Cod Liver Oil vs. Fish Oil: What’s the Difference, and Which Should You Take?

If you’re considering taking an omega-3 supplement, you have a few different options. Two of the most common options include fish oil and cod liver oil. Both come from fish. But they aren’t the same thing.

In terms of cod liver oil versus fish oil, how can you tell them apart? Let’s take a look at some of their differences (and similarities).

Is cod liver oil the same as fish oil?

Cod liver oil is a type of fish oil. But cod liver oil and fish oil come from different sources, and they have slightly different nutrient profiles. 

Cod liver oil comes from the liver of cod fish. Fish oil comes from the skin and muscle of many different types of fatty fish, such as:

• Anchovy

• Herring

• Mackerel 

• Sardine

• Capelin

• Menhaden

• Salmon

• Tuna

Both cod liver and fish oil supplements provide omega-3 fatty acids. Omega-3s are beneficial dietary fats that have many functions in your body, including:

• Building and maintaining healthy cells

• Helping to regulate the levels of fats in your blood

• Controlling body-wide inflammation

There are three main types of omega-3 fatty acids:

1. Eicosapentaenoic acid (EPA) 

2. Docosahexaenoic acid (DHA)

3. Alpha-linolenic acid (ALA)

Both cod liver oil and fish oil contain the first two types, EPA and DHA. These are better absorbed by the body than the third type, ALA. Cod liver oil and fish oil don’t contain ALA.

EXPERT PICKS: WHAT TO READ NEXT

• What’s the healthiest fish to eat? All fish is high in protein and low in saturated fat. But the most nutritious fish — like salmon and sardines — are also high in beneficial omega-3 fatty acids.

• Fish oil vs. eating fish: Fish and fish oil supplements both have omega-3 fats. But it’s better to get this nutrient through food when possible. 

• Foods with vitamin D: Vitamin D supports your immune, heart, and bone health. Fatty fish, egg yolks, and liver are among the few foods that naturally contain it.

You can usually find cod liver oil and fish oil supplements in tablet, liquid, or gummy form. 

Cod liver oil benefits

The main thing that sets cod liver apart from fish oil is its vitamin content. In addition to its omega-3 fatty acids, cod liver oil contains a high amount of vitamins D and A. That’s because these vitamins are stored in the liver. Some cod liver supplements provide as much as 50% or more of the daily value for each of these vitamins. However, the exact amount varies by brand. 

Cod liver oil is one of the most concentrated sources of vitamin D. Vitamin D has many important roles in the body, including:

• Helping calcium absorption

• Supporting strong bones and teeth

• Strengthening the immune system

The vitamin A in cod liver oil helps keep your heart, lungs, and eyes healthy. But it’s important to note that too much vitamin A can be harmful. It’s best not to consume more than 1 tsp of cod liver oil per day. This is the standard dose. The exact amount of vitamin A in cod liver oil varies by brand. But sometimes there’s as much as 1,350 mcg of vitamin A in each dose of cod liver oil. This exceeds your daily needs.

The Recommended Dietary Allowance (RDA) for vitamin A is:

• Men: 900 mcg retinol activity equivalents (RAE) 

• Women: 700 mcg RAE for adult women

• Pregnant people: 800 mcg RAE for pregnant people

The maximum recommended amount (Tolerable Upper Intake Level, or UL) for daily vitamin A is 3,000 mcg.

Fish oil benefits

Fish oil is the most common non-vitamin or mineral supplement in the U.S. And more research is available on fish oil than on cod liver oil. 

Studies on fish oil have found that its omega-3s may help: 

• Support healthy blood pressure levels 

• Lower triglycerides, a type of fat in your blood that can increase risk of heart disease

• Improve memory

• Reduce joint pain (when studied in people with rheumatoid arthritis)

• Improve mood (when studied in people with postpartum depression)

And taking fish oil during pregnancy may have benefits for the infant, including:

• Improving immune function

• Reducing the risk of severe eczema

• Reducing the risk of food sensitivities

• Lowering the chance of developing asthma 

Are cod liver oil and fish oil safe?

Side effects of cod liver and fish oil supplements are generally mild, but they can include: 

• Bad breath, or having an unpleasant taste in the mouth

• Headache 

• Fishy body odor 

• Nausea

• Heartburn

• Loose stools

Less common side effects of cod liver specifically include:

• Vitamin D toxicity

• Vitamin A toxicity

It’s also important to note that the omega-3 fats in cod liver oil and fish oil can prevent blood from clotting. This is often considered a benefit, since this lowers your risk of blood clots. 

But high doses of omega-3s can also increase your risk of bleeding, especially if you’re also taking blood thinners or other medications that affect blood clotting. 

Usually, “high doses” means over 2,000 mg per day. This is more than the recommended daily dose (250 mg to 500 mg per day for most people). But some people with certain health conditions may benefit from higher doses. This is why it’s a good idea to talk to your healthcare team before starting cod liver oil or fish oil. Your primary care provider can help figure out if these supplements are a safe option for you. 

Is cod liver oil safe during pregnancy?

Not all health experts agree on whether cod liver is safe during pregnancy. But some health organizations advise against taking cod liver oil (and other supplements with vitamin A) in pregnancy. This is because too much vitamin A may be harmful to the fetus. 

Which is healthier, cod liver oil or fish oil?

Whether you choose cod liver oil or fish oil as a source of omega-3s might depend on your personal health goals. 

As an example, people who are at higher risk for vitamin D deficiency may be better off choosing cod liver oil over fish oil supplements. On the other hand, if you already take other supplements containing vitamins A or D, you may be better off taking a fish oil supplement. 

But most experts recommend getting omega-3s from your diet rather than from supplements when possible. 

Foods that contain omega-3s include:

• Fatty fish like salmon and tuna

• Flaxseed and chia seeds 

• Walnuts 

• Tofu

• Edamame

• Avocado

• Spinach

• Kidney beans

• Soy milk

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Written by:

Joanna Foley, RD

Joanna Foley, RD, is a registered dietitian (RD) and the owner of joannafoleynutrition.com, a private nutrition consulting business. She has previously worked as a clinical dietitian and outpatient renal dietitian.

Edited by:

Meredith Hoffa

Meredith Hoffa is a senior health editor at GoodRx, where she leads journalists and clinicians covering various well-being topics, particularly in diet and nutrition.

Reviewed by:

Katie E. Golden, MD

Katie E. Golden, MD, is a board-certified emergency medicine physician and a medical editor at GoodRx.

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