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Evidence Based

9 Science-Backed Benefits of Cod Liver Oil

Cod liver oil is a type of fish oil supplement.

Like regular fish oil, it's high in omega-3 fatty acids, which are linked to many health benefits, including reduced inflammation and lower blood pressure (1, 2).

It also contains vitamins A and D, both of which provide many other health benefits.

Here are 9 scientifically supported benefits of cod liver oil.

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1. High in Vitamins A and D

Most cod liver oil is extracted from the liver of Atlantic cod.

Cod liver oil has been used for centuries to relieve joint pain and treat rickets, a disease that causes fragile bones in children (3).

Although cod liver oil is a fish oil supplement, it's quite different than regular fish oil.

Regular fish oil is extracted from the tissue of oily fish like tuna, herring, anchovies and mackerel, while cod liver oil is extracted from the livers of cod.

The liver is rich in fat-soluble vitamins like vitamins A and D, which give it an impressive nutrient profile.

One teaspoon (5 ml) of cod liver oil provides the following (4):

  • Calories: 40
  • Fat: 4.5 grams
  • Omega-3 fatty acids: 890 mg
  • Monounsaturated fat: 2.1 grams
  • Saturated fat: 1 gram
  • Polyunsaturated fat: 1 gram
  • Vitamin A: 90% of the RDI
  • Vitamin D: 113% of the RDI

Cod liver oil is incredibly nutritious, with a single teaspoon providing 90% of your daily requirements for vitamin A and 113% of your daily requirements for vitamin D.

Vitamin A has many roles in the body, including maintaining healthy eyes, brain function and skin (5, 6).

Cod liver oil is also one of the best food sources of vitamin D, which has an important role in maintaining healthy bones by regulating calcium absorption (7).

Summary: Cod liver oil is very nutritious and provides nearly all of your daily requirements for vitamins A and D.

2. May Reduce Inflammation

Inflammation is a natural process that helps the body fight infections and heal injuries.

Unfortunately, in some cases, inflammation can continue at a low level for long periods of time.

This is known as chronic inflammation, which is harmful and may increase the risk high blood pressure and several diseases, such as heart disease (8, 9, 10).

The omega 3-fatty acids in cod liver oil may reduce chronic inflammation by suppressing the proteins that promote it. These include TNF-α, IL-1 and IL-6 (1).

Cod liver oil also contains vitamins A and D, which are powerful antioxidants. They can reduce inflammation by binding and neutralizing harmful free radicals (11, 12).

Interestingly, studies also show that people who are deficient in vitamins A and D are at a greater risk of chronic inflammation (13, 14, 15).

Summary: The omega-3 fatty acids in cod liver oil may help suppress proteins that promote chronic inflammation. Cod liver oil is also a great source of vitamins A and D, both of which have antioxidant properties.
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3. May Improve Bone Health

It's incredibly important to maintain healthy bones as you age.

This is because you start losing bone mass after age 30. This can lead to fractures later in life, especially in women after menopause (16, 17, 18).

Cod liver oil is a great dietary source of vitamin D and may reduce age-related bone loss. That's because it helps your body absorb calcium, which is a necessary mineral for strong bones, from the gut (7, 19).

In fact, studies show that when accompanied by a diet high in calcium, taking a vitamin D supplement like cod liver oil can reduce bone loss among adults and strengthen fragile bones in children (20, 21, 22).

Getting enough vitamin D from foods and supplements like cod liver oil is especially important for people who live far from the equator, a their skin doesn't get enough sunlight to synthesize vitamin D for up to six months of the year (23).

Summary: Cod liver oil is rich in vitamin D, which helps with maintaining strong and healthy bones. It is especially important for people who live far from the equator.

4. May Reduce Joint Pain and Improve Rheumatoid Arthritis Symptoms

Rheumatoid arthritis is an autoimmune disease that's characterized by damage to the joints.

There is currently no cure for rheumatoid arthritis, but studies suggest that cod liver oil may reduce joint pain and improve symptoms of rheumatoid arthritis like joint stiffness and swelling (24, 25).

In one study, 43 people took a 1-gram capsule of cod liver oil daily for three months. They found it reduced symptoms of rheumatoid arthritis, such as morning stiffness, pain and swelling (24).

In another study in 58 individuals, researchers investigated if taking cod liver oil would reduce pain from rheumatoid arthritis enough to help patients reduce their use of anti-inflammatory medications.

By the end of the study, 39% of people who took cod liver oil comfortably reduced their use of anti-inflammatory medication by over 30% (25).

It is believed that the omega-3 fatty acids in cod liver oil may help reduce inflammation in the joints and protect against damage (24).

Summary: Thanks to cod liver oil's ability to reduce inflammation, it may help reduce joint pain in those who suffer from rheumatoid arthritis.
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5. May Support Eye Health

Vision loss is a huge health problem, affecting over 285 million people worldwide (26).

There are many reasons why people lose their vision, but two of the leading causes are glaucoma and age-related macular degeneration (AMD).

Both of these diseases can result from chronic inflammation.

However, the omega-3 fatty acids and vitamin A in cod liver oil have been shown to protect against eye diseases caused by inflammation (6, 27).

Studies in animals have found that omega-3 fatty acids reduce risk factors for glaucoma, such as eye pressure and nerve damage (28, 29, 30).

In another study in 666 people, researchers found those who ate the most omega-3 fatty acids had a 17% lower risk of early AMD and 41% lower risk of late AMD (27).

Furthermore, diets high in vitamin A may reduce the risk of glaucoma and AMD, compared to diets lower in vitamin A (31, 32).

In one study in 3,502 people aged 55 and over, researchers found that people who consumed the most vitamin A had a much lower risk of glaucoma than those who ate the least vitamin A (6).

Although vitamin A is great for eye health, it's not recommended to take high doses of it, as it may cause vitamin A toxicity.

Summary: Cod liver oil is a great source of omega-3 and vitamin A, both of which may protect against vision loss from inflammatory eye diseases like glaucoma and age-related macular degeneration (AMD).
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6. May Reduce Heart Disease Risk

Heart disease is the leading cause of death worldwide, affecting over 17.5 million people annually (33).

Studies have shown people who regularly eat fish have a much lower risk of heart disease. This effect can be attributed to its omega-3 fatty acid content (34, 35).

Omega-3s have been shown to have many benefits for your heart, including:

  • Reducing triglycerides: Omega-3 fatty acids in cod liver oil may reduce blood triglycerides by 15–30% (36, 37, 38).
  • Lowering blood pressure: Many studies have found that omega-3 fatty acids may lower blood pressure, especially in people with high blood pressure and high cholesterol (2, 39).
  • Increasing HDL cholesterol: Omega-3 fatty acids in cod liver oil can raise good HDL cholesterol, which is linked to a lower risk of heart disease (40, 41).
  • Preventing plaque formation: Animal studies have found that cod liver oil may reduce the risk of plaques forming in the arteries. Plaque buildup can narrow the arteries and lead to a heart attack or stroke (42, 43).

While taking fish oil supplements like cod liver oil may reduce risk factors for heart disease, there is little evidence that it can prevent heart disease or strokes (44).

Unfortunately, few studies have specifically examined the association of cod liver oil and heart diseas, as many studies classify cod liver oil as regular fish oil.

Thus, more specific research on cod liver oil and heart disease risk factors are needed to make a clear link between the two.

Summary: Cod liver oil may help reduce risk factors for heart disease. Studies specifically on cod liver oil and heart disease risk factors are needed, as most studies group cod liver oil with regular fish oils.
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7. May Improve Symptoms of Anxiety and Depression

Anxiety and depression are common illnesses that together affect over 615 million people worldwide (45).

Interestingly, studies suggest there may be a link between chronic inflammation and anxiety and depression (46, 47) Many studies have found that the omega-3 fatty acids in cod liver oil can lower inflammation and reduce symptoms of anxiety and depression (48, 49).

A large study including 21,835 individuals found that people who took cod liver oil regularly had fewer symptoms of depression alone or combined with anxiety (50).

Nevertheless, while omega-3 fatty acids help reduce symptoms of anxiety and depression, their overall effect seems small.

In an analysis of 26 studies including 1,478 individuals, omega-3 supplements were only slightly more effective than placebos at reducing symptoms of depression and anxiety (51).

Moreover, many studies have also found a link between increased blood levels of vitamin D and a reduction in symptoms of depression (52, 53).

How it reduces symptoms of depression is still unclear, but some studies suggest that vitamin D can bind to receptors in the brain and stimulate the release of mood-improving hormones like serotonin (53, 54, 55).

Summary: The omega-3 fatty acids and vitamin D in cod liver oil may help reduce symptoms of anxiety and depression, but more studies are needed.

8. May Help Heal Stomach and Gut Ulcers

Ulcers are small breaks in the lining of the stomach or gut. They may cause symptoms of nausea, upper abdominal pain and discomfort.

They are often caused by bacterial infections, smoking, excess use of anti-inflammatory medications or too much acid in the stomach (56).

Animal studies indicate that cod liver oil may help treat ulcers, particularly in the stomach and gut.

In one animal study, researchers found that low and high doses of cod liver oil helped heal ulcers in both the stomach and gut (57).

Another animal study found that cod liver oil suppressed genes that are linked with gut inflammation and reduced inflammation and ulceration in the gut (58).

While the use of cod liver oil to help heal ulcers seems promising, more studies in humans are needed to make clear recommendations.

Summary: Cod liver oil may help treat ulcers in the stomach and gut, but more human studies are needed before making recommendations.
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9. Easy to Add to Your Diet

Cod liver oil is incredibly easy to add to your diet. It comes in many forms, but liquid and capsule forms are the most common.

There are no set guidelines for cod liver oil intake, so most recommendations are based on safe intake levels of omega-3 fatty acids, vitamin A and D.

A common dose is often 1–2 teaspoons, but taking up to one tablespoon per day is usually safe. Higher doses are not recommended, as they would result in excess vitamin A intake (52).

Although cod liver oil is extremely healthy, some people need to be cautious about their intake since cod liver oil can act as a blood thinner.

So check with your doctor before taking cod liver oil if you take blood pressure or blood thinning medications.

Also, pregnant women should check with their doctor before taking it, as high levels of vitamin A may cause harm to the baby.

Summary: Cod liver oil is easy to add to your diet. Stick with recommended amounts, as excess cod liver oil may be harmful.

The Bottom Line

Cod liver oil is an incredibly nutritious type of fish oil supplement. It's very convenient and contains a great combination of omega-3 fatty acids, vitamin A and vitamin D.

Cod liver oil may provide you with health benefits like stronger bones, reduced inflammation and less joint pain for those with rheumatoid arthritis.

If you want to try supplementing, a common dose is 1–2 teaspoons of liquid cod liver oil per day. You can also try the capsule form.

If you struggle with the fishy taste of either, try taking it on an empty stomach before your first meal or with a few sips of water.

An evidence-based article from our experts at Authority Nutrition.
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