This popular nutritional supplement is rich in omega-3 and vitamins D and A. But is eating oily fish a better way to reap the benefits than taking a pill?
Cod liver oil is renowned as a nutrient-dense source of vitamins and essential fatty acids. As the name suggests, it's derived from cod liver and is available as a liquid or capsule supplement. Read on to discover what gives cod liver oil its health-promoting reputation, plus whether a supplement is really the best way to get the benefits.
Nutritional benefits of cod liver oil
The star ingredient in cod liver oil is omega-3, a polyunsaturated fat. Omega-3 is known as an essential fatty acid because the human body is unable to make it, so it's necessary to get it from food.
Omega-3 from fish can be broken down into two different types: eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), which together and individually offer many health benefits. The World Health Organisation recommends eating 1-2 portions of oily fish a week, equivalent to 200-500 mg of EPA and DHA.
Cod liver oil is also a good source of vitamin D, which helps us to absorb calcium and is important for strong bones and teeth.
Can cod liver oil protect against heart disease?
One of the key benefits of omega-3 is its anti-inflammatory effects – as such, it has previously been thought to be useful against diseases which have an inflammatory component such as heart disease. Early studies on omega-3 had suggested a protective benefit for the heart, although a more recent Cochrane review has raised questions over the relevance of supplements to achieve these benefits.
Research from the University of East Anglia has suggested that taking omega-3 supplements over a number of years offers a small protective effect on cardiovascular diseases, but this may be offset by a slightly higher risk of prostate cancer.
Nevertheless, current UK dietary advice remains the same: to help prevent heart disease, the NHS recommends eating two portions of fish per week, of which one should be an oily variety such as salmon, mackerel or trout.
Can cod liver oil help with depression?
There has been a lot of research into the role that omega-3 could play in helping those suffering with depression, often with mixed results, so more research is needed before we can confidently say that omega-3 has a significant impact on mental well-being.
However, we do know that omega-3, and specifically DHA, is important for the brain. Recent animal studies have suggested that omega-3 could play a role in lowering anxiety and improving cognitive function. One small study found that omega-3 may be of benefit to Parkinson’s patients who suffer with depression, with or without antidepressants. A recent pilot study has also suggested that omega-3 fish oil, such as cod liver oil, may be beneficial to children and adolescents with depression.
Can cod liver oil improve memory?
There has been some positive research into the link between omega-3 and memory. In 2012, the Nutrition Journal published a paper that suggested that five weeks of daily omega-3 intake had the potential to improve cognitive function in those aged 51-72 years old.
Can cod liver oil help with asthma?
There has been some interesting research into the role of omega-3 and asthma, but at the moment, more research is needed as there has not been enough consistent evidence to justify this as a dietary recommendation.
Can cod liver oil help me lose weight?
Not exactly, but some early research did demonstrate that taking fish oils as part of a regular exercise programme reduced body fat and improved cardiovascular function and metabolic health.
Can cod liver oil be good for my liver?
Non-alcoholic fatty liver disease, which covers a range of conditions caused by a build-up of fat in the liver, is on the rise in the UK with around 1 in 5 people affected. This is thought in part to be due to an increase in poor diets, obesity and type 2 diabetes. There appears to be some evidence that omega-3 may reduce fat levels in the liver, although the optimal dose is not yet known.
Can cod liver oil help with rheumatoid arthritis?
Thanks to the anti-inflammatory effects of omega-3 and its vitamin D content, it appears that cod liver oil may be of benefit to those with rheumatoid arthritis, helping to reduce pain and the need for certain medications.
A more recent 2013 study looked at the eating habits of 32,000 middle-aged women to see if eating oily fish had any influence on them developing rheumatoid arthritis. The study found that women who ate one or more portions of oily fish per week were 29% less likely to develop the condition than those who never or only rarely ate oily fish. Although interesting, studies such as these have limitations because other factors may have influenced the findings.
Are there any risks to taking cod liver oil?
Omega-3 is generally regarded as safe for most people when taken in low doses, which is 3g total fish oil a day or less. If you are considering taking a new supplement, discuss this with your GP or doctor first, especially if you are taking any prescription medication.
Recent research from the University of East Anglia suggests that taking omega-3 supplements over a number of years may slightly reduce coronary heart disease mortality and events, but slightly increases the risk of prostate cancer. Both the beneficial and harmful effects noted in this study were small.
The NHS advises against taking cod liver oil during pregnancy as it contains too much vitamin A, which can be harmful to a developing baby.
What’s the difference between taking a supplement and eating oily fish?
Supplements tend to provide a concentrated and more convenient dose of omega-3, but there is no current recommended daily allowance (RDA) for omega-3 in the UK. Start by adding oily fish, such as salmon, mackerel and trout to your diet twice a week as it’s always preferable to get nutrients from food before trying a supplement.
How can you choose a good cod liver oil supplement?
As there is no RDA for omega-3 in the UK, it will depend on why you want to take a cod liver oil supplement. If your GP or doctor has agreed that it is safe for you to take, the British Dietetic Association recommends looking for a supplement that contains around 450mg EPA and DHA per daily dose – the daily equivalent of eating one to two portions of oily fish per week.
Most cod liver oil capsules also contain vitamin D and A, so make sure that you're not taking any other supplements such as a multivitamin, or you may exceed the recommended amounts each day.
Some people prefer to take an omega-3 supplement which is produced from the body of oily varieties of fish such as anchovies and sardines. These products do not contain the vitamin A that cod liver oil does – taking too much vitamin A can lead to liver problems and hair loss, and should be avoided if you are pregnant. Fish liver oil which has not been well purified may also contain contaminants including mercury and dioxins. Always choose a product from a reputable supplement company which tests fish liver oil for purity before distribution.
Get omega-3 in these recipes...
Grilled mackerel with soy, lime & ginger
20-minute rice supper
Tuna steaks with cucumber relish
Baked sea bass with lemongrass & ginger
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This article was last reviewed on 10th August 2018 by Kerry Torrens.
A registered nutritionist, Kerry Torrens is a contributing author to a number of nutritional and cookery publications including BBC Good Food magazine. Kerry is a member of the Royal Society of Medicine, the Complementary and Natural Healthcare Council (CNHC), and the British Association for Applied Nutrition and Nutritional Therapy (BANT).
Nicola Shubrook is a nutritional therapist and works with both private clients and the corporate sector. She is an accredited member of the British Association for Applied Nutrition and Nutritional Therapy (BANT) and the Complementary & Natural Healthcare Council (CNHC). Find out more at urbanwellness.co.uk.
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