Magazine subscription 5 issues for only 5 Nutritional therapist Nicola Shubrook explores whether cod liver oil is good for you, offering insights into key nutritional benefits, possible risks and what to look for when considering supplements.
What is cod liver oil?
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
A 1,000mg serving provides approximately:
- 144mg EPA
- 107mg DHA
- 800g vitamin A
- 10g vitamin D
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 offer many health benefits, together and individually. 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 A, which is vital for skin and eye health, and immunity. It also offers vitamin D, which supports calcium absorption and is important for strong bones and teeth.
1. Supports heart health
The omega-3 fatty acids found in cod liver oil have many properties, which make them heart healthy. Studies have shown that omega-3 fatty acids may help to reduce triglycerides, increase healthier HDL cholesterol and lower blood pressure. While most of the research suggests that consuming fish oil such as cod liver oil can reduce certain factors associated with heart disease, more evidence is required in order to conclude whether fish oil has a preventative effect. Nevertheless, current UK dietary advice remains the same: to help prevent heart disease, the NHS recommends eating two portions of fish per week, and one should be an oily variety such as salmon, mackerel or trout.
2. Mood boosting
Omega-3, and specifically DHA, is an important brain nutrient. Studies have shown that omega-3 could play a role in lowering anxiety and improving cognitive function. In a large study of 21,835 participants, those who regularly consumed cod liver oil were shown to have fewer depressive symptoms. Furthermore, a clinical trial of medical students showed that supplementation of omega-3 fatty acids lowered inflammation and resulted in fewer symptoms of anxiety over 12- weeks.
With this said, several similar studies found little or no effect of fish oils on mood and so more research is required to fully understand the mechanisms behind these associations.
4. Supports bone health
Cod liver oil is a great source of vitamin D, which is required to help the body to absorb calcium a vital bone supportive mineral from the gut. As such, adequate vitamin D and efficient calcium utilisation may help to reduce age- related bone loss.
5. Good for your 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. Evidence suggests that omega-3, found in cod liver oil, may reduce fat levels in the liver, although the optimal dose is not yet known.
6. May be beneficial for rheumatoid arthritis
Thanks to the anti-inflammatory effects of omega-3 and vitamin D, 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 study looking at the eating habits of 32,000 middle-aged women found that those who ate one or more portions of oily fish per week were 29% less likely to develop the rheumatoid arthritis than those who never or only rarely ate oily fish.
Are there any risks to taking cod liver oil?
Omega-3 is generally regarded as safe for most people when taken in low doses approximately 3g total fish oil per day or less. If you are considering taking a new supplement, discuss this with your health practitioner first, especially if you are taking any prescription medication. It should be noted that the NHS advises against taking cod liver oil during pregnancy as the high level of vitamin A contain may cause risk to the developing foetus. It is best to speak to your doctor about your options if you are pregnant or looking to conceive.
What's the difference between taking a supplement and eating oily fish?
Supplements provide a concentrated, and often more convenient, dose of omega-3 for those who may not be able to sufficiently cover their needs through diet. With that said, it is always preferable to attain nutrition through food first and choose supplements only when additional support is required.
How can I 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 equivalent of eating one to two portions of oily fish per week. Most cod liver oil capsules will 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. It is always important to choose a product from a reputable supplement company which tests fish liver oil for purity before distribution, as those which have not been well purified may also contain contaminants, including mercury and dioxins.