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Norwegian cod liver oil

Also known as: Cod liver oil, CLO, Norwegian cod liver oil, Omega-3 fatty acid supplement, Gadus morhua liver oil

Overview

Cod liver oil (CLO) is a dietary supplement derived from the liver of cod fish, primarily Gadus morhua. It is a rich natural source of omega-3 fatty acids, specifically eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), along with fat-soluble vitamins A and D. Historically used as a general health tonic, CLO is primarily utilized today for its potential benefits in cardiovascular health, inflammation reduction, and as a source of essential vitamins. While extensive research supports the benefits of omega-3 fatty acids, studies specifically on cod liver oil, though moderate, indicate its efficacy in certain areas. It is available in liquid and capsule forms, and its key characteristics include its high content of EPA, DHA, and vitamins A and D.

Benefits

Cod liver oil offers several evidence-based benefits, primarily due to its omega-3 fatty acid and vitamin content. A significant benefit is its anti-inflammatory action; studies have shown that regular cod liver oil users exhibit significantly lower C-reactive protein (CRP) levels, a marker of inflammation, compared to non-users. This suggests a role in reducing systemic inflammation. Furthermore, marine oils, including cod liver oil, have demonstrated a statistically significant, albeit modest, pain-reducing effect in patients with arthritis, particularly those with rheumatoid arthritis, with an approximate 8% improvement on a Visual Analog Scale (VAS) for pain. While the evidence quality for pain reduction is moderate, it highlights a specific population that may benefit. Secondary effects, such as potential improvements in cardiovascular health and immune function, are also suggested, though more robust evidence specifically for cod liver oil is needed to confirm these broader benefits. The time course for observing benefits can vary, but regular, consistent use is generally required.

How it works

The primary mechanism of action for cod liver oil stems from its high concentration of omega-3 fatty acids, EPA and DHA. These fatty acids act through anti-inflammatory pathways by modulating the production of eicosanoids, which are signaling molecules derived from fatty acids. Specifically, EPA and DHA compete with arachidonic acid (an omega-6 fatty acid) for metabolism by cyclooxygenase (COX) and lipoxygenase (LOX) enzymes, leading to the production of less inflammatory eicosanoids. This shift in eicosanoid balance helps to regulate cytokine production and reduce overall inflammation. Cod liver oil interacts with various body systems, including the cardiovascular, immune, and nervous systems, by influencing lipid metabolism and inflammatory responses. It is generally well-absorbed, particularly when consumed with dietary fat, which enhances its bioavailability.

Side effects

Cod liver oil is generally considered safe for most adults when taken at recommended dosages. The most common side effects, affecting more than 5% of users, include gastrointestinal upset such as nausea, indigestion, or diarrhea, and a characteristic fishy aftertaste or burps. Uncommon side effects, occurring in 1-5% of individuals, may include allergic reactions in sensitive individuals and an increased risk of bleeding, especially at higher doses, due to the anti-platelet effects of omega-3s. Rare side effects, less than 1%, primarily involve vitamin A toxicity, which can occur with excessive intake due to the high vitamin A content in cod liver oil; symptoms can include headache, dizziness, and liver damage. Cod liver oil may interact with certain medications, notably anticoagulants and blood thinners, increasing the risk of bleeding. High doses are contraindicated in pregnancy due to the potential for vitamin A toxicity, which can be teratogenic; pregnant women should consult a healthcare provider before use. Individuals with fish allergies should avoid cod liver oil.

Dosage

The minimum effective dose of cod liver oil typically aims to provide 1-2 grams of combined EPA and DHA per day. Optimal dosage ranges vary depending on the specific health goal; for anti-inflammatory effects, dosages providing 1-3 grams of combined EPA and DHA daily are often suggested. It is crucial not to exceed 3 grams of combined EPA and DHA per day without medical supervision, as higher doses can increase the risk of side effects, particularly bleeding. Cod liver oil is best taken with meals, as dietary fat enhances the absorption and bioavailability of its fat-soluble components, including omega-3s and vitamins A and D. Both liquid and capsule forms are available, and consumers should choose high-quality products that are tested for purity and minimal contaminants. While no specific cofactors are strictly required, vitamin E is sometimes added to cod liver oil products to help stabilize the omega-3 fatty acids and prevent oxidation.

FAQs

Is cod liver oil safe to take daily?

Yes, cod liver oil is generally safe for daily use for most adults within recommended dosages. However, consult a healthcare provider if you are pregnant, breastfeeding, or taking blood-thinning medications.

When is the best time to take cod liver oil?

It is best to take cod liver oil with meals. This enhances the absorption of its fat-soluble vitamins and omega-3 fatty acids and can help reduce the likelihood of gastrointestinal upset or a fishy aftertaste.

How long does it take to see benefits from cod liver oil?

The time to observe benefits can vary depending on the individual and the condition being addressed. Some individuals may notice improvements within a few weeks, while others may require several months of consistent use.

Can cod liver oil interact with other medications?

Yes, cod liver oil can interact with certain medications, particularly anticoagulants and blood thinners, due to its omega-3 content, which can increase the risk of bleeding. Always consult your doctor if you are on medication.

What are the main differences between cod liver oil and regular fish oil?

Cod liver oil is specifically from cod liver and naturally contains vitamins A and D in addition to omega-3s. Regular fish oil typically comes from the flesh of various fatty fish and primarily provides omega-3s, with minimal or no vitamins A and D.

Research Sources

https://pmc.ncbi.nlm.nih.gov/articles/PMC8240263/ – This study investigated the relationship between cod liver oil consumption and inflammation markers. It found that individuals who regularly consumed cod liver oil exhibited significantly lower levels of C-reactive protein (CRP), a key indicator of systemic inflammation, compared to non-users. The findings suggest a potential anti-inflammatory benefit of cod liver oil.
https://pmc.ncbi.nlm.nih.gov/articles/PMC5295086/ – This systematic review and meta-analysis evaluated the efficacy of marine oils, including cod liver oil, in reducing pain in arthritis patients. The review concluded that marine oils have a statistically significant, albeit modest, pain-reducing effect, particularly in individuals with rheumatoid arthritis. The evidence quality was moderate, highlighting a specific therapeutic role.
https://www.ous-research.no/no/corona/Projects/21222 – This source describes an ongoing research project in Norway investigating the potential of cod liver oil to prevent COVID-19 and other acute respiratory infections. The study aims to provide insights into the broader immune-modulating effects of cod liver oil beyond its established benefits for inflammation and cardiovascular health.
https://journals.sagepub.com/doi/10.1177/2050312116666216 – This article discusses the pain-reducing effects of marine oils in arthritis patients, specifically mentioning an approximate 8% improvement on a VAS scale. It supports the findings of the systematic review regarding the modest but significant impact of these oils on pain management in arthritic conditions.