Differences, advantages, types and more



Both cod liver oil and fish oil are oils that come from fish. They are a great source of omega-3 fatty acids, which can reduce the risk of some chronic diseases.

While cod liver oil is a type of fish oil, what is commonly referred to as “fish oil” comes from a variety of sources.

There are some differences between cod liver oil and fish oil. For example, they contain different amounts of omega-3 fatty acids and different vitamins.

This article describes the differences between cod liver oil and fish oil. It lists the benefits and risks of each, and shows ways a person can incorporate them into their diet through food or supplements.

Both cod liver oil and fish oil are sources of omega-3 fatty acids. Omega-3 fatty acids are a group of fatty acids that, in small doses, are important for human health.

Most studies focus on three types of omega-3 fatty acids: alpha-linolenic acid (ALA), docosahexaenoic acid (DHA), and eicosapentaenoic acid (EPA). The benefits of each acid can vary slightly, so all three can improve health.

A person must get these acids from food; the body doesn’t make them. ALA converts to EPA and then to DHA, but the conversion rate is low. For optimal omega-3 benefits, a person must be consuming DHA and EPA.

Cod liver oil is a type of fish oil. The main differences between cod liver oil and other fish oils include:

  • Different vitamins: Cod liver oil contains vitamins A and D.
  • Omega-3 content: Cod liver oil comes from the liver of cod, which is less fat than other fish such as tuna and mackerel. For this reason, cod liver oil offers a lower dose of omega-3 fatty acids.
  • Other health benefits: In addition to the supposed benefits of omega-3 fatty acids, cod liver oil has long been a popular folk remedy for treating constipation and inducing labor.

While cod liver oil is a type of fish oil, people usually use the term “fish oil” to refer to fatter fish oils like tuna and mackerel.

Some research shows that omega-3 fatty acids can improve heart health by lowering blood pressure or reducing the risk of a heart attack. Most of this research has focused on populations who have high levels of fish oil in their diet, not people who supplement with fish oil.

Not all research supports these potential benefits. A 2012 study of people with diabetes found that omega-3 supplements lowered triglyceride levels but did not reduce the risk of a heart attack.

Omega-3 supplements, including fish oil, can also:

Researchers continue to study omega-3 fatty acids for a variety of medical conditions, but the data so far are inconclusive. For example, a 2019 meta-analysis of omega-3s suggests that they can improve symptoms of depression. However, other studies have been inconclusive or have undermined this claim.

Like other fish oils, cod liver oil can reduce the risk of some diseases. A 2014 cohort study that followed a group of people who took cod liver oil and a group that found no lower risk of heart disease in the group who took cod liver oil.

The study also found that cod liver oil users had more health problems and were more likely to report bone disease and benign growths.

The study’s authors suggest that people with health problems may be more likely to use cod liver oil. Additionally, they found that cod liver oil users had healthier lifestyles, suggesting that other differences might explain the different health outcomes between groups.

Some other research points to the health benefits of cod liver oil as well. A 2011 study emphasizes that since cod liver oil contains both omega-3 fatty acids and vitamin A, it can help protect against glaucoma.

Vitamin D plays an important role in health. About a quarter of Americans may be deficient. Cod liver oil is a source of vitamin D and, as such, can provide the following health benefits:

  • Reducing the risk of osteoporosis, especially if a person takes it with calcium
  • Reducing the risk of developing certain types of tumors
  • Improving immune system health
  • Support of the glucose metabolism

New evidence suggests, but does not conclude, that people who are not getting enough vitamin D are at greater risk of developing severe COVID-19.

Find out more about the benefits of fish oils here.

Since both cod liver oil and fish oil are fish oils that contain omega-3 fatty acids, the risks are similar. They include:

  • Fish allergies: Fish oil supplements can trigger some fish allergies. In some people, the reaction can be severe.
  • stomach problems: Some people who take fish oil supplements have stomach problems such as bloating, gas, diarrhea, or constipation.
  • Bathroom taste: Fish oil can leave a fishy taste in the mouth, and a person may notice bad breath immediately after taking the supplement.
  • Blood pressure: Limited research suggests that omega-3 fatty acids may lower blood pressure. People taking blood pressure medication should speak to a doctor before trying these supplements.
  • Blood clotting: Omega-3 fatty acids can also affect blood clotting. Therefore, people with coagulation disorders, bleeding disorders, and those taking coagulation medications should speak to a doctor before supplementing with fish oil.
  • Interactions with other drugs: Doctors have not identified all possible interactions with fish oil. Therefore, individuals taking medications that are vital to their health should speak to a doctor before taking any supplement.

There are three main types of cod liver oil and fish oil supplements:


A person can get cod liver oil by eating cod liver oil. A number of foods, including most fish, are good sources of omega-3 fatty acids and may offer superior benefits over dietary supplements. Fatty fish like tuna and mackerel are highest in omega-3 fatty acids.


A number of manufacturers make pure fish oil formulas or fish oil that includes other supplements. These oils usually contain higher concentrations of fish oil, but they can taste bad.


Fish oil capsules may be a tastier option for people who don’t want to use oily supplements.


Vegans and vegetarians may not want to eat fish oil. Flax oil contains omega-3 fatty acids, but not the EPA and DHA found in fish oil. Algae oil contains DHA but no EPA.

The last Institute of Medicine review to determine the correct dosage of omega-3 fatty acids relied on inconclusive data. Instead, the organization looked at the average intake in healthy groups and recommended the following daily intake:

Eating two to three servings of fish a week can also help a person get the recommended amount of omega-3 fatty acids.

Supplements vary in the amount of omega-3s present, as well as the types of omega-3s. It is important to check the label. Users should look for other ingredients as well, as taking too many supplements can increase the risk of overdosing on a vitamin.

Most research shows that foods are the healthier source of fish oil and that the obvious benefits of omega-3 fatty acids may be less obvious when a person is taking supplements. For example, the cardiovascular benefits of omega-3 fatty acids can only be present in people who eat omega-3 rich foods, not dietary supplements.

Omega-3s from cod liver oil and fish oil can provide important health benefits, and little evidence suggests that they can harm healthy people.

To get the greatest benefits, consider increasing your fish intake. Individuals interested in nutritional supplements should speak to a doctor first.

For those who don’t want to eat fish products, there are other great sources of omega-3 fatty acids like seaweed oil.


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