Omega 3, cod liver oil and fish oil – key differences

by Hannah de Gruchy April 23, 2023

Omega 3, cod liver oil and fish oil – key differences

Omega 3, cod liver oil and fish oils are all common food supplements that share many benefits yet have subtle differences.

All three are good sources of anti-inflammatory omega-3 fatty acids. These are essential nutrients that we need to obtain from our diet or from supplements and they are important for our overall health. Cod liver oil and fish oils contain additional vitamins, but a lower concentration of omega 3 than pure omega 3 supplements.

Oily fish are a good dietary source of omega 3, but unless we’re eating one or two portions a week, we may not be getting enough to meet our needs. Supplementing our diet with either an omega 3 capsule, a cod liver oil or a fish oil supplement is therefore beneficial.

Omega 3, cod liver oil and fish oils: Fast facts

  • Omega-3 fatty acids are essential polyunsaturated fats that we need to include in our diet for our overall health.
  • Cod liver oil and fish oils contain omega 3, to varying degrees.
  • Cod liver oil also contains vitamins A and D and some fish oil supplements contain vitamin E, but both tend to have a lower concentration of omega 3 than pure omega 3 supplements.
  • To gain the most benefit, take an omega-3 supplement, rather than cod liver oil or fish oils, alongside a high-quality multivitamin if you need extra nutritional support.

What is omega 3?

walnuts, linseeds and chia seeds

Omega 3 is a type of polyunsaturated, healthy, or ‘good’ fat that we need for various aspects of our health, in particular the health of our heart and brain. The body cannot manufacture these essential fatty acids by itself, so for this reason we ought to consume omega 3 in our diet.

There are three main types of omega-3 fatty acids - EPA (eicosapentaenoic acid), DHA (docosahexaenoic acid), and ALA (alpha-linolenic acid). EPA and DHA are found mainly in oily fish (or the livers of non-oily fish) while ALA is found in plant-based foods that are rich in good fats such as walnuts, linseeds, and chia seeds.

The body uses EPA and DHA for many biological functions, but ALA is only used minimally for energy. Processes during digestion can convert ALA into EPA and DHA, but the process is very inefficient.

If you don’t consume fish or fish-derived supplements, it’s best not to rely on plant-based ALA-rich foods as you may become deficient in omega 3. Instead, opt for an omega-3 supplement made using ocean algae. Ocean algae are high in EPA and DHA – and this is where the fish get their own omega 3 from, so by taking an algae supplement, you’re cutting out the middle fish!

Benefits of omega 3

Omega 3 plays an essential role in a healthy heart and circulatory system. It does this by helping to regulate levels of harmful fats called triglycerides in the blood, and by raising levels of HDL, or good, cholesterol. There’s also evidence that it helps to prevent blood clots, which can lead to cardiovascular disease. 

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Metabolic syndrome is a term used to describe a series of health conditions that can coexist together, including obesity, high blood triglycerides, LDL (bad) cholesterol, and high blood sugar. Having metabolic syndrome puts an individual at risk of developing heart disease and type 2 diabetes. Evidence suggests that taking omega-3 supplements could help to improve the metabolic status of overweight individuals.

Studies have also found that omega-3 fatty acids help to reduce our risk of developing depression and may help to alleviate the symptoms or severity of anxiety. Further, studies suggest that those with a higher intake of omega 3 (either through diet or supplementation) have a decreased rate of mental decline as they age and a reduced risk of developing Alzheimer’s’ disease.

Developmentally, omega 3 is important for the normal growth and development of the brain in babies and young children, allowing for better cognition, communication and social skills, and a reduced risk of developmental delays and behavioural problems.

Finally, omega 3 has anti-inflammatory properties and it’s known that supplements play a role in reducing chronic inflammation. Chronic inflammation increases our risk of developing diseases such as heart disease, type 2 diabetes, dementia, and certain cancers. Eating a healthy, balanced diet rich in omega 3, or taking an omega-3 supplement, can therefore help to reduce this risk.

What is cod liver oil?

As its name suggests, cod liver oil supplements are derived from the liver of the cod fish, most commonly from the Atlantic or Pacific cod. Since it’s derived from the oily liver of a fish, it contains omega-3 fatty acids. However, because it’s derived from the liver, rather than the fatty tissues, cod liver oil tends to contain lower concentrations of omega 3 than pure omega 3 supplements. 

Cod liver oil supplements are naturally rich in vitamins A and D, both fat-soluble vitamins that are stored in the liver, and that are not found in omega-3 supplements. 

The benefits of cod liver oil 

Cod liver oil

The omega 3 benefits of cod liver oil are the same as for omega 3 supplements, they just might be less beneficial due to the lower concentrations.

However, cod liver oil does have added benefits, from vitamins A and D. Vitamin A is essential for healthy eyes and eyesight and can protect against age-related macular degeneration that can reduce our vision. It also has an anti-inflammatory effect on the body.

Manufactured by the body when UV light from the sun reaches our skin, vitamin D is essential for healthy teeth and bones, as well as to support our emotional health. It’s thought that most adults become deficient in vitamin D during the autumn and winter months when they’re exposed to fewer sunlight hours.

What are fish oils?

Unlike cod liver oil, that’s derived from a certain part of a certain species of fish, fish oil supplements are made using the fatty flesh of a variety of oily fish including tuna, salmon, herring, mackerel, and pilchards.

Like cod liver oil, fish oils are rich in omega 3 fatty acids (but again to a lesser extent than omega 3 supplements), however, they don’t contain vitamins A and D. Some fish oil supplements contain vitamin E. 

The benefits of fish oils

As with cod liver oil, fish oil supplements provide the same benefits as omega 3 supplements, just potentially to a lesser extent due to a lower concentration. Vitamin E is an antioxidant vitamin essential for the health and vitality of the skin and joints.

How do I take these supplements?

There is no strict recommended daily intake of omega-3 fatty acids but always look for supplements that contain high-grade ingredients. Always follow the advice on the individual packaging regarding the daily intake. They’re usually best taken with food.

Are there any side effects?

If you have an allergy to fish or shellfish, avoid taking any fish-derived supplements. Some people experience bloating and stomach discomfort when they first start taking omega 3, cod liver oil or fish oils. If you experience this, reduce your daily intake, or take them every other day for a few weeks to get used to them.

Some people experience an aftertaste from taking these supplements or develop “fishy burps”. If so, you could try taking algae-based omega-3 supplements instead. A pregnant woman should avoid taking vitamin A supplements and it’s therefore not advisable to take cod liver oil whilst pregnant or trying to become pregnant. If you’re taking medications for blood clotting disorders, speak to your GP before taking any supplement containing omega 3.

Which one is best for me? 

Given that omega 3 supplements tend to contain higher levels of EPA and DHA, perhaps the best option is to choose an omega 3 supplement, alongside a multivitamin that contains vitamins A, D and E if you feel you need to supplement your diet further. Vegan Multi from G&G Vitamins is a good choice.


Omega 3 fish oil - G&G
Omega 3 fish oil softgels from G&G Vitamins contain high-grade EPA and DHA from small, wild-caught fish and are independently tested for purity. Best taken with a meal that contains healthy fats to aid absorption, they’re free from gluten, sugar, lactose, soya, and GMOs and contain no artificial fillers or binders.

G&G Vitamins also offer Children’s fish oil softgels that contain a lower dose of EPA and DHA, ideally suited to younger members of the family. This supplement is also manufactured from high-grade, wild-caught fish and contains no allergens or fillers.

Whichever supplement you choose, it’s important to read the label to ensure that you’re getting the nutrients you think you’re getting. Although we’ve mentioned here that cod liver oil tends to contain vitamins A and D, and fish oils may contain vitamin E, this may not always be the case. Read the labels carefully if you’re relying on supplements to provide more than omega 3 alone.

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Hannah de Gruchy
Hannah de Gruchy


Health and wellness author and biologist specialised in sustainability, nutrition and eco-living.

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