Image for Vitamin A (retinol)
Vitamin A (retinol)

Synonyms/Common Names/Related Substances:

  • 3,7-Dimethyl-9-(2,6,6,trimethyl-1-cyclohexen-1-yl)-2,4,6,8-natetraen-1-ol, 3-dehydroretinol, Accutane®, acitretin, adapalene, alitretinoin, all-trans retinoic acid, Altinac®, Amnesteem®, antixerophthalmic vitamin, Aquasol A®, Avita®, axerophtholum, beta-carotene, beta-carotene oleovitamin A, bexarotene, carotenoids, Differin®, etretinate, isotretinoin, Palmitate-A®, Renova®, Retin-A®, Retin-A Micro®, retinaldehyde (RAL), retinyl acetate, retinyl N-formyl aspartamate, retinyl palmitate, retinoic acid, retinol, Solatene®, Soriatane®, SourceCF®, Targretin®, tazarotene, Tazorac®, Tegison®, topical retinoids, tretinoin, Vesabiod®, Vesanoid®, Vitamax®, vitamin A USP, vitamin A1, vitamina A, vitaminum A.
  • Note: The Evidence Table and Evidence Discussion for this monograph are limited to meta-analyses and systematic reviews of intervention studies.

Clinical Bottom Line/Effectiveness

Brief Background:

  • Vitamin A is a fat-soluble vitamin that is derived from two sources: preformed retinoids and provitamin carotenoids. Retinoids, such as retinal and retinoic acid, are found in animal sources such as liver, kidney, eggs, and dairy produce. Carotenoids such as beta-carotene (which has the highest vitamin A activity) are found in plants such as dark or yellow vegetables, carrots, and tree nuts (1).
  • Natural retinoids are present in all living organisms, either as preformed vitamin A or as carotenoids, and they are required for a vast number of biological processes, such as vision and cellular growth. Vitamin A is considered a type 1 nutrient, required for specific biological functions, compared to type 2 nutrients that are required for general metabolism (2). A major biological function of vitamin A (as the metabolite retinal) is in the visual cycle. Research also suggests that vitamin A may reduce the mortality rate from measles, prevent some types of cancer, aid in growth and development, and improve immune function.
  • The recommended dietary allowance (RDA) levels for vitamin A oral intake have been established by the U.S. Institute for Medicine of the National Academy of Sciences to prevent deficiencies in vitamin A.
  • The health benefits of vitamin A supplementation may be confounded by the fact that vitamin users have better health patterns overall than nonusers. For example, in elderly Japanese men residing in Hawaii, vitamin A is the fourth-most popular form of supplementation (after multivitamins, vitamin C, and vitamin E), and vitamin users were more physically active, less obese, and less likely to use alcohol, tobacco, or caffeine (3).
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Dosing/Toxicology

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Precautions/Contraindications

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Interactions

Most herbs and supplements have not been thoroughly tested for interactions with other herbs, supplements, drugs, or foods. The interactions listed below are based on reports in scientific publications, laboratory experiments, or traditional use. You should always read product labels. If you have a medical condition, or are taking other drugs, herbs, or supplements, you should speak with a qualified healthcare provider before starting a new therapy.

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Mechanism of Action

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History

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Evidence Table

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Evidence Discussion

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Products Studied

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Author Information

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References

Natural Standard developed the above evidence-based information based on a thorough systematic review of the available scientific articles. For comprehensive information about alternative and complementary therapies on the professional level, go to www.naturalstandard.com. Selected references are listed below.

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The information in this monograph is intended for informational purposes only, and is meant to help users better understand health concerns. Information is based on review of scientific research data, historical practice patterns, and clinical experience. This information should not be interpreted as specific medical advice. Users should consult with a qualified healthcare provider for specific questions regarding therapies, diagnosis and/or health conditions, prior to making therapeutic decisions.