Vitamin A

Vitamin A is a term for a large number of related compounds (e.g., retinol, retinal, retinoic acid), which are known as ’retinoids’.

The vitamin A form found in foods that come from animals is retinol (also called ’preformed vitamin A’), a yellow, fat-soluble vitamin, and the precursor of the most active form of vitamin A (retinoic acid) used in the body.

The vitamin A form found in fruits and vegetables is called ’provitamin A carotenoid’ (e.g. beta-carotene), which can be converted into retinol in the body.

Health functions

Vitamin A (retinol) has several functions in the body. The most well known is its role in vision. Retinol is transported to the retina, located at the back of the eye, where it is oxidized to retinal.

Disease risk reduction

Because of the possible roles of vitamin A in reversing tumor development and boosting immune function, it has been proposed that retinol might help reduce cancer risk.

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Things to know about Vitamin A

  • Other applications

    Retinitis pigmentosa, the progressive loss of photoreceptor cells in the eye's retina (20), results in a loss of peripheral and central vision over time.

  • Intake recommendations

    The intake recommendations for vitamin A are based on the amount needed to ensure adequate stores (four months) of retinol in the body to support normal reproductive function, immune function, gene expression, and vision.

  • Supply situation

    Surveys undertaken in several countries suggest that intake patterns vary considerably across Europe and the U.S. The number of people at risk of vitamin A deficiency depends on the intake of total vitamin A, which is defined as preformed (retinol) plus provitamin A (e.g. beta-carotene).

  • Deficiency

    Vitamin A deficiency usually results from inadequate intake of foods high in vitamin A (see Sources) or beta-carotene; a precursor of vitamin A.

  • Sources

    While free retinol is not generally found in foods, retinyl palmitate, a precursor and storage form of retinol, is found in animal-derived foods such as liver, milk, milk products, egg yolks, cheese, and fish.

  • Safety

    Acute vitamin A toxicity (hypervitaminosis), caused by preformed vitamin A (retinol), which is rapidly absorbed and slowly cleared from the body, is relatively rare.

  • References

    Consult the full list of scientific references.