Guide to cod liver oil

Cod liver oil is an old favourite in our medicine cabinets, popular for everything from creaky joints to brain, eye and heart health.

Because cod liver oil contains omega 3 fatty acids (EPA and DHA), it also acts as an anti-inflammatory agent. This means it may help ease pain in your joints if you have arthritis and may support heart health, although the evidence is mixed.

DHA is found in high concentrations in the brain and eyes where, according to experts, it is linked to better development and function.

Dr Sarah Brewer says: ‘Cod liver oil is as important to health now as it was when our grandparents were young. As a nation, the UK doesn’t consume a lot of fish, so supplements are a good source of omega 3 fatty acids with their anti-inflammatory effects, plus vitamins A and D which provide additional health benefits.

‘If you have arthritis in any form taking omega 3 fatty acids in oily fish or cod liver oil capsules as well as having a healthy diet, may improve things.’

What does cod liver oil do?

Cod liver oil’s health benefits come from its high levels of EPA and DHA, which are anti-inflammatory. It is also a rich source of vitamin D which the body needs to absorb calcium for strong bones and teeth, as well as for a healthy immune system; and vitamin A which is important for eye health.


Cod liver oil supplements have been shown to reduce use of non-steroidal anti-inflammatory drugs (NSAIDs) in people with rheumatoid arthritis (RA), an autoimmune condition where the body produces antibodies which attack the joints. In another study 68 per cent of people with RA who took cod liver oil supplements rated them as good or very good and the supplements were well tolerated.

Osteoarthritis (OA) occurs when the cartilage that cushions your joints wears thin. There’s not any published trial evidence to say cod liver oil supplements help with OA symptoms. However, an unpublished Cardiff study found that in 86 per cent of patients undergoing knee replacement operations, an enzyme that causes damage to cartilage was either absent or reduced if they had been taking 2,000mg of cod liver oil prior to the operation, compared to 26 per cent taking a placebo pill.

Heart health

Research into the benefits of omega 3 fatty acids for people with heart disease began with studies of the Inuit people in Greenland, who ate mainly sea birds, whales, seals and fish. The study authors hypothesised the fish element of their diet, was providing some protection for their hearts.

Studies have found that taking omega 3 fatty acids could reduce the incidence of heart failure and deaths in older people. However evidence on fish oils and prevention of heart attacks is mixed, and the UK’s National Institute of Health Care and Excellence (NICE) do not recommend taking fish oil supplements for preventing subsequent heart attacks in people who have already had one.

Getting cod liver oil from your diet

Cod liver oil is extracted from the liver of Atlantic cod so it’s difficult to obtain from the diet, which is why supplements are a useful alternative.

Dietary sources of vitamin D include oily fish such as mackerel, salmon and fresh tuna, red meat, liver, egg yolks and foods fortified with vitamin D including some breakfast cereals and margarines. Vitamin A can be found in cheese, eggs, oily fish, fortified margarines, milk, yoghurt, liver and liver products.


Cod liver oil contains vitamins A and D, which can be toxic in large doses. The maximum daily dose of vitamin D set is 100mcg. The upper daily safe limit for vitamin A is 3g in adults and 1,500mcg for post-menopausal women (who are at higher risk of bone fractures from too much). If you are also taking a multivitamin, check the vitamin A content, if you are also taking vitamin A supplements.

Don’t take cod liver oil supplements when you are pregnant or trying for a baby. These are high in retinol (vitamin A) which can be harmful to eye development in unborn babies. Also avoid taking multi-vitamins which contain vitamin A.

If you are taking the blood-thinning medication warfarin, check with your doctor before taking cod liver oil to see if it’s safe, as it may intensify the effects of the drugs.

Correct dosage

An intake of 250mg per day for adults of EPA/DHA combination from fish oil is recommended by the European Food Safety Authority.

You can take up to two high-strength cod liver oil capsules each containing 1,000mg a day unless you’ve been advised otherwise by your doctor.

Nothing beats a healthy, balanced diet to provide all the nutrients we need. But when this isn't possible, supplements can help. This article isn't intended to replace medical advice. Please consult your healthcare professional before trying supplements or herbal medicines.

As a nation, the UK doesn’t consume a lot of fish, so supplements are a good source of omega 3 fatty acids with their anti-inflammatory effects, plus vitamins A and D which provide additional health benefits.

Dr Sarah Brewer


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