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

While cod liver oil is a type of fish oil, what is commonly called “fish oil” comes from different sources.

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

This article will describe the differences between cod liver oil and fish oil. It will list the benefits and risks of each, and give ways a person can include them in their diet, through food or supplements.

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

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

A person must get these acids from the diet; the body does not make them. ALA converts to EPA and then DHA, but the conversion rate is low. To get optimal Omega-3 benefits, a person must take DHA and EPA.

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

  • Differing vitamins: Cod liver oil contains vitamins A and D.
  • Omega-3 content: Cod liver oil comes from the liver of the codfish, which is less fatty than other fish, like tuna and mackerel. For that reason, cod liver oil offers a lower dose of omega-3s.
  • Other health benefits: In addition to the purported benefits of omega-3s, cod liver oil has long been a popular folk remedy for managing constipation and inducing labor.

While cod liver oil is a type of fish oil, people usually use the term “fish oil” to refer to fattier fish oils, such as those from tuna and mackerel.

Some research shows that omega-3s may improve heart health by lowering blood pressure or reducing the risk of a heart attack. Most such research has focused on populations that have a lot of fish oil in their diet, not people who supplement with fish oil.

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

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

Researchers continue to study omega-3s for a wide range of conditions, but the data so far is inconclusive. For example, a 2019 meta-analysis of omega-3s suggests they may improve symptoms of depression, but other studies have been inconclusive or undermined this claim.

Like other fish oils, cod liver oil may reduce the risk of some medical conditions. A 2014 cohort study that followed a group of people who supplemented with cod liver oil and a group who did not found a lower risk of heart health conditions in the group that took cod liver oil.

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

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

Some other research also hints at the health benefits of cod liver oil. A 2011 study emphasizes that, because it is a source of both omega-3s and vitamin A, cod liver oil may 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, may offer the following health benefits:

  • reducing the risk of osteoporosis, especially when a person takes it along with calcium
  • lowering the risk of developing certain types of tumors
  • improving the health of the immune system
  • supporting glucose metabolism

Emerging evidence suggests, but does not conclude, that the risk of severe COVID-19 illness is higher in people who do not get enough vitamin D.

Learn more about the benefits of fish oils here.

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

  • Fish allergies: Fish oil supplements may trigger some fish allergies. In some people, the reaction may be severe.
  • Stomach issues: Some people who take fish oil supplements experience stomach issues such as bloating, gas, diarrhea, or constipation.
  • Bad taste: Fish oil can leave a fishy taste in the mouth, and a person might notice bad breath right after taking the supplement.
  • Blood pressure: Limited research suggests that omega-3s might lower blood pressure. People taking blood pressure medication should talk to a doctor before trying these supplements.
  • Blood clotting: Omega-3s might also affect blood clotting, so people with clotting disorders, bleeding disorders, and those taking clotting medication should talk to a doctor before supplementing with fish oil.
  • Interactions with other drugs: Doctors have not identified all possible drug interactions associated with fish oil, so people who take any medication that is vital for their health should talk to a doctor before supplementing.

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


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


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


Capsules with fish oil may be a more palatable option for people who do not want to use oily supplements.


Vegans and vegetarians may not want to eat fish oil. Flax oil contains omega-3s, but not the EPA and DHA in fish oil. Algal oil contains DHA, but not EPA.

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

CategoryRecommended daily
intake in grams (g)
0–12 months0.5 g
1–3 years0.7 g
4–8 years0.9 g
9–13 years1.2 g for males
1 g for females
14 years +1.6 g for males
1.1 g for females
people who are
1.4 g
people who are
1.3 g

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

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

Most research shows that food is the healthier source of fish oil, and that the apparent benefits of omega-3s may be less apparent when a person takes supplements. For example, the cardiovascular benefits of omega-3s may only be present in people who eat omega-3-rich foods, not supplements.

Omega-3s from cod liver oil and fish oil may offer important health benefits, and there is little evidence that they can harm healthy people.

To get the most benefits, consider increasing fish intake. People interested in trying supplements should talk to a doctor first.

For those who do not wish to eat fish products, there are other great sources of omega-3s, such as algal oil.