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Cod Liver Oil Side Effects & Safety

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

Safety Profile

Overall safety rating: Generally Safe

Potential Side Effects

  • Fishy aftertaste and burping — the most common complaint; reduced by enteric-coated capsules, taking with meals, or refrigerating liquid oil
  • GI discomfort — nausea, loose stools, or heartburn at higher doses
  • Vitamin A toxicity risk — unlike regular fish oil, cod liver oil contains preformed vitamin A (retinol); chronic intake above 10,000 IU/day can cause liver damage, headache, and bone thinning
  • Mild anticoagulant effect — omega-3s inhibit platelet aggregation; may increase bruising at high doses
  • Fishy body odor at higher doses reported by some users

Drug & Supplement Interactions

  • Anticoagulants (warfarin, heparin, aspirin) — omega-3s inhibit platelet aggregation; additive bleeding risk
  • Retinoid medications (isotretinoin, acitretin) — additive vitamin A toxicity; concurrent use may cause hypervitaminosis A
  • Vitamin D supplements — cod liver oil already provides vitamin D; combined intake may exceed safe upper limits
  • Antihypertensives — omega-3s may modestly lower blood pressure; additive hypotensive effect possible
  • Orlistat — fat-blocking drugs reduce absorption of fat-soluble vitamins A and D from cod liver oil

Maximum Dose

Do not exceed: 2 teaspoons (10ml) daily — higher doses risk vitamin A toxicity (hypervitaminosis A); if more omega-3s are needed, supplement with regular fish oil

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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
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  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