Cod liver oil is a liquid fat extracted from the fresh liver of the Atlantic cod (Gadus morhua).
The beneficial effects of cod liver oil are mainly based on its nutrients:
In studies, omega-3 fatty acid supplements reduced inflammation by achieving the following:
- Improved cell membrane function
- Decreased cytokines (substances immune cells produce that may increase inflammation)
Vitamin D is important for bone health. It elevates levels of the following in the body:
These minerals are necessary for bone mineralization. Vitamin D also plays a vital role in immune system regulation.
Vitamin A plays a crucial role in the correct functioning of multiple body processes, including the following:
- Cell growth
- Skin health
Read on for more information about cod liver oil’s uses and benefits.
Cod Liver Oil Supplement Facts
- Active Ingredient(s): Two forms of omega-3 polyunsaturated fatty acids, EPA and DHA, as well as vitamin D and vitamin A
- Legal Status: Over-the-counter (OTC) dietary supplement (United States)
- Suggested Dose: May vary based on age and dosage form
- Safety Considerations: Cod liver oil is safe to use during pregnancy when approved by a healthcare provider and in children over the age of 1 year old. It is recommended that children take half the recommended adult dose at most. It is important to monitor the overall intake of vitamin A when taking cod liver oil.
Uses of Cod Liver Oil
Due to its high levels of omega-3 fatty acids such as EPA and DHA, as well as its high levels of vitamin A and vitamin D, cod liver oil has shown modest evidence for the following uses.
Reducing Overall Inflammation
In a small study among athletes competing in the North Sea Race, supplementation with cod liver oil specifically—as opposed to other omega-3 supplements—reduced the presence of inflammatory cytokines circulating in the athletes’ blood after the race.
It is hypothesized that the combined effects of the EPA and DHA omega-3 fatty acids in the cod liver oil supplements, along with their levels of vitamins D and A, contributed to this decreased inflammation.
Additionally, in a group of pregnant people with gestational diabetes, supplementation with cod liver oil reduced several markers of inflammation, including cytokines and insulin resistance.
Improved Childhood Health Outcomes
Daily supplementation of cod liver oil for children is common in Nordic countries, as is supplementation during pregnancy.
One study showed that cod liver oil supplementation during pregnancy and infancy decreased asthma development risk among school-age children.
Additionally, a Norwegian trial showed an association between cod liver oil supplementation during adolescence and a decreased risk of lifetime development of multiple sclerosis.
This decrease was hypothesized to be an effect of the high vitamin D levels available through cod liver oil.
Improved Heart Health Measurements
In an analysis from the United Kingdom, low doses of omega-3 fatty acids from cod liver oil supplementation were observed to lower the risk of death due to cardiovascular (heart and blood vessel) issues.
This may be due to omega-3 fatty acids’ effects on heart rate and arrhythmia.
Among pregnant people, supplementation with cod liver oil showed an overall decrease in several lipid panel measures:
- Total cholesterol
- Triglycerides (a type of fat in the blood)
- Low-density lipoprotein (LDL) cholesterol (considered “bad” cholesterol)
These lipid measurements are key measures of heart health.
Another 30-day trial showed that subjects treated with a common statin drug and cod liver oil reduced their total cholesterol, LDL cholesterol, and triglyceride levels.
An increase in HDL (“good”) cholesterol levels was also noted.
Some research suggests antibacterial, antiviral, and antifungal effects associated with omega-3 PUFAs.
The fatty acids extracted from cod liver oil have been shown to cause a significant reduction of herpes simplex virus type 1 (HSV-1) activity on the skin. However, how fatty acids act as antiviral agents is unclear.
Additionally, fish liver oil has proved to be an effective antibacterial agent against gram-positive bacteria. There may be emerging uses for cod liver oil extract in antibacterial topical ointments.
There is also increasing interest in the effect of cod liver oil supplementation on bone health for adults over age 65. A study review detected a link between cod liver oil and blood levels of vitamin D in adults over 65.
High blood vitamin D levels may be associated with the following:
- Increased bone mineral density
- Decreased bone loss
- Decreased fracture risk
It appears that this effect is only seen, however, when combined with calcium supplementation.
What Are the Side Effects of Cod Liver Oil?
There are no known side effects from cod liver oil consumption itself.
However, since cod liver oil is high in vitamin A, it is important to know the following signs and symptoms of possible vitamin A toxicity:
- Reduced appetite
- Blurry vision
- Hair loss
- Muscle pain
- Altered mental status
It is also possible to be allergic to any supplement or food.
If you believe that you are having a severe allergic reaction or if any of your symptoms feel life-threatening, call 911 and get medical help right away.
Do keep the following precautions in mind when using cod liver oil:
- Severe allergic reaction: Avoid using cod liver oil if you have a known allergy to it or its ingredients. Ask your pharmacist or healthcare provider for a complete list of the ingredients if you’re unsure.
- Pregnancy: Several different cultures supplement with cod liver oil in pregnancy. However, vitamin A toxicity can affect fetus development. When pregnant, check with your healthcare provider before starting cod liver oil supplementation.
- Breastfeeding: As vitamin A can be transferred to a breastfeeding infant, it is best to first discuss cod liver supplementation with your healthcare provider during breastfeeding.
- Adults over age 65: There is increased interest in the effect of cod liver oil supplementation on bone health for adults over 65. Check with your healthcare provider if supplementation with cod liver oil is right for you.
- Children: Studies recommend no more than 2.5 mg of cod liver oil daily, as the effects of high levels of omega-3 fatty acids on childhood development are unclear. Supplementing any child under the age of 1 with cod liver oil is no longer recommended.
- Other modifications: Do not take cod liver oil if you are already taking a vitamin A supplement, have a diet high in vitamin A, or have any condition that causes high levels of vitamin A in the blood.
Dosage: How Much Cod Liver Oil Should I Take?
Always speak with a healthcare provider before taking a supplement to ensure that the supplement and dosage are appropriate for your individual needs.
For adults, studies from Norway suggest a daily dosage of 5 mg of cod liver oil, as the high latitude of Norway decreases the amount of vitamin D residents can obtain from the sun.
The lower latitude and increased sun exposure in the United States may reduce this recommendation slightly, but no studies have been done to determine an optimal amount.
For children, recent Nordic studies have recommended a reduction in cod liver oil supplementation—from 5 mg to 2.5 mg daily—as the effects of high omega-3 fatty acid levels on children are unclear. Supplementing any child under the age of 1 with cod liver oil is no longer recommended.
Dietary supplements are not regulated the way drugs are in the United States, meaning the Food and Drug Administration (FDA) does not approve them for safety and effectiveness before products are marketed. Choose a supplement tested by a trusted third party, such as the U.S. Pharmacopeia (USP), ConsumerLab.com, or NSF.org, when possible. However, even if supplements are third-party tested, they are not necessarily safe for all or effective in general. Therefore, talking to your healthcare provider about any supplements you plan to take and asking about potential interactions with other supplements or medications is important.
What Happens If I Take Too Much Cod Liver Oil?
Toxicity or overdose of cod liver oil has not been researched and, thus, cannot be determined.
However, cod liver oil contains high vitamin A levels. Be mindful of potential vitamin A toxicity, particularly when combined with other supplements or a diet rich in vitamin A.
The symptoms of vitamin A toxicity are listed in the Side Effects section above.
Do not take cod liver oil and a separate vitamin A supplement to avoid possible vitamin A toxicity.
Discuss with your healthcare provider whether to avoid taking a vitamin D supplement while taking cod liver oil.
It is essential to carefully read a supplement’s ingredients list and nutrition facts panel to know which ingredients and how much of each ingredient is included. Please review the supplement label with your healthcare provider to discuss potential interactions with foods, other supplements, and medications.
Supplements similar to cod liver oil include omega-3 fatty acid supplements from the following origin:
- Vegetarian: from algae oil, chia seeds, flax and hemp seed, seaweed, and walnuts)
- Fish oil
These supplements contain similar levels of omega-3 PUFAs as cod liver oil. However, they do not typically contain vitamins A or D.
Also, there is the question of whether the body can absorb the fatty acids from vegetarian sources as well as it absorbs the fatty acids from fish oil sources.
There is evidence that cod liver oil has particular benefits in decreasing inflammation compared to omega-3 fatty acid supplements.
Additionally, it has been shown that vegetarian omega-3 supplements may contain higher levels of mercury than cod liver oil supplements.
Sources of Cod Liver Oil and What to Look For
Cod liver oil is only found in the extracted liquid fat from the liver of the cod fish.
Whenever possible, try to obtain high-quality cod liver oil from Atlantic cod.
Cod liver oil with higher levels of free fatty acids, as opposed to triglycerides, appears to have more beneficial effects.
Cod liver oil is a liquid fat extracted from the fresh liver of the Atlantic cod (Gadus morhua).
The beneficial effects of cod liver oil are mainly based on its nutrients: two forms of omega- 3 polyunsaturated fatty acids (PUFAs) known as eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), as well as vitamin D and vitamin A.
Cod liver oil is helpful for lipid and heart health, as well as for inflammation.
It is suitable for use during pregnancy when approved by a healthcare provider and in low doses for children over 1 year.
Frequently Asked Questions
What nutrients does cod liver oil contain?
The beneficial effects of cod liver oil are based on several key nutrients: two forms of omega- 3 polyunsaturated fatty acids (PUFAs) known as eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), as well as vitamin D and vitamin A.
Omega-3 fatty acid supplements may reduce inflammation by improving cell membrane function and decreasing pro-inflammatory cytokines. Vitamin D is important for bone health and immunity. Vitamin A plays a key role in the correct functioning of multiple body processes.
What are some of the benefits of taking cod liver oil?
Cod liver oil appears to be useful for reducing lipid levels and promoting overall heart health. It has also been shown to decrease inflammation for both athletes and pregnant individuals.
Finally, it appears to be of emerging interest as both an antimicrobial topical formula and as a promoter of bone health in adults over age 65.
How do I take cod liver oil safely?
To safely take any supplement—including cod liver oil—it is important to inform your healthcare providers about any medication changes or additional herbs or supplements you take.
This can help them prevent possible interactions and side effects. They can also ensure you take cod liver oil at appropriate doses.
It is particularly important to be aware of the signs and symptoms of vitamin A toxicity when taking cod liver oil, as it contains high levels of Vitamin A.