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Moderate evidenceGeneral health

Cod Liver Oil

Cod liver oil is a cheap, traditional source of EPA, DHA, vitamin D and vitamin A, and it works as a food-based omega-3 and vitamin D supplement. Its specific claims about preventing infections did not hold up in a large randomized trial, and the vitamin A load caps how much you can safely take.

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What the science says

  • Provides EPA, DHA and vitamin D in usable amounts Strong evidence

    A standard 5 mL teaspoon supplies roughly 800-1,000 mg combined EPA+DHA plus about 10 mcg (400 IU) vitamin D, so it delivers omega-3 and vitamin D at doses used in clinical trials. For triglyceride lowering and correcting vitamin D deficiency, the evidence supporting those individual nutrients carries over directly.

  • Does not prevent COVID-19 or other respiratory infections Strong evidence

    A quadruple-blinded randomized trial in 34,741 Norwegian adults gave 5 mL/day cod liver oil or placebo for up to six months and found no reduction in SARS-CoV-2 infection, COVID-19 severity, or other acute respiratory infections. Baseline vitamin D status in the cohort was already adequate, which is consistent with meta-analysis data showing vitamin D reduces respiratory infections mainly in people who are deficient.

  • Corrects vitamin D deficiency Moderate evidence

    Individual participant data meta-analysis of 25 vitamin D trials (11,321 participants) found a protective effect against acute respiratory infection driven almost entirely by people with baseline 25(OH)D below 25 nmol/L, where the odds ratio was about 0.30. Cod liver oil is a reasonable delivery vehicle for that correction, but it is a low-dose vitamin D source and pure vitamin D3 is more efficient if that is the goal.

Dosage & safety

Studied dose5 mL (one teaspoon) daily is the traditional dose, providing roughly 800-1,000 mg EPA+DHA, ~10 mcg vitamin D and ~250-800 mcg retinol depending on brand. Do not scale up freely to reach higher omega-3 doses — use plain fish oil instead.
SafetyThe limiting factor is preformed vitamin A (retinol). Cumulative high intake is linked to reduced bone mineral density and liver toxicity, and it is teratogenic — pregnant women should not take unrestricted cod liver oil, and doses should keep total retinol below about 3,000 mcg/day. Avoid stacking with a multivitamin containing retinol. Mild antiplatelet effect at higher omega-3 intakes; disclose before surgery and use caution with anticoagulants. Fishy burps and GI upset are common.

How to take it

TimingTiming does not matter.
With food?With a meal containing fat — it carries the fat-soluble vitamins A and D as well as the omega-3s.
Worth knowingDo not scale the dose up to chase a higher omega-3 intake; the retinol scales with it, and plain fish oil is the right tool for that job.

Interactions

With medications

  • isotretinoin, acitretin and other retinoid drugs

    Cod liver oil supplies preformed retinol, which adds to retinoid therapy and increases the risk of vitamin A toxicity. do not combine

  • warfarin, DOACs and antiplatelet drugs

    Mild antiplatelet effect from the omega-3 content at higher intakes. tell your prescriber and disclose it before surgery

With other supplements

  • multivitamins and any product containing retinol

    Preformed vitamin A adds up, and cumulative high intake is linked to reduced bone density, liver toxicity and birth defects. add up total retinol and keep it under about 3,000 mcg/day

Well-established interactions only — this is not a complete list. Always tell your doctor and pharmacist what you take.

Frequently asked questions

What are the benefits of cod liver oil?

Cod liver oil is a well-supported source of omega-3 and vitamin D: a 5 mL teaspoon supplies roughly 800-1,000 mg EPA+DHA and about 10 mcg (400 IU) vitamin D. The benefits of those nutrients, such as triglyceride lowering and correcting vitamin D deficiency, carry over directly.

Does cod liver oil prevent colds, flu or COVID-19?

No: a randomised trial in 34,741 Norwegian adults found 5 mL/day of cod liver oil for up to six months did not reduce COVID-19 or other acute respiratory infections. Vitamin D appears to help mainly in people who are deficient.

How much cod liver oil is safe per day?

The traditional cod liver oil dose is 5 mL (one teaspoon) daily. Do not scale it up to get more omega-3, because the vitamin A (retinol) rises with it; keep total retinol from all sources below about 3,000 mcg/day and use plain fish oil for higher omega-3 doses.

Can I take cod liver oil during pregnancy or with a multivitamin?

Cod liver oil's preformed vitamin A is teratogenic, so pregnant women should not take it unrestricted. Avoid stacking cod liver oil with a multivitamin that contains retinol, and do not combine it with retinoid drugs such as isotretinoin.

Scientific references

Where to buy

NOW Foods, Cod Liver Oil, 1,000 mg, 180 Softgels

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