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, mostly as retinylesters (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, beta-cryptoxanthin), which can be converted into retinol in the body.

Authored by Dr Peter Engel in 2010, reviewed by Dr. Adrian Wyss on 31.08.2017.

Health functions

Vitamin A (retinol) plays an essential role in healthy vision, normal functioning of the immune system, embryonic development, and red blood cells.

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 recommended dietary allowance (RDA) of Vitamin A is dependent on age, gender, and other factors.

  • 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

    The earliest symptoms of vitamin A (beta-carotene) deficiency is impaired dark adaptation or night blindness.

  • Sources

    Foods high in retinyl palmitate, a precursor and storage form of vitamin A retinol, include milk, 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.