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Cod Liver Oil

Vitamin a is also found in cod liver oil. Based on UK recommendations1 two typical doses of cod liver oil2 will provide double your RDA of vitamin a. This may be an issue and if you supplement with cod liver oil and a multivitamin you should ensure you take a multivitamin that does not include vitamin a.

If you eat oily fish regularly, there is no need to supplement with cod liver oil or vitamin a.

Pregnant women and those trying for a baby should not take any supplements that contain vitamin a, including cod liver oil.

The UK's National Clinical and Health Care Excellence (NICE) organisation states there is no evidence that omega-3 fatty acid compounds (i.e supplements) help to prevent cardiovascular disease (CVD).3 This suggests omega 3 must be obtained from the flesh of oily fish and other seafoods, rather than the oil extracted from fish livers.

Note

Delay taking any supplements for 30-60 minutes after consuming coffee as it contains compounds (polyphenols) that limit the absorption of many micronutrients.

Forms/Types

Quality

As with all supplements - buyer beware. It's quite common for supplements to be contaminated with a variety of impurities, often in the form of heavy metals, and/or contain far more or less of the ingredients stated on the label. There's no simple rule of thumb to avoid this, such as avoiding cheap or imported products; expensive or well-known brands produced in-country may be just as bad. Ideally you should take some time to find products (if you can) that;

  • have been laboratory tested on behalf of the manufacturer by a reputable body or company that operates in your country or region (here's an example of a Peak Supps creatine supplement available on Amazon in the UK which has been tested by Eurofins: Creatine Monohydrate Powder 1Kg | Pure Micronised | Packaging May Vary - see pictures 3 & 4)
  • in the UK & EU, are manufactured in facilities that meet the minimum standards of good manufacturing practice (GMP) in their production processes (for medicines).45 Facilities are inspected for compliance and manufacturers' product(s) must:
    • be of consistent high quality
    • be appropriate to their intended use
    • meet the requirements of the marketing authorisation (MA) or product specification

Be wary of any manufacturers or brands making claims around these valid but irrelevant standards;

  • HACCP: this standard relates to food safety which indicates that the seller is claiming their supplement is a food; whilst meeting this standard is worthwhile, GMP (detailed above) would be a more appropriate standard
  • ISO22000: same as HACPP
  • ISO9001: this standard is focussed on quality control management systems in the context of managing a business or organisation, not directly on the the quality of the products that business produces (although it may have a beneficial impact)

Dosage - How Much?

Deficiency - Too Little

Toxicity - Too Much

Side Effects

When to Avoid Use - Interactions/Contraindications

  • don't have too much if on blood thinners as this could impair blood clotting.

Random Facts

Metadata

Created:

Last Updated: 2026-03-05

References

  1. Vitamin A - retrieved 2025-02-13 ↩

  2. Cod Liver Oil 1000mg, 360 Capsules of High Strength Fish Oil, Rich in Omega 3. Supports Heart Health, Brain Health, Eye Health and Normal Blood Pressure - retrieved 2025-09-30, the brand is Zipvit ↩

  3. Cardiovascular disease: risk assessment and reduction, including lipid modification. NICE guideline: Reference number:NG238, Published: 14 December 2023 ↩

  4. Medicines: good manufacturing practice and good distribution practice ↩

  5. Good manufacturing practice ↩