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Diet & Nutrition, Health

Cod Liver Oil vs Fish Oil: Which Is Better?

Registered Dietitian
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Omega-3 fatty acids have so many benefits, such as a reduced risk of cardiovascular disease, type 1 diabetes, certain types of cancer, glaucoma, and stroke. This nutrient is essential for the body’s function, but our bodies are unable to produce them on their own. Therefore, it’s important that we get enough Omega-3 fatty acids from outside sources.

If you’re looking for a way to get your Omega-3 fatty acids in, there are so many ways to do so. If introducing Omega-3s into your diet by eating two to three servings of fish per week doesn’t seem feasible, supplements such as cod liver oil and fish oil are here to help.

Many people use these supplements to boost their health and prevent chronic diseases. In fact, research from the National Institutes of Health showed that, in 2012, 7.8% of adults in the United States and 1.1% of children had taken a fish oil supplement in the previous 30 days.[1]

In this article, I’ll answer the commonly asked question: cod liver oil vs fish oil: which is better? We’ll look at the overall health benefits you can expect from taking Omega-3 supplements and break down the differences between cod liver oil and fish oil.

Facts About Omega-3 Supplements

There are three types of Omega-3 fatty acids: Eicosapentaenoic acid (EPA), Docosahexaenoic acid (DHA), and Alpha-linolenic acid (ALA). EPA and DHA come mainly from fish while ALA comes mainly from plant sources such as flaxseed and walnuts.[2] Omega-3 supplements such as Cod Liver Oil and Fish Oil provide the EPA and DHA our bodies need.

Omega-3 fatty acids are very important for our heart health. They can reduce the risk of cardiovascular disease and blood clots.[3] They can also help to reduce high blood pressure, which is common among adults in the United States.[4]


Omega-3 supplements can also help to reduce high cholesterol and plaque formation in your arteries.[5][6] They can also help to reduce the risk of sudden cardiac death, which occurs when the heart is either pumping irregularly or ineffectively, making it unable to pump blood as intended to the rest of your vital organs.[7]

One important thing to note is that while getting your Omega-3 fatty acids from dietary sources such as fatty fish provides these benefits, studies have shown that taking Omega-3s in the form of supplements does not reduce the risk of heart disease.[8]

Omega-3 fatty acids have non-cardiac benefits as well. Studies show that they can reduce your risk of glaucoma, certain cancers, and certain mental health disorders.[9][10][11]

Some studies also show that including Omega-3 fatty acids in your lifestyle may lead to improved weight loss when combined with a healthful diet.[12]

With all of these possible benefits, it’s understandable why you would want to increase your Omega-3 intakes. If eating fatty fish, such as tuna or salmon, or plant sources of Omega-3s, such as nuts and seeds, consistently doesn’t seem realistic for your lifestyle, you’d likely be interested in taking an Omega-3 supplement. But which supplement is right for you? Let’s explore the benefits of each.


Are These Supplements Safe?

According to the National Institutes of Health, side effects experienced by users of Omega-3 supplements, if any, are usually mild. These side effects may include unpleasant taste, bad breath, headache, and gastrointestinal symptoms. This could include symptoms such as nausea, diarrhea, or heartburn.[13]

Another thing to note with Omega-3 supplements is that they may interfere with medicines that many Americans take to prevent blood clotting. If you’re on one of these medications or if you have a seafood allergy, it’s important to speak with your doctor before deciding to start taking Omega-3 supplements.

While many consumers may be worried about the mercury content of fish oils, a literature review conducted showed that fish oil capsules do not contain mercury. They noted that when the oil is extracted from the fish, the mercury and other heavy metals that may be present actually stay behind.[14]

How Much Should I Take?

The tricky thing about these supplements is that there is no standard recommended dosage for EPA or DHA. It’s recommended that you read the supplement label and only take the recommended dosage. Especially if you choose to take Cod Liver Oil, it’s important to follow the recommended dosage on the supplement’s label as too much Vitamin A can be toxic.

Regardless of which supplement you’re taking, you can also speak with your primary care doctor to determine what dosage is right for you. If you want to research a particular brand of Omega-3 supplement, you can use the Dietary Supplement Label Database from the National Institutes of Health.[15]

Cod Liver Oil vs Fish Oil Benefits

Here are the differences in the benefits between consuming cod liver oil vs fish oil.

Cod Liver Oil Benefits

Cod Liver Oil was often used at the turn of the 20th century to treat rickets, a bone disease caused by Vitamin D deficiency. This is because Cod Liver Oil contains Vitamin D.[16] Cod Liver Oils tested tended to provide about 400 IU of Vitamin D. The recommended daily intake of Vitamin D for adults is 600 IU, so these supplements provide the majority of what you need.[17]

Getting enough Vitamin D through diet or supplements is especially important for individuals who don’t get a lot of sunlight during the day or don’t already get enough Vitamin D from their diet alone. Additionally, Cod Liver Oil contains Vitamin A, which is important for eye health and immune function.


One important thing to note is that Vitamin A can be toxic in high amounts, so when taking Cod Liver Oil, it’s important to stick to the recommended dosage. Cod Liver Oil also has other possible benefits. It’s long been a popular folk remedy for inducing labor and managing constipation.[18]

Fish Oil Benefits

As opposed to Cod Liver Oil, which is a specific type of fish oil, the commonly called “Fish Oil” supplement is a bit different. Fish Oil supplements typically contain oil that has been extracted from fatty fish, such as herring, tuna, or anchovies.[19]

While Fish Oil also contains Omega-3s and, therefore, has similar benefits to Cod Liver Oil supplements, it has one primary benefit: the fish used in these supplements are fattier than Cod. Therefore, Fish Oil supplements have a higher Omega-3 content.[20] This may mean that taking Fish Oil supplements, as opposed to Cod Liver Oil supplements, may end up giving you a bigger bang for your buck.

Cod Liver Oil vs Fish Oil: Which Is Better?

Both Cod Liver Oil and Fish Oil supplements provide the benefits of Omega-3 fatty acids without having to increase your weekly intake of fatty fishes. They both may provide a reduced risk of glaucoma, improved heart health, and reduced risk of mental health disorders and certain types of cancers.

If you’re looking for a supplement that gets the most bang for your buck, Fish Oil supplements may be right for you. They contain a higher level of Omega-3 supplements than Cod Liver Oil supplements, which may end up being more cost-effective for some consumers.


However, if you have a diet low in Vitamin D or Vitamin A or don’t get enough sunlight during the day, it may be helpful to take an Omega-3 supplement that also contains these vitamins. In that case, Cod Liver Oil may be right for you. One of the drawbacks of this supplement, however, is that it does contain lower levels of Omega-3 than Fish Oil supplements do.

As noted, if you are on blood thinners or have a seafood allergy, it’s important to speak with your doctor before starting any of these supplements.

Whichever supplement you choose, know that these supplements have overall very mild possible side effects and can be a great addition to a healthful diet to promote overall wellness.

Featured photo credit: Caroline Attwood via cod liver oil vs fish oil


[1]NIH: Omega-3 Supplements: In-Depth
[2]Harvard School of Public Health: Omega-3 Fatty Acids: An Essential Contribution
[3]Cleveland Clinic: Omega-3 Fatty Acids
[4]PubMed.gov: Moderate consumption of fatty fish reduces diastolic blood pressure in overweight and obese European young adults during energy restriction
[5]ResearchGate: Omega-3 fatty acids in health and disease and growth and development
[6]PubMed.gov: Effect of omega-3 fatty acids supplementation on endothelial function: a meta-analysis of randomized controlled trials
[7]Mayo Clinic: Ventricular fibrillation
[8]NCCIH: Omega-3 Supplements: In-Depth
[9]TVST: Oral Omega-3 Supplementation Lowers Intraocular Pressure in Normotensive Adults
[10]PubMed.gov: Dietary fatty acids and colorectal cancer: a case-control study
[11]PubMed.gov: Long-chain omega-3 fatty acids for indicated prevention of psychotic disorders: a randomized, placebo-controlled trial
[12]PubMed.gov: Randomized trial of weight-loss-diets for young adults varying in fish and fish oil content
[13]NCCIH: Omega-3 Supplements: In-Depth
[14]Anabolic Labs: Fish oil supplementation: Evidence for health benefits
[15]National Institutes of Health: Dietary Supplement Label Database (DSLD)
[16]PubMed.gov: Vitamin D, cod-liver oil, sunlight, and rickets: a historical perspective
[17]ConsumerLab: What is the difference between fish oil and cod liver oil? Is one better than the other?
[18]NCBI: What Started Your Labor? Responses From Mothers in the Third Pregnancy, Infection, and Nutrition Study
[19]Healthline: What’s the Difference Between Cod Liver Oil and Fish Oil?
[20]Medical News Today: What are the differences between cod liver oil and fish oil?
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