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Benefits of Cod Liver Oil

Evidence:Moderate
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This content is for informational purposes only and does not constitute medical advice. Statements about dietary supplements have not been evaluated by the FDA and are not intended to diagnose, treat, cure, or prevent any disease. Individual results may vary — consult your healthcare provider before starting any supplement. Full disclaimer

Evidence-Based Benefits

  • Bone health — cod liver oil's vitamin D3 content promotes calcium absorption and bone mineralization, while omega-3s reduce bone resorption. The VITAL study (Manson et al., 2019) and decades of research confirm vitamin D supplementation reduces fracture risk in deficient populations
  • Cardiovascular protection — EPA and DHA from cod liver oil reduce triglycerides, lower blood pressure, and decrease inflammatory markers. A meta-analysis by Aung et al. (2018) of 77,000+ participants found omega-3 supplementation reduced coronary heart disease events
  • Immune function — vitamins A and D are both critical for immune regulation. Vitamin D activates antimicrobial peptides (cathelicidin) while vitamin A maintains mucosal barrier integrity. Martineau et al. (2017) meta-analysis showed vitamin D supplementation reduced respiratory tract infections
  • Anti-inflammatory effects — EPA and DHA are precursors to specialized pro-resolving mediators (resolvins, protectins) that actively resolve inflammation. Goldberg & Katz (2007) meta-analysis found fish oil supplementation significantly reduced joint pain and morning stiffness in rheumatoid arthritis
  • Eye health — DHA is a major structural component of retinal photoreceptors, and vitamin A (retinol) is essential for rhodopsin synthesis. Combined, they support both structural and functional aspects of vision

What the Research Says

Cod Liver Oil is a well-researched supplement that combines omega-3 fatty acids and vitamins A and D, offering various health benefits supported by both historical and contemporary studies. For bone health, vitamin D's role in calcium absorption and fracture prevention is highlighted by the VITAL study (Manson et al., 2019), which remains the largest randomized trial on this topic.

In cardiovascular outcomes, a meta-analysis of 10 trials involving 77,917 participants conducted by Aung et al. (2018) found that omega-3 supplementation reduced coronary heart disease events by 8%. However, it is important to note that the same study did not find a significant association between omega-3 fatty acid supplementation and major vascular events.

For respiratory health, Martineau et al. (2017) meta-analyzed 25 RCTs and reported that vitamin D supplementation decreased the risk of acute respiratory tract infections, particularly in individuals with vitamin D deficiency. This finding was supported by a 2022 randomized controlled trial involving 34,601 adults, which found that daily cod liver oil supplementation did not reduce the risk of SARS-CoV-2 infection or other acute respiratory infections compared to placebo (Brunvoll et al., 2022).

Cod liver oil also demonstrates benefits for joint inflammation. Goldberg & Katz (2007) confirmed that fish oil reduces pain and stiffness in rheumatoid arthritis through a meta-analysis of 17 randomized controlled trials. Additionally, Rajakumar (2003) highlighted cod liver oil's historical role in eliminating rickets as a public health issue.

A key distinction of cod liver oil compared to regular fish oil is its vitamin A content, which offers synergistic immune and bone benefits but also poses a risk of toxicity due to its upper intake limit. The evidence for cod liver oil is classified as Moderate because while omega-3 and vitamin D evidence are individually strong, there are fewer cod liver oil-specific RCTs compared to purified fish oil or vitamin D alone.

Related Conditions

Bone HealthImmune FunctionHeart HealthInflammationEye Health
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References

  1. RCTManson JE, Cook NR, Lee IM, Christen W, Bassuk SS, Mora S, Gibson H, Gordon D, Copeland T, D'Agostino D, Friedenberg G, Ridge C, Bubes V, Giovannucci EL, Willett WC, Buring JE (2019). Vitamin D supplements and prevention of cancer and cardiovascular disease. New England Journal of Medicine. DOI PubMed
  2. Meta-analysisAung T, Halsey J, Kromhout D, Gerstein HC, Marchioli R, Tavazzi L, Geleijnse JM, Rauch B, Ness A, Galan P, Chew EY, Bosch J, Collins R, Lewington S, Armitage J, Clarke R (2018). Associations of omega-3 fatty acid supplement use with cardiovascular disease risks: meta-analysis of 10 trials involving 77917 individuals. JAMA Cardiology. DOI PubMed
  3. Meta-analysisMartineau AR, Jolliffe DA, Hooper RL, Greenberg L, Aloia JF, Bergman P, Dubnov-Raz G, Esposito S, Ganmaa D, Ginde AA, Goodall EC, Grant CC, Griffiths CJ, Janssens W, Laaksi I, Manaseki-Holland S, Mauger D, Murdoch DR, Neale R, Rees JR, Simpson S, Stelmach I, Kumar GT, Urashima M, Camargo CA (2017). Vitamin D supplementation to prevent acute respiratory tract infections: systematic review and meta-analysis of individual participant data. BMJ. DOI PubMed
  4. Meta-analysisGoldberg RJ, Katz J (2007). A meta-analysis of the analgesic effects of omega-3 polyunsaturated fatty acid supplementation for inflammatory joint pain. Pain. DOI PubMed
  5. Rajakumar K (2003). Vitamin D, cod-liver oil, sunlight, and rickets: a historical perspective. Pediatrics. DOI PubMed
  6. RCTBrunvoll SH, Nygaard AB, Ellingjord-Dale M, Holland P, et al. (2022). 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.. BMJ (Clinical research ed.). DOI PubMed
  7. Purzand B, Rokhgireh S, Shabani Zanjani M, Eshraghi N, et al. (2020). The comparison of the effect of soybean and fish oil on supplementation on menopausal symptoms in postmenopausal women: A randomized, double-blind, placebo-controlled trial.. Complementary therapies in clinical practice. DOI PubMed
Show 4 more references
  1. Conus N, Burgher-Kennedy N, van den Berg F, Kaur Datta G (2019). A randomized trial comparing omega-3 fatty acid plasma levels after ingestion of emulsified and non-emulsified cod liver oil formulations.. Current medical research and opinion. DOI PubMed
  2. Miragliotta G, Miragliotta L (2014). Vitamin D and infectious diseases.. Endocrine, metabolic & immune disorders drug targets. DOI PubMed
  3. Feher J, Pinter E, Kovács I, Helyes Z, et al. (2014). Irritable eye syndrome: neuroimmune mechanisms and benefits of selected nutrients.. The ocular surface. DOI PubMed
  4. Dyerberg J, Madsen P, Møller JM, Aardestrup I, et al. (2010). Bioavailability of marine n-3 fatty acid formulations.. Prostaglandins, leukotrienes, and essential fatty acids. DOI PubMed