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Cod Liver Oil
A traditional fish-liver oil delivering EPA/DHA omega-3s plus naturally occurring vitamins A and D. The evidence is mixed: a small RCT showed NSAID-sparing benefit in rheumatoid arthritis, but a very large RCT found it did NOT prevent COVID-19 or other respiratory infections. Largely overlaps plain omega-3 fish oil.
What the evidence says
Most Cod Liver Oil studies are mechanism or observational rather than RCTs that measure a clinical effect — keep findings provisional.
Most evidence is from medium-quality randomised trials published 2000–2022 with a typical study size of 1,156 participants.
Based on 4 studies · 2 RCTs · 35,948 total participants
Confidence
LowCod Liver Oil has an evidence score of 4/10 — emerging evidence based on 4 indexed studies. A traditional fish-liver oil delivering EPA/DHA omega-3s plus naturally occurring vitamins A and D. The evidence is mixed: a small RCT showed NSAID-sparing benefit in rheumatoid arthritis, but a very large RCT found it did NOT prevent COVID-19 or other respiratory infections. Largely overlaps plain omega-3 fish oil. Representative study: PMID 36215222.
The commonly studied dose of Cod Liver Oil is 5 mL/day (about 1 teaspoon), providing roughly 1-2g omega-3 plus modest vitamins A and D. Individual needs vary — start at the lower end of the range and adjust based on how you respond.
Explore: Best supplements for Vitality & Longevity
Last reviewed June 2026 · evidence from 4 studies · how we score
This information is for educational purposes only. It is not a substitute for professional medical advice. Always consult a qualified healthcare provider before starting, stopping, or changing any supplement or medication.
Cod liver oil is pressed from the livers of cod (Gadus species) and has been used for over a century, originally to prevent rickets. Unlike standard fish oil (which comes from body tissue), cod liver oil naturally contains fat-soluble vitamins A and D alongside the omega-3 fatty acids EPA and DHA. Its rationale rests on combining anti-inflammatory omega-3s with vitamin D's immune and bone roles. The honest evidence picture is mixed. The single best-supported finding is from a small double-blind RCT in rheumatoid arthritis, where cod liver oil let more patients cut their NSAID dose by over 30% — a real but modest NSAID-sparing effect. A pediatric study linked daily cod liver oil (with a multivitamin) to fewer upper-respiratory clinic visits, and an older Norwegian case-control study associated maternal cod liver oil use with lower offspring type-1 diabetes risk. However, the largest and most rigorous trial — a quadruple-blinded RCT of over 34,000 Norwegian adults — found cod liver oil did NOT prevent SARS-CoV-2 infection, serious COVID-19, or other acute respiratory infections. Because its omega-3 content overlaps plain fish oil and its vitamin A content imposes an upper limit, cod liver oil is best seen as a traditional combination product with modest, condition-specific evidence rather than a standout supplement.
Marine omega-3s reduce production of pro-inflammatory eicosanoids and support cardiovascular and membrane function.
Naturally present vitamin D supports immune modulation and bone mineralization, historically used to prevent rickets.
Preformed vitamin A supports vision, epithelial integrity, and immune function — but also imposes an upper intake limit.
How Cod Liver Oil works — from molecular targets to health outcomes. Click an edge to see supporting research.This visualization is in beta — pathways are being refined and expanded.
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5 mL/day (about 1 teaspoon), providing roughly 1-2g omega-3 plus modest vitamins A and D
Take with food
| Form | Type |
|---|---|
| 💧Liquid cod liver oil | Recommended |
| 💊Cod liver oil capsules | Alternative |
For omega-3 dosing alone, a standardized fish oil is more predictable; cod liver oil is chosen when the added vitamins A and D are also wanted.
Minimum: 8 weeks
Optimal: 24 weeks
Cycling: Not required
Note: Take with a fat-containing meal. Watch cumulative vitamin A intake if combining with other vitamin-A-containing supplements.
Dose-response data unavailable. The current published research for Cod Liver Oil does not provide sufficient dose-specific outcome data to generate reliable dose-response curves.
Refer to the Dosage & Timing section above for recommended dose ranges based on available evidence.
Helped more rheumatoid arthritis patients reduce NSAID dose by >30% versus placebo.
A 34,000-person RCT found no reduction in COVID-19 or other acute respiratory infections.
Provides modest doses of vitamins A and D alongside omega-3s.
Fishy burps and mild GI upset are common, as with other fish oils.
Caution — high preformed vitamin A is teratogenic. Standard low-dose cod liver oil is often used, but avoid high doses and account for vitamin A from all sources.
Use with caution and inform your clinician due to omega-3 effects on platelets.
Track total preformed vitamin A intake to avoid toxicity.
Omega-3 fatty acids can modestly affect platelet function; theoretical additive bleeding risk with warfarin, DOACs, or antiplatelet drugs.
Cumulative preformed vitamin A can reach toxic levels; avoid stacking with high-dose vitamin A or retinoids.
Cod liver oil already contains vitamin D; account for it when dosing additional vitamin D.
Tip: Take with meals or refrigerate
Tip: Take with food; reduce dose
Tip: Stay within recommended dose; avoid stacking vitamin A sources
Cod liver oil is an omega-3 source with added vitamins A and D; for higher EPA/DHA without vitamin A, a standard fish oil is cleaner. Generally use one or the other rather than stacking.
Together they cover omega-3 needs, but watch total dose and vitamin A — usually redundant.
Cod liver oil supplies some vitamin D; additional D3 can top up status in deficient individuals, but account for the amount already in the oil.
Complementary vitamin D support — adjust D3 dose for what cod liver oil already provides.
The best time to take Cod Liver Oil is with meals. Take it with food. Taking with a fat-containing meal improves absorption of the omega-3s and fat-soluble vitamins and reduces fishy reflux.
Cod Liver Oil is generally safe at recommended doses, with a few precautions worth noting. The most commonly reported side effects are fishy aftertaste / burps, mild GI upset / loose stools, vitamin A excess (at high doses). Use caution if any of these apply to you: Hypervitaminosis A; Concurrent high-dose vitamin A supplements.
Thymoquinone-rich oil studied for immune modulation, blood sugar control, and anti-inflammatory effects across numerous trials.