{"url":"https://whatshealthyandwhy.com/cod-liver-oil/vitamins-and-omega-3","path":"/cod-liver-oil/vitamins-and-omega-3","alternates":{"json":"https://whatshealthyandwhy.com/api/articles/cod-liver-oil/vitamins-and-omega-3.json","markdown":"https://whatshealthyandwhy.com/cod-liver-oil/vitamins-and-omega-3.md"},"topic":{"slug":"cod-liver-oil","name":"Cod Liver Oil","url":"https://whatshealthyandwhy.com/cod-liver-oil"},"slug":"vitamins-and-omega-3","order":1,"title":"Vitamins A, D, and Omega-3 in One Traditional Oil","question":"What does cod liver oil actually do for your health?","answer":"Cod liver oil may help people with rheumatoid arthritis cut NSAID use, but evidence for mood and inflammation benefits is observational.","description":"How cod liver oil delivers a synergistic trio of vitamin A, vitamin D3, and EPA/DHA omega-3s — and why the dose matters","confidence":2,"confidenceNote":"A 97-person RCT in rheumatoid arthritis was positive; the 34,601-person RCT missed its COVID-19 endpoint; mood and CRP findings are observational.","evidenceSummary":{"rctCount":2,"observationalCount":3,"metaAnalysisCount":0,"totalParticipants":"57,000+","replicated":false,"newestStudyYear":2022},"category":{"categoryTitle":"What's Good For You","categorySlug":"good-for-you","subcategoryName":"Foods & Drinks","subcategorySlug":"foods","url":"https://whatshealthyandwhy.com/explore/good-for-you/foods"},"actions":["Standard dose is 1 teaspoon (5 ml) a day: roughly 1,000–2,000 IU vitamin A, 400–1,000 IU vitamin D3 and 1,000–1,500 mg EPA+DHA.","Choose brands that test for and publish contaminant levels (PCBs, dioxins); third-party-tested Norwegian and Icelandic brands are generally highest quality."],"cautions":["Preformed vitamin A accumulates in the liver; chronic intakes above 10,000 IU a day are linked to liver damage, bone loss and birth defects.","Pregnancy: one teaspoon a day keeps vitamin A within safe limits, but discuss any supplement with a healthcare provider.","The arthritis result used 10 g a day alongside usual DMARD therapy, more than the standard teaspoon dose [3]."],"simpleText":"Cod liver oil has been a staple of traditional northern European health practice for centuries — Norwegian and Icelandic fishing communities gave it to children long before anyone understood why it worked. What makes it distinctive from regular fish oil is its source: the liver, which concentrates fat-soluble vitamins alongside the omega-3 fatty acids EPA and DHA. A single teaspoon delivers meaningful amounts of vitamin A (retinol), vitamin D3, and omega-3s together — nutrients that most people are low in and that work synergistically [1][5].\n\nThe catch is that more is not always better. Vitamin A is fat-soluble and accumulates in the body, so getting the dose right matters as much as taking it at all.","mediumText":"What's Inside Cod Liver Oil\n\nThe three main active components all come together in a form the body absorbs readily:\n\nVitamin A (retinol) is the preformed, ready-to-use version — not the beta-carotene found in carrots, which the body must convert. Retinol is directly used for: maintaining the mucosal lining of the respiratory and digestive tracts, supporting night vision, regulating immune cell development (particularly T cells and natural killer cells), and keeping skin and reproductive tissue healthy. A single teaspoon of high-quality cod liver oil typically provides 1,000–2,000 IU (300–600 mcg RAE) of vitamin A.\n\nVitamin D3 in cod liver oil is cholecalciferol — the same form your skin produces in sunlight. Most people in northern latitudes are deficient by winter's end. Vitamin D regulates calcium absorption, influences hundreds of genes involved in immunity and cell growth, and supports mood. A teaspoon of cod liver oil provides roughly 400–1,000 IU of D3 depending on the product.\n\nEPA and DHA are the long-chain omega-3 fatty acids behind cod liver oil's anti-inflammatory effects. EPA (eicosapentaenoic acid) competes with arachidonic acid in the inflammatory pathway, reducing prostaglandin synthesis. DHA (docosahexaenoic acid) is a structural component of brain and retinal cell membranes. Together, they reduce serum triglycerides, support vascular function, and may modulate mood via their role in neuronal membrane fluidity [3][4].\n\nSynergy Between the Three Nutrients\n\nVitamins A and D are interdependent in ways that explain why cod liver oil performs differently from isolated supplements of either nutrient. They share nuclear receptors (RAR and RXR for vitamin A; VDR for vitamin D), and both receptors heterodimerize with RXR — meaning adequate vitamin A is necessary for vitamin D signaling to work properly. Taking large doses of vitamin D without corresponding vitamin A can actually impair immune function rather than support it. Cod liver oil provides them together in ratios that mirror traditional diets.\n\nAnti-inflammatory and Joint Benefits\n\nThe n-3 fatty acids in cod liver oil reduce the production of inflammatory cytokines (IL-1, IL-6, TNF-alpha) and eicosanoids derived from arachidonic acid. In a 9-month randomized double-blind trial of 97 patients with rheumatoid arthritis, those taking 10g of cod liver oil daily (providing 2.2g of n-3 fatty acids) were significantly more likely to be able to reduce or eliminate their daily NSAID use compared to placebo — 39% vs. 10% achieved a clinically significant reduction [3]. This NSAID-sparing effect has real implications: long-term NSAID use carries GI and cardiovascular risks, and reducing dependence on them is clinically meaningful.\n\nIn a prospective study of 1,002 recreational cyclists who took part in a 91 km race, regular omega-3 supplement users had lower basal and exercise-induced C-reactive protein (CRP) levels than non-users, and the effect was present only in regular cod liver oil users, whose exercise-induced CRP response was 24% lower after adjustment [4].\n\nMood and Depression\n\nThe Hordaland Health Study, a population-based cross-sectional study of 21,835 adults in Norway, found that daily cod liver oil use was associated with a 30% lower prevalence of depressive symptoms (2.5% vs. 3.8%) after controlling for confounders including fish consumption and lifestyle factors [2]. The mechanism is thought to involve EPA's role in reducing neuroinflammation and DHA's structural role in neuronal membranes, with vitamin D's influence on serotonin synthesis likely contributing.\n\nImmune and Respiratory Infection\n\nA large Norwegian randomized controlled trial enrolled 34,601 adults during the COVID-19 pandemic (November 2020 to June 2021) to test whether daily cod liver oil supplementation reduced rates of acute respiratory infection [1]. Participants received 5 ml/day of cod liver oil (providing roughly 400 IU vitamin D3). While the trial did not show a statistically significant reduction in COVID-19 specifically, it found a meaningful reduction in other respiratory tract infections and was notable for its scale and rigorous blinding.\n\nDosing and Safety\n\nStandard dosing is 1 teaspoon (5 ml) per day, providing approximately:\n- 1,000–2,000 IU vitamin A\n- 400–1,000 IU vitamin D3\n- 1,000–1,500 mg EPA+DHA combined\n\nThis range is safe for most adults. The concern with cod liver oil is chronic over-supplementation of vitamin A. Preformed retinol accumulates in the liver, and intakes above 10,000 IU/day over time are associated with liver damage, bone density loss, and teratogenicity in pregnancy. At typical 1-teaspoon doses, cod liver oil is safe, but taking multiple supplements containing retinol simultaneously warrants attention.\n\nPregnancy: The vitamin A content is the reason cod liver oil is sometimes flagged during pregnancy. At 1 teaspoon/day, the vitamin A dose is well within safe limits, but as with all supplements, it's worth discussing with a healthcare provider.\n\nQuality matters: Cod livers accumulate fat-soluble toxins from the ocean (PCBs, dioxins) along with the vitamins. Choose products from brands that test for and publish contaminant levels. Norwegian and Icelandic brands with third-party testing are generally highest quality.\n\nSee our Omega-3 page for the broader evidence on EPA and DHA. For vitamin D specifically, see Vitamin D.","deepText":"Evidence Review\n\nBrunvoll et al. (2022) conducted a quadruple-blinded randomized placebo-controlled trial with 34,601 Norwegian adults aged 18–75 during the COVID-19 pandemic. Participants received 5 ml/day of cod liver oil or placebo from November 2020 to June 2021. The primary outcome was SARS-CoV-2 infection confirmed by PCR. While the trial found no statistically significant reduction in COVID-19 specifically (OR 0.82, 95% CI 0.66–1.02), it did find a reduction in symptomatic respiratory infections broadly. The trial is notable for its exceptional scale — among the largest supplement RCTs ever conducted — and its rigorous quadruple-blinding methodology. The absence of effect on COVID-19 may reflect the relatively low vitamin D dose (approximately 400 IU/day from the cod liver oil) and the fact that Norway had high baseline vitamin D intake [1].\n\nRaeder et al. (2007) analyzed data from the Hordaland Health Study, a population-based cross-sectional study of 21,835 adults in Norway. After adjusting for potential confounders including age, sex, smoking, physical activity, income, marital status, and dietary fish intake, daily cod liver oil users had significantly lower prevalence of high depressive symptoms than non-users (2.5% vs. 3.8%, OR 0.66, 95% CI 0.50–0.88). The effect was independent of dietary fish intake, suggesting a contribution from the concentrated EPA/DHA dose or the fat-soluble vitamins in cod liver oil beyond what comes from food. This study design cannot establish causality — people who take cod liver oil may differ in unmeasured ways from those who do not [2].\n\nGalarraga et al. (2008) conducted a 9-month dual-centre, double-blind placebo-controlled RCT in 97 patients with established rheumatoid arthritis. Patients were randomized to 10g/day of cod liver oil (2.2g n-3 EPA+DHA) or placebo capsules, with all patients maintaining their background DMARD therapy. The primary outcome was the ability to reduce NSAID dose by 30% or more while maintaining disease control. Thirty-nine percent of cod liver oil patients achieved this threshold versus 10% of placebo patients (p=0.003). Secondary outcomes including pain VAS score, morning stiffness duration, and Ritchie articular index all trended favorably in the cod liver oil group, though not all reached significance individually. This is one of the most robust clinical demonstrations of cod liver oil's anti-inflammatory efficacy [3].\n\nHansen et al. (2021) conducted a prospective observational study, a 2014 sub-study of the North Sea Race Endurance Exercise Study (NEEDED), in 1,002 healthy recreational athletes who took part in a 91 km bicycle race. CRP was measured before and 24 hours after the race. Of the cohort, 274 reported regular use of omega-3 supplements, and 173 of those used cod liver oil. Regular omega-3 supplement users had significantly lower basal and exercise-induced CRP levels than non-users (p<0.001), with a 27% reduction in the log-transformed CRP response unadjusted and a 16% reduction after adjusting for age, sex, race duration, body mass index, change in creatine kinase, weekly MET hours, resting heart rate and higher education. Cod liver oil was the primary driver of this response, with a 34% reduction unadjusted (95% CI 19–49) and a 24% reduction after adjustment (95% CI 11–38, p<0.001); the effect was present only in regular cod liver oil users. The observational design limits causal inference [4].\n\nEvidence summary: The anti-inflammatory and NSAID-sparing effects in rheumatoid arthritis are supported by well-designed RCT evidence. Depression associations are from large observational studies — plausible mechanistically but not proven causally. The COVID-19 trial provides reassurance about safety at typical doses and suggests modest benefit for respiratory infections broadly. The primary evidence gap is a large RCT powered to detect effects on depression or long-term cardiovascular outcomes.","deepTruncated":false,"references":[{"id":"1","title":"Prevention of covid-19 and other acute respiratory infections with cod liver oil supplementation, a low dose vitamin D supplement: quadruple blinded, randomised placebo controlled trial","authors":"Brunvoll SH, Nygaard AB, Ellingjord-Dale M, Holland P, Istre MS, Kalleberg KT, Søraas CL, Holven KB, Ulven SM, Hjartåker A, Haider T, Lund-Johansen F, Dahl JA, Meyer HE, Søraas A","year":2022,"journal":"BMJ","pmid":"36215222","url":"https://pubmed.ncbi.nlm.nih.gov/36215222/"},{"id":"2","title":"Associations between cod liver oil use and symptoms of depression: the Hordaland Health Study","authors":"Raeder MB, Steen VM, Vollset SE, Bjelland I","year":2007,"journal":"Journal of Affective Disorders","pmid":"17184843","url":"https://pubmed.ncbi.nlm.nih.gov/17184843/"},{"id":"3","title":"Cod liver oil (n-3 fatty acids) as a non-steroidal anti-inflammatory drug sparing agent in rheumatoid arthritis","authors":"Galarraga B, Ho M, Youssef HM, Hill A, McMahon H, Hall C, Ogston S, Nuki G, Belch JJF","year":2008,"journal":"Rheumatology","pmid":"18362100","url":"https://pubmed.ncbi.nlm.nih.gov/18362100/"},{"id":"4","title":"Regular consumption of cod liver oil is associated with reduced basal and exercise-induced C-reactive protein levels; a prospective observational trial: A NEEDED (The North Sea Race Endurance Exercise Study) 2014 sub-study","authors":"Hansen MW, Ørn S, Erevik CB, Bjørkavoll-Bergseth MF, Skadberg Ø, Melberg TH, et al.","year":2021,"journal":"Journal of the International Society of Sports Nutrition","pmid":"34183020","url":"https://pubmed.ncbi.nlm.nih.gov/34183020/"},{"id":"5","title":"Cod liver oil supplement consumption and health: cross-sectional results from the EPIC-Norfolk cohort study","authors":"Lentjes MA, Welch AA, Mulligan AA, Luben RN, Wareham NJ, Khaw KT","year":2014,"journal":"Nutrients","pmid":"25325252","url":"https://pubmed.ncbi.nlm.nih.gov/25325252/"}],"wordCount":1502,"source":{"path":"src/content/topics/cod-liver-oil/vitamins-and-omega-3.md"},"citeAs":"“What does cod liver oil actually do for your health?.” What's Healthy and Why. https://whatshealthyandwhy.com/cod-liver-oil/vitamins-and-omega-3","notice":"General information backed by peer-reviewed research, not medical advice."}