Docosahexaenoic acid (DHA) is a vital omega-3 fatty acid essential for brain, eye, and heart health throughout life. Whilst the body can produce small amounts from plant-based omega-3s, this conversion is highly inefficient. Foods high in DHA—primarily oily fish such as salmon, mackerel, and sardines—provide the most effective way to meet your nutritional needs. Understanding which foods contain DHA and how much you require can help support cognitive function, cardiovascular health, and overall wellbeing. This guide explores the best dietary sources of DHA, recommended intake levels, and practical ways to incorporate this essential nutrient into your diet.

What Is DHA and Why Is It Important for Health?

Docosahexaenoic acid (DHA) is a long-chain omega-3 polyunsaturated fatty acid that plays a crucial structural and functional role in human health. As an essential component of cell membranes throughout the body, DHA is particularly concentrated in the brain, retina, and heart tissue. The human body can synthesise small amounts of DHA from alpha-linolenic acid (ALA), another omega-3 fatty acid found in plant sources, but this conversion process is very inefficient—typically less than 1% in adults. Therefore, obtaining DHA directly from dietary sources is considered the most effective way to maintain adequate levels.

DHA is vital for neurological development and function across the lifespan. During pregnancy and early childhood, DHA accumulates rapidly in the developing brain and eyes, supporting cognitive development, visual acuity, and neural connectivity. In adults, adequate DHA intake is associated with maintained cognitive function, reduced inflammation, and cardiovascular health. The fatty acid contributes to membrane fluidity, which affects neurotransmitter signalling, receptor function, and cellular communication.

Research suggests that DHA may play a protective role in several chronic conditions, including cardiovascular disease, age-related cognitive decline, and inflammatory disorders. DHA has anti-inflammatory properties that may help regulate immune responses and tissue repair. According to the National Diet and Nutrition Survey (NDNS), many individuals in the UK do not consume sufficient oily fish—the primary dietary source of DHA. Understanding which foods are rich in this essential fatty acid can help inform dietary choices that support long-term health and wellbeing.

Top Food Sources High in DHA

Oily fish represent the richest and most bioavailable dietary sources of DHA. The following marine species are particularly high in this omega-3 fatty acid, with values based on UK Composition of Foods Integrated Dataset (CoFID):

• Salmon (farmed and wild): Provides approximately 1,000–2,000 mg of DHA per 100g serving, with wild-caught varieties typically containing higher concentrations

• Mackerel: Contains around 1,400–1,800 mg of DHA per 100g, making it one of the most concentrated sources

• Herring: Offers approximately 1,000–1,500 mg of DHA per 100g portion

• Sardines: Provide roughly 700–1,000 mg of DHA per 100g, and are also rich in calcium when consumed with bones

• Anchovies: Contain about 900–1,200 mg of DHA per 100g

• Trout (particularly rainbow trout): Supplies approximately 500–800 mg of DHA per 100g

Other marine sources include:

• Tuna: Fresh tuna contains 200–900 mg per 100g depending on species and counts as an oily fish; tinned tuna contains less due to processing and does not count as an oily fish portion

• Mussels, oysters, and other shellfish: Provide moderate amounts of DHA (100–300 mg per 100g)

• Cod liver oil: A concentrated supplement source providing approximately 500–1,000 mg of DHA per tablespoon. Note: Pregnant women or those trying to conceive should avoid cod liver oil supplements due to their high vitamin A content

Algae-based sources offer a suitable alternative for vegetarians and vegans. Certain microalgae species naturally produce DHA, and supplements derived from these sources provide comparable bioavailability to fish-based DHA. Some fortified foods—including certain eggs, milk, yoghurt, and spreads—are now enriched with DHA from algal sources, though concentrations vary considerably between products. DHA content may not always be declared on labels; check product nutrition information or manufacturer websites for specific details.

NHS guidance recommends that women and girls should eat no more than 2 portions of oily fish per week, while men and boys can eat up to 4 portions weekly. Pregnant women should avoid shark, swordfish and marlin completely, and limit tuna to no more than 2 fresh steaks or 4 medium cans per week.

How Much DHA Do You Need Daily?

There is currently no official UK Reference Nutrient Intake (RNI) specifically for DHA. However, several authoritative bodies provide guidance on omega-3 fatty acid intake. The Scientific Advisory Committee on Nutrition (SACN) recommends that adults consume at least two portions of fish per week, one of which should be oily fish (approximately 140g cooked weight). According to the British Nutrition Foundation, this equates to roughly 450 mg of combined EPA (eicosapentaenoic acid) and DHA per day.

The European Food Safety Authority (EFSA) suggests that an intake of 250 mg per day of combined EPA and DHA is adequate for maintaining cardiovascular health in adults. For health claims related to cognitive and visual function, EFSA indicates that 250 mg of DHA specifically is required. During pregnancy and lactation, requirements increase—EFSA advises an additional 100–200 mg of DHA daily to support foetal and infant brain development, on top of the baseline 250 mg EPA+DHA recommendation, bringing the total to approximately 350–450 mg per day.

Infants and children have specific needs that vary by age. Breast milk naturally contains DHA, with concentrations dependent on maternal intake. For formula-fed infants, UK regulations (retained EU law: Commission Delegated Regulation 2016/127 as applicable in GB) require infant formula to contain DHA at levels of 20–50 mg per 100 kcal. Toddlers and children benefit from regular consumption of fish, with age-appropriate portion sizes recommended by the NHS.

Certain population groups may have different requirements. However, it's important to note that NICE does not routinely recommend omega-3 supplements for cardiovascular disease prevention. If you are unable to meet DHA requirements through diet alone, supplementation with fish oil or algal oil may be considered, but always consult your GP or a registered dietitian before starting any supplement regimen, especially if you are taking anticoagulant medications or have a bleeding disorder. If you experience any side effects from supplements, report them to the MHRA Yellow Card scheme (yellowcard.mhra.gov.uk).

Health Benefits of Including DHA-Rich Foods in Your Diet

Regular consumption of DHA-rich foods is associated with several evidence-based health benefits across multiple physiological systems. In terms of cardiovascular health, observational studies suggest that adequate DHA intake as part of a balanced diet may help reduce triglyceride levels, lower blood pressure modestly, and decrease the risk of coronary heart disease. The NHS and NICE (NG238) recommend eating at least two portions of fish per week, including one oily fish, as part of a heart-healthy dietary pattern. It's worth noting that NICE does not recommend routine omega-3 supplementation for cardiovascular disease prevention.

Cognitive function and mental health represent another key area of potential benefit. DHA is the predominant omega-3 fatty acid in the brain, comprising approximately 40% of polyunsaturated fatty acids in neuronal membranes. Adequate DHA status during pregnancy and early life is important for optimal neurodevelopment, with maternal DHA intake linked to improved cognitive and visual outcomes in offspring. In adults, higher DHA levels are associated with better memory, processing speed, and executive function. Evidence for DHA supplementation in preventing dementia remains inconclusive, though maintaining adequate dietary intake throughout life may support cognitive health during ageing.

DHA also plays a role in eye health, particularly in maintaining retinal structure and function. The retina contains high concentrations of DHA, which supports photoreceptor membrane integrity and visual signal transduction. Some research suggests associations between adequate DHA intake and eye health, though more studies are needed to establish definitive protective effects.

DHA has anti-inflammatory properties that may be beneficial in various conditions. Additionally, some studies have investigated potential benefits for mood disorders, with mixed results regarding omega-3 supplementation and depressive symptoms. Any supplementation should not replace conventional treatment and should be discussed with healthcare professionals.

To maximise potential benefits, aim to include fish at least twice weekly (including one oily fish portion) as part of a balanced diet rich in fruits, vegetables, whole grains, and lean proteins. Remember that women and girls should limit oily fish to 2 portions weekly, while men and boys can have up to 4 portions. If you have specific health concerns or dietary restrictions, consult your GP or a registered dietitian for personalised advice on meeting your DHA requirements safely and effectively.

Frequently Asked Questions