How to Choose: Cod Liver Oil vs Fish Oil

Image of cod liver oil capsules on a white background with wording cod liver oil vs fish oil how to choose by The Healthy RD

Cod liver oil is a type of fish oil, so they are very similar. When choosing cod liver oil vs fish oil, however, you should consider your own unique needs as we will discuss in this post.

There are several factors that help make you a savvy consumer of these products. In this post, learn about the differences between cod liver oil and fish oil and how to choose.

Related post: The List of Seed Oils You Should Be Avoiding Now

Cod liver oil vs fish oil overview

Traditionally, people supplemented cod liver oils and fish oil as nutritional supplements for children and adults alike. Surprisingly this supplementation started long ago by the ancient Romans and was used by Hippocrates.

Both cod liver and fish oil may protect the heart because the nutrients found in both help to decrease inflammation. They both may help keep excessive blood clotting in check too. But there are some key differences between most cod liver oil and fish oil supplements on the market today that we will review next.

What is cod liver oil?

Cod liver oil is a type of fish oil that is an extract of oil from the liver of codfish. The benefits of cod liver oil are due to its rich nutrient and omega-3 fatty acid content. For example, cod liver oil is rich in vitamin A which is a critical nutrient for immune function and skin health. However, you will notice that cod liver oils vary a lot by how much vitamin A they contain.

Another important nutrient found in cod liver oil is called vitamin D. Most people living in northern climates or who stay indoors most of the time do not get enough vitamin D, so supplementing cod liver oil can help improve your vitamin D intake.

Because cod liver oil is an extract of the liver from codfish, it can also contain various antioxidants and also has natural phospholipids like choline. The difference between cod liver oil and fish oil in regards to essential fatty acids is that cod liver oil is typically higher in DHA than EPA while purified fish oils are often higher in EPA than cod liver oil.

Last but not least, cod liver oil contains omega-3 fats in the form that is best suited for absorption called triglycerides. This means that cod liver oil is easily absorbed compared to many kinds of fish oils on the market.

What is fish oil?

Fish oil is a type of supplement that can come from any kind of fish, including cod liver, and has many different forms. Most fish oils on the market are highly purified types of omega-3 fats. Adding high-quality fish oil to your diet is a great way to get more healthy omega-3 fats for many people.

Most people should eat more fresh fish regularly in their diets but often fall short. You need to eat about 3 ounces of salmon per day to equal the number of grams of omega 3’s in a single cod liver or fish oil supplement too. In other words, most people need more omega-3 fats for health than their diets provide.

Unlike cod liver oil, fish oil comes in many forms and some are much better for absorption than others. If you choose fish oil, you should choose fish oil in its triglyceride form so that your body absorbs it better. Many fish oils on the market today are in ester form, which is not as effective as triglyceride forms.

Because fish oil is so purified, it does not contain any vitamins or minerals. It often contains natural preservatives to help protect it from oxidation.

Cod liver oil nutrition facts

If you’ve picked up bottles of cod liver oil in the store, you have probably noticed there is a lot of variety in the number of nutrients that each bottle contains. This is because the serving sizes vary by bottle and also because the number of nutrients that each cod liver oil contains can vary.

Omega 3 fats in cod liver oil are important to its overall benefits. It contains both DHA and EPA. The omega-3 fats in cod liver oil are essential fatty acids that help the body in so many ways. 

  • Docosahexaenoic acid (DHA) is often referred to as the brain omega-3
  • Eicosapentaenoic acid (EPA) is known as the anti-inflammatory omega-3 fatty acid

Cod liver oil contains high amounts of both DHA and EPA, so this is why it helps both the body and the mind. Typically it contains a ratio of higher amounts of DHA than EPA, so this is why cod liver oil is thought to be important in brain development.

For example, a teaspoon (5 ml) of cod liver oil, such as Nordic Naturals brand, contains 550 mg of DHA and 340 mg of EPA with 210 mg of another omega-3 fat. This is a high omega-3 cod liver oil. 

In contrast, fish oil is typically higher in EPA than cod liver oil and lower in DHA than cod liver oil.

Benefits of cod liver oil: high vitamin A content

The active vitamin A from cod liver oil is a potent antioxidant.  

In its active form called retinol, vitamin A is critical for a healthy immune system, healing skin tissue, eye health, memory, regulating genes, and heart health.

A good cod liver oil contains between 1000-5000 IU of vitamin A per teaspoon, or around 20-100% of the RDI for brands like Carlson or Garden of Life Icelandic Cod Liver Oil. For reference, the tolerable upper limit of vitamin A is 10,000 IU (3,000 mcg) per day. 

This is important because vitamin A levels are low for more people than most people realize due to a variety of genes that control beta-carotene absorption. This causes inefficient vitamin A metabolism. 

Also, vitamin A from cod liver oil is absorbed well: around 70-90% of vitamin A from cod liver oil is absorbed into your bloodstream. In contrast, only 3% of plant forms of vitamin A, such as carrots, are absorbed, on average. Read more on this topic in the Pros and Cons of Veganism.

When you also consider that most people avoid eating vitamin A-rich foods like liver, the case for taking cod liver oil vs fish oil becomes even stronger.

People eating a high-protein diet also have higher vitamin A requirements. 

Vitamin D in cod liver fish oil

It’s no secret by now that almost everyone is low in vitamin D. One of the best natural food sources of vitamin D on the planet is cod liver oil. 

However, don’t rely solely on cod liver oil for vitamin D deficiency.  Make sure to check your blood levels of vitamin D regularly. 

But cod liver oil can be helpful because it typically contains around 200 to 400 IU of vitamin D per teaspoon.  

What about pollutants and contaminants in cod liver oil?

A concern about cod liver oil and fish oil alike is that they might contain toxins like persistent organic pollutants or mercury.

This can be an issue due to the water quality where the fish live.  

However, toxins aren’t a concern in high-quality cod liver oil supplements and fish oil supplements due to improved purification methods. 

Fish oil vs cod liver oil: when is fish oil best? 

There are two big differences between cod liver oil and omega-3 supplements:

  1. Omega 3 fish oil supplements typically don’t have any vitamins while cod liver oil does
  2. Fish oil is extracted from many different types of fish, such as salmon oil, herring, sardines, and krill. Whereas cod liver oil is from codfish alone.

There are some instances when it is best to choose omega-3 fish oil supplements instead of cod liver oil supplements. 

For example, research clearly supports that fish oil helps to reduce blood pressure levels. Less research has been done using cod liver oil for blood pressure than for purified omega-3 fish oils. 

Keep in mind, that cod liver oil’s omega-3 content may be less than fish oil, but it is better absorbed than most purified fish oils. 

Additionally, if you answer yes to the following questions, you should consider taking fish oil instead of cod liver oil:

  • Do you take a multivitamin that contains more than 50% of the daily value of retinyl palmitate or retinol?
  • Do you take a separate vitamin A supplement made of retinol or retinyl palmitate?
  • Is your primary goal for taking omega 3’s to reduce triglyceride levels or reduce cholesterol?
  • Are you pregnant and already taking a prenatal vitamin with more than 50% of the daily value for retinol or retinyl palmitate?
  • Do you take Accutane?

You can still take cod liver oil to help improve your triglycerides, but sometimes your doctor or healthcare provider will recommend a high dose of omega-3. If you take a high dose of cod liver oil, this may put you in danger of getting too much vitamin A. 

Cod liver oil vs fish oil vs krill oil infographic by The Healthy RD

How to choose a high-quality fish oil

If you choose to take a concentrated fish oil supplement, you should look for a pharmaceutical-grade brand like Nordic Naturals or Vital Nutrients. Also, look for fish oil supplements that are in triglyceride form instead of esther form whenever possible.

Many fish oil supplements contain preservatives because it is highly purified. They are often preserved with vitamin E.

Make sure to avoid fish oil that contains synthetic vitamin E and make sure it contains natural tocopherols instead, like the brands I mentioned above. 

Which is better: krill oil or fish oil? 

Krill oil is a special kind of fish oil derived from krill, which are tiny, oily fish that tend to be healthier than regular fish oil. 

This is because the fat may absorb better than most types of fish oil because it is in the form of phospholipids instead of triglycerides. 

Also, krill oil is rich in an antioxidant called astaxanthin, which is linked to all kinds of improved health. 

That said, krill oil usually contains much less total omega-3 fats than other kinds of fish oil and it is often more expensive. 

Still, at a much lower dose, krill oil has the same cholesterol-lowering effects as fish oil. 

So, krill oil is a better choice than fish oil if you don’t like taking a big pill. 

And the astaxanthin from krill oil may reduce harmful cholesterol as well. 

Choosing a high-quality krill oil like Schiff Mega Red or Dr. Mercola Antarctic Krill Oil is a natural source of antioxidants like astaxanthin, which are good for eye health. 

Tip: regardless of the type of fish oil you choose, make sure it is from a sustainable source as well.

Which is better: krill oil or cod liver oil? 

No studies have ever directly compared the effects of cod liver oil compared to krill oil.  

But, krill oil and cod liver do have one thing in common: both have phospholipids in them, which means they both absorb better than typical fish oil brands according to one study. 

Both contain antioxidants too, albeit different ones: 

Tip: both krill oil and cod liver oil are superior to most fish oils because they absorb better and have more antioxidants.  

You could try switching back and forth between krill oil and cod liver oil to optimize your antioxidant intake or take low doses daily of both. 

Timing of omega-3 supplements and doses

You can take cod liver oil, krill oil, or fish oil at any time of the day, but for the best tolerance, taking it with food is a good idea. 

Taking small doses twice a day is a great option too if you are new to taking fish capsules or liquids. 

The dose you need depends on the reason you are using it, but typically, one to two gelcaps a day of fish oil or 1 teaspoon of cod liver oil, or 1 gelcap of cod liver oil is recommended. 

Make sure to avoid fish oil or cod liver oil if you are allergic to fish or seafood. 

Reasons to take cod liver oil, krill oil, and fish oils

Research studies consistently demonstrate that getting more omega-3 fatty acids in the diet benefits all aspects of health. 

A recent study projects that by optimizing omega 3 levels for people by simply supplementing omega 3’s, we would save $1.7 billion dollars in hospital costs per year alone.    

Not only would we save money that way, but we would also save money in countless other ways.  

Here are some potential preventive uses for cod and/or fish oils as part of a healthy routine:

  • Joint pain
  • Hormone health
  • Anxiety
  • Depression
  • Mood disorders like bipolar disorder and schizophrenia
  • Heart health
  • Congestive heart failure
  • Angina
  • Coronary artery disease
  • Seizures
  • Healthy skin
  • Eczema
  • Psoriasis
  • Reduced wrinkles
  • Asthma
  • Diabetes
  • Eye Health
  • Brain development
  • Dental Health
  • Autoimmune disorders
  • Lupus
  • Multiple sclerosis
  • Rheumatoid arthritis
  • Colitis
  • Immune health
  • Alzheimer’s dementia

Omega 3 fats are essential fatty acids and almost everyone can stand to get more of them in their diet. 

Tip: When considering cod liver oil vs fish oil for these conditions, remember that cod liver oil and krill oil contains anti-inflammatory vitamins while purified fish oil does not. 

Frequently asked questions

Is cod liver oil the same as fish oil?

No.  Cod liver oil is more nutritious than fish oil. It is extracted from the liver of cod, while fish oil can come from miscellaneous sources. Fish oil is a much more processed oil. The difference between fish oil and cod liver oil is clear as outlined above. 

How long does it take cod liver oil to work? 

It can take several weeks for cod liver oil to feel or see its benefits.  The benefits you will feel will also depend on the quality of your diet, so you should always focus on eating highly nutritious and minimally processed foods for them to work their best. 

Is cod liver oil omega 3?

Yes.  Cod liver oil is rich in omega-3 fatty acids that have numerous health benefits. 

Are there any cod liver oil side effects?

Not many.  Omega 3 fats are essential to the diet, so unless you are allergic to cod, you shouldn’t have any side effects from taking cod liver oil.  However, some people experience heartburn or indigestion if they take large doses. To minimize this, start with a small dose. 

When to take cod liver oil capsules? morning or night?

You can take cod liver capsules or fish oil capsules whenever it fits best into your routine. Some people do better if they take small doses several times a day.  This can minimize any fish burps or upset stomachs. 

Can you combine fish oil and cod liver oil?

Yes.  Taking both fish oil and cod liver oil can optimize the amount of omega-3 fats you get in your diet.  Just make sure to follow the dosing instructions on the label and discuss taking these supplements with your healthcare provider before making any changes to your supplement routine. 

Which is better: cod liver oil or omega-3 for arthritis?

Research shows that cod liver oil and purified omega-3 supplements are helpful for both Rheumatoid arthritis and osteoarthritis. When comparing cod liver vs fish oil, however, cod liver oil is better absorbed and has more nutrients.  This means it may help joint health more. Further research is needed to confirm this. 

Are there cod liver oil benefits for men?

Absolutely.  Its anti-inflammatory benefits help men and women alike with many aspects of health as outlined above.  Additionally, research shows that cod liver oil may reduce frailty as men and women age. 

Cod liver oil may also help the body make testosterone, although more research is needed in this area [R]. 

Are there cod liver oil benefits for women?

Yes.  In fact, vitamin A from cod liver oil may lessen the severity of heavy menstrual periods and support hormonal health in women.  

For example, cod liver oil may increase the body’s natural production of estrogen and progesterone, although more research is needed to confirm this. 

How common is vitamin A toxicity from cod liver oil?

There is some controversy about taking cod liver oil because it may raise your vitamin A levels to toxic levels. 

It’s possible to get too much vitamin A, but does this concern happen in real life? 

Rarely. In fact, less than 10 cases of vitamin A toxicity occur per year, according to research. As long as you eat less than 10,000 IU per day of vitamin A (the tolerable upper limit), you won’t get too much. 

In fact, you would have to eat two to five times the recommended serving of codfish oil to exceed the RDI. 

This tolerable upper limit gives a range of safety around it as well, and according to data from the National Health and Examination Survey,  a third of Americans don’t even meet the bare minimum estimated average requirements. 

To learn more about vitamin A, visit Weston Price.


Taking fish supplements has a long tradition of supporting heart health and reducing the risk of chronic diseases. Studies show that taking fish oil and cod liver oil is beneficial for many people. 

When deciding between cod liver oil vs fish oil, remember that cod liver oils and krill oils contain more antioxidants and are better absorbed than most types of fish oil supplements. 

Still, there are reasons some people should avoid cod liver oil and choose a fish oil supplement or a krill oil supplement instead.  This is true if you are already taking supplements that already contain vitamin A in retinol form. 

The information on this website has not been evaluated by the Food & Drug Administration or any other medical body and is shared for educational purposes only. While The Healthy RD’s posts are backed by research, you are unique, so you must seek care from your own dietitian or healthcare provider. This post is not meant to diagnose or treat any conditions. Consult your doctor or healthcare provider before making changes to your supplement regimen or lifestyle.

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