9 Science-Backed Benefits of Cod Liver Oil

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.

Each teaspoon (tsp), or 5 milliliters (mL), of cod liver oil provides the following (4, 5, 6):

• Calories: 41
• Fat: 4.5 grams (g)
• Omega-3 fatty acids: 890 milligrams
• Monounsaturated fat: 2.1 g
• Saturated fat: 1 g
• Polyunsaturated fat: 1 g
• Vitamin A: 150% of the Daily Value (DV)
• Vitamin D: 56% of the DV

Cod liver oil is incredibly nutritious, with a single teaspoon providing 150% of the DV for vitamin A and 56% of the DV for vitamin D.

Vitamin A has many roles in the body, including maintaining healthy eyes, brain function, and skin (7, 8).

With the high levels of vitamin A in cod liver oil, keep in mind that the upper tolerable levels of vitamin A for adult males and females over 19 are 3,000 micrograms (mcg) retinol activity equivalents (RAE). Each tsp of cod liver oil contains 1350 mcg RAE (5).

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 (9).

Summary

Cod liver oil is very nutritious and provides a good amount of 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 (10).

The omega 3-fatty acids in cod liver oil may reduce chronic inflammation by suppressing the proteins that promote it (11).

Cod liver oil also contains vitamins A and D, which are powerful antioxidants. They can reduce inflammation by binding and neutralizing harmful free radicals (12, 13).

Interestingly, studies also show that people who are deficient in vitamins A and D are at a greater risk of chronic inflammation (14, 15, 16).

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.

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 40. This can lead to fractures later in life, especially after menopause (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 (9).

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 (19, 20).

More clinical and longitudinal studies are needed to better understand the effects of vitamin D on bone density in healthy children (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, as their skin doesn’t get enough sunlight to synthesize vitamin D for many 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 older 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 older study, 43 people took a 1-g capsule of cod liver oil daily for 3 months. They found it reduced symptoms of rheumatoid arthritis, such as morning stiffness, pain, and swelling (24).

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

By the end of the study, 39% of those 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.

5. May support eye health

Vision loss is a huge health problem, affecting over 2.2 billion 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 which can result from chronic inflammation (26).

Some research suggests that omega-3 fatty acids reduce risk factors for glaucoma, such as eye pressure and nerve damage (27, 28).

Furthermore, diets high in vitamin A may reduce the risk of glaucoma and AMD, compared to diets lower in vitamin A (29, 30).

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 (31).

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 AMD.

6. May reduce heart disease risk

Heart disease is the leading cause of death worldwide, affecting over 17.9 million people annually (32).

Studies have shown people who regularly eat fish have a lower risk of heart disease. This effect can be attributed to its omega-3 fatty acid content (33, 34).

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% (2).
• Increasing HDL cholesterol: Omega-3 fatty acids in cod liver oil can raise HDL (good) cholesterol, which is linked to a lower risk of heart disease (35).

While taking fish oil supplements like cod liver oil may reduce risk factors for heart disease, it’s unclear whether it can actually prevent heart disease or stroke (35).

Unfortunately, few studies have specifically examined the association of cod liver oil and heart disease, 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.

7. May improve symptoms of anxiety and depression

Anxiety and depression are common conditions that together affect over 615 million people worldwide (36).

Interestingly, studies suggest there may be a link between chronic inflammation and anxiety and depression (37, 38, 39).

Many studies have found that the omega-3 fatty acids in cod liver oil can lower inflammation and reduce symptoms of anxiety and depression (40, 41).

An older large study in 21,835 people found that those who took cod liver oil regularly had fewer symptoms of depression alone or combined with anxiety (42).

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

Furthermore, other research has turned up mixed results. For instance, one review of nine studies found that omega-3 supplements had no significant effect on reducing symptoms of depression in older adults (43).

Many studies have also found a link between increased blood levels of vitamin D and a reduction in symptoms of depression, but the evidence so far is not very strong. Additional studies are needed (44).

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 (45, 46).

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 (47).

They are often caused by bacterial infections, smoking, excessive use of anti-inflammatory medications, or too much acid in the stomach (47).

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 (48).

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.

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 vitamin D.

A common dose is often 1–2 tsp, but taking up to 1 tablespoon per day is usually safe. Higher doses are not recommended, as they would result in excess vitamin A intake (49).

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

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

Also, people who are pregnant should check with a doctor before taking it, as high levels of vitamin A may cause harm to the baby (50).

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 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 tsp of liquid cod liver oil per day. You can also try the capsule form.

If you struggle with the fishy taste, try taking it with a meal or blending the oil into smoothies or other drinks to help hide the taste and smell.