COD Liver Oil Vs. Fish Oil Capsules

Omega-3 is an essential fatty acid known for its heart benefits, which include a reduction in blood triglyceride levels, a more regular heart beat, lowered inflammation and decreased formation of atherosclerotic plaques. Cod liver oil and fish oil capsules are good options for people who are not willing to eat at least two weekly servings of fish, as recommended by the American Heart Association. However, they are not suitable if you suffer from fish or seafood allergies, as they can cause allergic reactions.

Close-up of a fish oil capsule in someone's hand. Credit: Zoonar RF/Zoonar/Getty Images

Manufacturing of Cod Liver Oil Vs. Fish Oil Capsules

The manufacturing process of cod liver oil and fish oil is different. Cod liver oil is made from the oil of the liver of cod fish, hence its name. Cod livers are steamed and then pressed to extract the oil. Cod liver oil is available in liquid or capsules. On the other hand, fish oil capsules are made of the flesh of different types of fish -- such as salmon, herring or sardine -- which is then pressed to extract the oil. The extracted fish oil is available in capsules.

Types of Omega-3 in Cod Liver Oil Vs. Fish Oil Capsules

The types of omega-3 found in cod live oil and fish oil capsules are the same. They both contain docosahexaenoic acid, or DHA, and eicosapentaenoic acid, or EPA, which are marine sources of omega-3, in similar proportions. There is a third type of omega-3, called alpha-linolenic acid, or ALA, which is found in some vegetable products such as flaxseeds, walnuts, canola and soybean oil. DHA and EPA, both found in either cod liver oil and fish oil capsules, reduce the risk of coronary heart disease and iscemic stroke, explains the Linus Pauling Institute.

Extra Vitamins in Cod Liver Oil Vs. Fish Oil Capsules

The main difference between cod liver oil and fish oil capsules is that cod liver oil contains the fat-soluble vitamins A and D. Because these vitamins are stored in the liver of the fish, they are found in cod liver oil, but not in fish oil capsules. Fat-soluble vitamins can cause toxicity in excessive amounts. The tolerable upper limit intake, or UL, for adults is set at 2,000 IU for vitamin D and 3,000 IU for vitamin A. Above this UL, vitamin D can lead to nausea, vomiting, weakness and constipation, while vitamin A may induce birth defects, liver problems, osteoporosis and even central nervous system disorders.

Contaminants in Cod Liver Oil Vs. Fish Oil Capsules

Another big difference between cod liver oil and fish oil capsules is their degree of contamination with pollutants. The liver has many roles, including filtering different substances in the body. For this reason, cod liver oil may contain more environmental contaminants, such as polychlorinated biphenyls, or PCBs, compared to other fish oil capsules. Fish oil capsules are relatively safe in regards to contaminants because methylmercury and PCBs tend to accumulate in the flesh of the fish rather than in its oil. Keep in mind that young children, pregnant women and nursing women are more vulnerable to heavy metals and should therefore consult their doctors to discuss any concerns.

Cod Liver Oil Vs. Fish Oil Capsules in Pregnancy

Because cod liver oil contain high levels of vitamins A and D and is more likely to contain PCBs and other contaminants, pregnant women should avoid taking it. Consuming too much vitamin A during pregnancy can cause a number of birth defects, including malformation of the eyes, heart and skull. Fish oil capsules are safer during pregnancy; they provide the same omega-3, without the risk of overdosing on fat-soluble vitamins or harming the fetus with contaminants.


Americans consume on average 0.1 to 0.2mg of EPA and DHA, the more potent types of omega-3. The World Health Organization recommends 0.3 to 0.5mg of EPA and DHA combined daily, whether it comes from the consumption of fresh fish or supplements like cod liver oil or fish oil capsules. If you are interested in taking fish oil supplements, talk to your doctor or pharmacist to determine the proper dosage as omega-3 interacts with some medications, especially blood thinners such as warfarin and clopidogrel, among others.

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