SUPPLEMENT SCIENCEInsights
Search

Search Insights

Try choline, nano-curcumin or probiotics.

    Ingredient guide · Ingredient reference

    Cod liver oil: check vitamin A as well as vitamin D

    Cod liver oil can supply more than one fat-soluble vitamin. Choosing it for vitamin D without checking vitamin A can overlook an important part of the exposure.

    Read the evidence ↓

    Supplement Science Insights Editorial Team

    Published September 23, 2026

    The product is not simply vitamin D in oil

    Cod liver oil also supplies long-chain omega-3 fatty acids, including EPA and DHA. Their amounts are separate from both the total oil weight and the vitamin A/D declarations. A label stating a gram of oil does not mean a gram of EPA plus DHA. Compare those fatty acids and both vitamins per the same serving; none of the four quantities can be reliably inferred from the product name alone. [1][2][4]

    ODS lists cod liver oil among vitamin D sources, while NHS guidance highlights fish liver oil as a source of vitamin A. The quantities in a particular product depend on its formulation and serving size. A general food-table entry is not a verified assay of every bottle. [1][2][4]

    Check the amount of each vitamin per serving, the serving volume and any other supplements used. Fish oil and fish liver oil should not be treated as identical nutrient profiles merely because both are oils from fish. [1][2][4]

    One nutrient goal can change another exposure

    Preformed vitamin A can accumulate, and its adult upper limit includes food and supplements. A decision to increase cod liver oil for one vitamin may therefore increase another nutrient unintentionally. Pregnancy requires particular attention to vitamin A form and amount. [3][2]

    There is no universal vitamin A concentration to infer solely from the words cod liver oil. Use the actual declaration and clinical context rather than a fixed teaspoon rule. [3][2]

    Assess both columns before scaling the serving

    Imagine someone doubles a cod liver oil serving to obtain more vitamin D. If the formulation also contains vitamin A, that amount doubles too. The calculation must include both nutrients and the rest of the daily intake.

    Hypothetical example — keep the amount, form and context together
    DetailMeaning
    Serving volumeDefines the declared amounts
    Vitamin D goalDoes not erase vitamin A
    Other supplementsCount overlapping sources
    Cod liver oil: check vitamin A as well as vitamin D — original article outline diagram
    Original editorial diagram of this article’s sections; no product photograph or clinical finding is depicted.

    Sources for this article

    1. NIH ODS: Vitamin D
      Source consulted: 2026-09-17. This is a reference resource, not a claim that we conducted the studies or tested a product.
    2. NHS: Vitamin A
      Source consulted: 2026-09-17. This is a reference resource, not a claim that we conducted the studies or tested a product.
    3. NIH ODS: Vitamin A and Carotenoids
      Source consulted: 2026-09-17. This is a reference resource, not a claim that we conducted the studies or tested a product.
    4. NIH ODS: Omega-3 Fatty Acids
      Source consulted: 2026-09-20. This is a reference resource, not a claim that we conducted the studies or tested a product.