at least two portions of fish weekly, including one portion of oily fish, to meet these requirements. Understanding your individual omega-3 needs helps ensure optimal health outcomes.

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

Omega-3 fatty acids are essential polyunsaturated fats that the human body cannot synthesise independently, making dietary intake crucial for health. The three main types of omega-3 fatty acids are alpha-linolenic acid (ALA), eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA). ALA is found primarily in plant sources, whilst EPA and DHA are predominantly obtained from marine sources.

These fatty acids play vital roles throughout the body. DHA is an important structural component of the brain and retina, where it is found in significant concentrations. This makes adequate omega-3 intake particularly important during foetal development, infancy, and childhood for optimal neurological and visual development. EPA and DHA also serve as precursors to specialised pro-resolving mediators (SPMs), which are involved in inflammatory response regulation, though clinical benefits of this mechanism remain under investigation.

Omega-3 fatty acids contribute to cardiovascular health through various physiological processes. At higher intakes (approximately 2-3g daily), they can help reduce triglyceride levels and support blood pressure regulation. They are incorporated into cell membranes, influencing membrane fluidity and cellular signalling pathways. The evidence regarding omega-3s and cardiac arrhythmias is mixed, with some studies suggesting potential benefits while others indicate possible increased risk of atrial fibrillation at high doses. Research into omega-3s and mental health continues, with some evidence suggesting potential benefits for mood regulation.

The body can convert ALA to EPA and DHA, but this conversion is inefficient—typically around 5-10% for EPA and approximately 0.5-5% for DHA, with variation between individuals. This limited conversion capacity means that obtaining EPA and DHA directly from dietary sources is more effective for meeting physiological requirements, particularly for individuals following plant-based diets who may need to consider supplementation or fortified foods.

Daily Omega-3 Requirements: UK Guidelines and Recommendations

The UK does not have a single, universally mandated daily requirement for omega-3 fatty acids, but several authoritative bodies provide guidance. The Scientific Advisory Committee on Nutrition (SACN) recommends a population average intake of 450 mg of combined EPA and DHA per day. This aligns with the practical NHS advice to consume at least two portions of fish per week, including one portion of oily fish.

For alpha-linolenic acid (ALA), the UK does not have a specific Reference Nutrient Intake (RNI). The European Food Safety Authority (EFSA) suggests an adequate intake of approximately 0.5% of total energy intake. For an average adult consuming 2,000 calories daily, this equates to roughly 1.1 grams of ALA per day. However, because ALA conversion to EPA and DHA is limited, this should not be considered a substitute for direct EPA and DHA intake.

The European Food Safety Authority (EFSA) recommends 250 mg of combined EPA and DHA daily for general cardiovascular health maintenance in adults. For pregnant and breastfeeding women, an additional 100–200 mg of DHA per day is recommended to support foetal and infant brain development.

NHS guidance emphasises consuming at least two portions of fish per week, including one portion of oily fish (such as salmon, mackerel, or sardines). A standard portion is approximately 140 grams for adults. The NHS advises that most people can eat up to four portions of oily fish weekly, though this is reduced to two portions for girls, women planning pregnancy, or those who are pregnant or breastfeeding.

It is important to note that NICE guidance (NG238) does not routinely recommend omega-3 fatty acid supplements for primary or secondary prevention of cardiovascular disease in the general population. Higher doses may be prescribed for specific clinical indications, such as hypertriglyceridaemia, but only under medical supervision.

Best Dietary Sources of Omega-3 Fatty Acids

Oily fish remains the most efficient dietary source of EPA and DHA. Species particularly rich in omega-3s include salmon, mackerel, herring, sardines, pilchards, trout, and fresh tuna. A 140-gram portion of cooked salmon typically provides approximately 2–3 grams of combined EPA and DHA, well exceeding daily requirements. Mackerel and herring offer similar concentrations, making them excellent choices for meeting omega-3 needs.

Tinned fish can also contribute significantly to omega-3 intake, though concentrations vary. Tinned sardines, pilchards, and salmon retain substantial omega-3 content, whilst tinned tuna contains lower amounts due to processing methods and the species typically used. It's worth noting that whilst fresh tuna counts as an oily fish, tinned tuna does not count towards your oily fish intake according to NHS guidance. When selecting tinned fish, options preserved in water or olive oil generally have lower salt content than those in brine.

For individuals following plant-based diets, ALA sources include flaxseeds (linseeds), chia seeds, hemp seeds, walnuts, and their respective oils. Rapeseed oil and soya products also provide ALA. Two tablespoons of ground flaxseed or one tablespoon of flaxseed oil can provide approximately 3–4 grams of ALA. However, given the poor conversion efficiency to EPA and DHA, plant-based consumers should consider algae-derived omega-3 supplements, which provide direct sources of EPA and DHA without marine products.

Fortified foods are increasingly available in the UK market, including omega-3 enriched eggs (from hens fed omega-3 rich diets), certain spreads, yoghurts, and plant-based milk alternatives. Whilst these can contribute to overall intake, they typically provide smaller amounts compared to oily fish or supplements.

When incorporating omega-3 rich foods, consider preparation methods. Grilling, baking, or steaming fish preserves omega-3 content better than deep frying. Store omega-3 rich oils in dark, cool places and use within recommended timeframes, as these fats are susceptible to oxidation, which reduces their nutritional value.

Who May Need Higher Omega-3 Intake?

Pregnant and breastfeeding women require additional omega-3 fatty acids, particularly DHA, to support foetal brain and eye development. The foetal brain accumulates DHA rapidly during the third trimester, and breast milk DHA content depends on maternal intake. UK guidance recommends an additional 100–200 mg of DHA daily during pregnancy and lactation. However, pregnant women should limit oily fish consumption to two portions weekly, limit tuna (maximum of two tuna steaks or four medium-sized cans per week), and avoid certain species (shark, swordfish, marlin) due to potential mercury contamination. Fish liver oil supplements should also be avoided during pregnancy due to their high vitamin A content, which may harm the developing baby.

Individuals with cardiovascular conditions may benefit from higher omega-3 intake in specific circumstances, though recommendations should be individualised. Those with hypertriglyceridaemia may require 2–4 grams of EPA and DHA daily under medical supervision. NICE has approved icosapent ethyl (Vazkepa) for reducing cardiovascular risk in certain high-risk patients with elevated triglycerides, but this is a prescription-only medicine. NICE guidance does not routinely recommend omega-3 supplements for primary or secondary prevention of cardiovascular disease in the general population.

People following vegetarian or vegan diets face challenges obtaining adequate EPA and DHA, as plant sources provide only ALA. Whilst ALA has independent health benefits, the limited conversion to EPA and DHA means these individuals may have lower blood levels of these important fatty acids. Algae-based supplements offering 200–300 mg of combined EPA and DHA daily can help bridge this gap. Those following plant-based diets, particularly during pregnancy or breastfeeding, should discuss omega-3 supplementation with their healthcare provider.

Older adults may benefit from maintaining adequate omega-3 intake, though evidence regarding cognitive function and age-related cognitive decline remains evolving. Some research suggests potential benefits for reducing inflammation associated with conditions like rheumatoid arthritis, though evidence is mixed and there is no established recommendation for routine supplementation in all inflammatory conditions.

If you are considering omega-3 supplementation for a specific health condition, consult your GP or a registered dietitian for personalised advice. High-dose omega-3 supplements can interact with anticoagulant and antiplatelet medications and may increase bleeding risk. People taking warfarin should have their INR monitored when starting or changing omega-3 supplement doses. If you experience any side effects from omega-3 supplements or medicines, report them through the MHRA Yellow Card scheme.

Frequently Asked Questions