Omega-3 for heart health: food, fish oil supplements and what the evidence says

Omega-3s are a family of fats. The British Heart Foundation names the three most important to health: alpha-linolenic acid (ALA), found in some nuts and seeds and the oils made from them, and eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), found mainly in oily fish but also in white fish and seafood. ALA is an essential fatty acid, which the body cannot make, and the body can convert some ALA to EPA and DHA, but only in small amounts.

EPA and DHA have been linked to a reduction in the risk of heart disease. The British Heart Foundation says it is thought they could do this in several ways, including reducing triglycerides in the blood, improving circulation, preventing blood clots, lowering blood pressure and maintaining a healthy heart rhythm. The NHS makes the same link, saying long-chain omega-3 in oily fish may help to prevent heart disease.

Omega-3 also has roles outside the heart: the British Heart Foundation notes it is in the membranes of every type of cell and is vital for the development of a baby's brain and retinas, and the NHS says oily fish omega-3 is important during pregnancy and breastfeeding because it can help the baby's nervous system develop.

The British Heart Foundation says oily fish is the best source of EPA and DHA, for example mackerel, salmon, trout, sardines and anchovies, and that fresh, frozen or tinned are all suitable, though smoked, salted or brine-tinned fish should be limited because of added salt. If you do not eat fish, it lists flaxseed, chia seeds, walnuts, rapeseed, soya beans and the oils made from them as sources of ALA, and microalgae-based products containing EPA and DHA are available for vegetarians and vegans.

The NHS fish page explains that oily fish are high in long-chain omega-3, are a good source of vitamin D, and that some types of shellfish such as mussels, oysters, squid and crab contain long-chain omega-3, though not as much as oily fish. White fish, such as cod, haddock and pollock, are low in fat.

NICE's guideline on cardiovascular disease risk assessment and lipid modification (NG238) says not to offer omega 3 fatty acid compounds to prevent cardiovascular disease, and to tell people there is no evidence that they help to prevent it, except for icosapent ethyl as described in a NICE technology appraisal for people with raised triglycerides. It also advises not to offer a combination of a statin with an omega 3 fatty acid compound, apart from the same exception.

The British Heart Foundation says you do not need omega-3 supplements unless your doctor has prescribed them, and that research suggests the benefit comes from food. It describes the evidence on fish oil supplements as mixed. In a June 2024 article it discusses a UK Biobank study of over 400,000 people that found regular fish oil use was associated with a higher chance of atrial fibrillation and stroke in people without heart disease, and a lower chance of other heart problems in people who already had atrial fibrillation or heart failure. As an observational study it could not show cause and effect.

The British Heart Foundation's verdict is that the research should not concern people who regularly take fish oil, but is not a green light to start taking it to prevent heart and circulatory disease.

The British Heart Foundation says to choose products that contain DHA and EPA and not just fish liver oil, and to check how much they contain. It gives roughly 450mg per day as the equivalent you would get from eating the recommended amount of fish. It says to discuss any supplement with your doctor before taking it to avoid interactions with prescribed medicines, which matters especially for fish oil supplements if you take medicines that affect how well your blood clots.

If a supplement contains vitamin A, make sure you are not getting too much from the supplement and diet combined. The British Heart Foundation says too much vitamin A can increase the risk of osteoporosis and that a maximum daily total of 1.5mg is recommended. The NHS adds that, unless your GP advises otherwise, fish liver oil supplements should be avoided when pregnant or trying for a baby because they are high in vitamin A (retinol), which can be harmful to an unborn baby.

People who have heart disease, atrial fibrillation, heart failure, raised triglycerides, or who take medicines that affect blood clotting, are in situations where supplements may interact with their treatment or change their risk, and a GP, pharmacist or dietitian can advise. NICE names icosapent ethyl, a prescription medicine used with a statin for people with raised triglycerides, as the one exception to its advice; that is different from a shop-bought capsule.

The sources used for this page do not compare individual products, so a pharmacist is the best person to ask about a particular supplement.

The NHS places oily fish within a healthy, balanced diet. Other measures that affect cardiovascular risk include not smoking, keeping blood pressure and cholesterol in check, being active, keeping to a healthy weight and limiting alcohol. A GP can assess your cardiovascular risk, which is how a decision about a medicine such as a statin is made.

Dietary advice on fish and omega-3 is general public health guidance. Cardiovascular risk checks and prescription lipid treatments are provided by GPs on the NHS. Supplements are bought privately in shops and online, and NICE does not recommend them for preventing cardiovascular disease, so it is reasonable to spend money on food first.