Cod liver oil and fish oil are two different health supplements. They come from different fish sources and have unique benefits. Generally speaking, though, cod liver oil is a specific type of fish oil.

The health benefits of both fish oil and cod liver oil come from their high levels of omega-3 fatty acids. Omega-3 fatty acids support many body systems and may prevent a number of ailments. The human body can’t make its own omega-3 fatty acids, which is why you need to get them in your diet.

The fatty acids in fish oil are eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). These omega-3 fatty acids are the “good oils” that everyone needs to include in their diet.

Some plant sources (such as nuts, seeds, and vegetable oil) contain another kind of omega-3 fatty acid, alpha-linolenic acid (ALA), but it hasn’t been proven to be as beneficial as the fatty acids from fish oils.

If you don’t eat two to three servings of (nonfried) fish per week, you may benefit from taking fish oil or cod liver oil supplements.

Where do fish oil and cod liver oil come from?

Fish oil is usually extracted from the flesh of fatty fish like:

  • herring
  • tuna
  • anchovies
  • mackerel
  • salmon

Cod liver oil, as the name implies, comes right from the livers of codfishes. Atlantic cod and Pacific cod are most commonly used to make cod liver oil.

The fish get their omega-3 fatty acids by eating phytoplankton, which eat microalgae. Microalgae is the original source of rich omega-3 fatty acids.

Benefits of cod liver oil

Cod liver oil contains high levels of EPA and DHA as well as vitamins A and D. Many of the benefits of cod liver oil are believed to be from its powerful anti-inflammatory properties.

The unique strengths of cod liver oil versus fish oil are likely due to the presence of vitamins A and D.

Cod liver oil may help:

Cod liver oil used to be a very common supplement given to children in the United States, especially to prevent rickets, until the practice raised concerns about potential vitamin toxicity.

Benefits of fish oil

Thirty percent of fish oil is pure omega-3 fatty acids. Fish oil is especially helpful in areas of:

  • heart health
  • mental health
  • inflammatory ailments
  • pregnancy
  • breastfeeding

Fish oil may help:

Are fish oil and cod liver oil safe?

Both fish oil and cod liver oil are generally considered safe, but you should still talk with your doctor before taking them. Both fish oil and cod liver oil might cause minor side effects, and they may not be safe for all people:

  • Especially talk with your child’s pediatrician before administering either oil to your child.
  • It’s unknown if fish oil or cod liver oil are safe for people with fish and shellfish allergies.
  • People with heart and blood conditions should be cautious about taking either fish oil or cod liver oil.

Cod liver oil may:

  • cause belching
  • cause nosebleeds
  • cause heartburn
  • make blood thinner
  • contain unhealthy levels of vitamins A and D, although this is still debated
Don’t take cod liver oil while pregnant.

Fish oil may cause:

  • trouble with blood clotting or nosebleeds
  • nausea
  • loose stool
  • rash
  • indigestion and fish-tasting burps
  • reduced vitamin E levels
  • interactions with contraceptive medication, weight loss drugs containing orlistat, and blood medications

How much do you need?

Fish oil and cod liver oil supplements come in capsule and liquid forms. Supplements usually contain less mercury than fresh fish.

Calculate your fish oil and cod liver oil dosage based on the amount of EPA, DHA, and vitamins in fish oil or cod liver oil. There is no standard recommended dosage of EPA or DHA, so you can determine the right dose for you by talking with your doctor, reading supplement bottle labels, and comparing the EPA and DHA levels to what you might get if you ate a whole fish.

For example:

When it comes to supplements, more of a good thing isn’t always better. Too much omega-3 fatty acids in any form can have risky side effects. The National Institutes of Health has a database of dietary supplement labels if you want to research a particular brand.

It’s likely best to take only fish oil or cod liver oil, but not both together. Both oils deliver the benefits from omega-3 fatty acids, but cod liver oil has the added vitamins A and D. If you want those extra vitamins, you can take just cod liver oil.

If you don’t want those extra vitamins, take just the fish oil. You can also take fish oil in addition to vitamin A and D supplements if you want the benefits from those vitamins but don’t want to take cod liver oil.

Taking fish oil or cod liver oil with food, especially fatty food, may help you better digest and absorb the omega-3 fatty acids.

Never switch from a prescription medicine to a supplement without the help and oversight of your doctor.

Where can you buy them?

Fish oil may be easier to find than cod liver oil. However, dietary supplements are becoming easier to find in general. Everywhere from grocery stores to health food stores to Target and Amazon you can find a variety of supplements for sale.

Quality is most important when selecting supplements, and it can be hard to tell which are best. Ask your doctor for a trusted brand and research third-party testing to ensure you buy pure supplements of high quality.

Always keep supplements in a cool, dark place, and never consume them if they smell rancid.

The takeaway

Fish oil and cod liver oil are two supplements you can take to increase your omega-3 fatty acid intake. These fatty acids are essential for healthy functioning of most body systems including the heart, brain, and developing fetuses in pregnancy.

Fish oil and cod liver oil have many of the same attributes, but their specific risks and benefits differ because they come from different sources.