What’s the Difference Between Cod Liver Oil and Fish Oil?

Fish oil and cod liver oil come from distinct sources, yet both can significantly boost your intake of omega-3 fatty acids. Cod liver oil is derived specifically from the liver of cod, whereas fish oil is extracted from the flesh of various fatty fish species.

Although these supplements are often grouped together, cod liver oil and fish oil are not identical. They originate from different parts of fish and offer slightly different nutritional profiles and advantages. In fact, cod liver oil is considered a specialized form of fish oil due to its unique vitamin content.

The primary health advantages of both fish oil and cod liver oil stem from their rich concentration of omega-3 fatty acids. These essential fats play a vital role in supporting cardiovascular, neurological, and immune function, and may help lower the risk of several chronic conditions. Because the human body cannot produce omega-3 fatty acids on its own, they must be obtained through diet or supplementation.

For individuals exploring supplement combinations and wondering, Can you take cod liver oil and castor oil at the same time?, it’s important to first understand how cod liver oil works in the body. If you’re considering combining oils, you may also want to review Can you take cod liver oil and castor oil together for a deeper look at potential interactions and safety considerations.

The omega-3 fatty acids found in fish oil are eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). These are often referred to as the “good fats” and are widely recognized for their beneficial effects on heart and brain health.

Plant-based foods such as nuts, seeds, and certain vegetable oils contain another omega-3 known as alpha-linolenic acid (ALA). However, ALA has not been shown to provide the same level of benefit as EPA and DHA derived from marine sources.

If you do not consume two to three servings of nonfried fish per week, supplementing with fish oil or cod liver oil may help you meet recommended omega-3 intake levels.

Where do fish oil and cod liver oil come from?

Fish oil is typically obtained from the tissue of oily fish such as:

• herring
• tuna
• anchovies
• mackerel
• salmon

Cod liver oil, as its name suggests, is extracted specifically from the livers of codfish. Atlantic cod and Pacific cod are the species most frequently used in its production.

Fish accumulate omega-3 fatty acids by consuming phytoplankton, which in turn absorb microalgae. Microalgae are the original and primary source of these beneficial omega-3 fatty acids in the marine food chain.

Benefits of cod liver oil

Cod liver oil provides substantial amounts of EPA and DHA, along with vitamins A and D. Many of its potential health benefits are believed to result from its potent anti-inflammatory properties.

Compared to standard fish oil, cod liver oil stands out due to its naturally occurring vitamins A and D, which contribute additional immune and bone-supporting effects.

Cod liver oil may help:

• reduce inflammation throughout the body
• reduce pain associated with arthritis
• ease symptoms of anxiety and depression
• support healthy fetal brain function and vision development
• maintain strong bone density
• lower risks of type 1 diabetes when used during pregnancy and early infancy
• enhance immune system performance
• help prevent upper respiratory illness
• lower triglycerides in the bloodstream
• lower blood pressure
• slightly increase HDL, commonly called “good cholesterol”
• prevent plaque build-up in the arteries

Historically, cod liver oil used to be routinely given to children in the United States to prevent rickets. Over time, however, concerns emerged regarding excessive vitamin intake and potential toxicity.

Benefits of fish oil

Approximately 30 percent of fish oil consists of pure omega-3 fatty acids. Fish oil is particularly beneficial for:

• cardiovascular health
• mental well-being
• conditions linked to inflammation
• pregnancy
• breastfeeding

Fish oil may help:

• support healthy brain development and cognitive performance
• prevent mental health disorders in at-risk individuals and ease symptoms of schizophrenia and bipolar disorder
• reduce waist circumference
• reduce inflammation and pain associated with rheumatoid arthritis
• promote healthy skin
• support pregnancy, fetal growth, and breastfeeding
• support liver health

Are fish oil and cod liver oil safe?

Fish oil and cod liver oil are widely regarded as safe for most individuals, but it is still advisable to consult your doctor before beginning either supplement. As with any dietary supplement, side effects are possible, and certain populations should use caution.

• Always speak with your child’s pediatrician before giving either oil to a child.
• The safety of fish oil or cod liver oil in people with fish or shellfish allergies remains unclear.
• Individuals with heart or blood disorders should exercise caution when using these supplements.

Cod liver oil may:

• lead to belching
• trigger nosebleeds
• cause heartburn
• thin the blood
• contain high levels of vitamins A and D, though this remains debated

Avoid taking cod liver oil if you are pregnant.

Fish oil may cause:

• issues with blood clotting or nosebleeds
• nausea
• loose stools
• skin rash
• indigestion and fish-flavored burps
• decreased vitamin E levels
• interactions with contraceptive medications, weight loss drugs containing orlistat, and blood medications

If you are evaluating supplement combinations and asking, Can you take cod liver oil and castor oil at the same time?, it’s also wise to explore What not to mix with cod liver oil? to minimize the risk of adverse interactions.

How much do you need?

Both fish oil and cod liver oil are available in capsule and liquid formulations. Supplements generally contain lower mercury levels than whole fish.

Determine your dosage based on the concentration of EPA, DHA, and vitamins listed on the supplement label. There is no universally established recommended dose of EPA or DHA, so the appropriate amount varies. Discuss your needs with your doctor, review product labels carefully, and compare EPA and DHA values to those found in whole fish.

For example:

• 3 ounces of wild Atlantic salmon, cooked, provides 1.22 grams of DHA and 0.35 grams of EPA
• 3 ounces of Pacific cod, cooked, provides 0.10 grams of DHA and 0.04 grams of EPA

When using supplements, more is not necessarily better. Excessive intake of omega-3 fatty acids from any source can result in unwanted side effects, including bleeding risks and digestive upset.

You may consult the National Institutes of Health database of dietary supplement labels to evaluate specific brands.

In most cases, it is advisable to choose either fish oil or cod liver oil, rather than taking both simultaneously. Both provide omega-3 fatty acids, but cod liver oil also delivers vitamins A and D. If those additional vitamins are beneficial for you, cod liver oil alone may suffice.

If you prefer to avoid extra vitamins A and D, fish oil alone may be more appropriate. Alternatively, you may pair fish oil with separate vitamin A and D supplements instead of using cod liver oil.

Taking these supplements with meals—particularly those containing dietary fat—can improve digestion and enhance omega-3 absorption.

Never replace a prescribed medication with a supplement without medical supervision.

Where can you buy them?

Fish oil is often more widely available than cod liver oil, although both are easy to find. Today, dietary supplements are accessible in grocery stores, health food shops, and major retailers such as Target and Amazon.

Product quality should be your top priority. Because it can be difficult to judge supplement purity, ask your healthcare provider for a reputable brand and look for products that undergo third-party testing for quality and contaminants.

Store supplements in a cool, dark location, and avoid using them if they develop a rancid odor.

The takeaway

Fish oil and cod liver oil are two popular supplements used to increase omega-3 fatty acid intake. These essential fats are crucial for the optimal function of the heart, brain, immune system, and developing fetus during pregnancy.

While fish oil and cod liver oil share many similarities, their specific benefits and potential risks differ because they come from different parts of the fish and vary in vitamin content. Carefully consider your nutritional needs—and consult a healthcare professional—before deciding which option is best for you.