Vitamin A is a group of compounds that play an important role in vision, bone growth, reproduction, cell division, and cell differentiation (in which a cell becomes part of the brain, muscle, lungs, blood, or other specialized tissue.)1 2 3 4 5

Vitamin A helps regulate the immune system, which helps prevent or fight off infections by making white blood cells that destroy harmful bacteria and viruses.6 7 8 9 10 11 Vitamin A also may help lymphocytes (a type of white blood cell) fight infections more effectively.

Vitamin A promotes healthy surface linings of the eyes and the respiratory, urinary, and intestinal tracts.12 When those linings break down, it becomes easier for bacteria to enter the body and cause infection. Vitamin A also helps the skin and mucous membranes function as a barrier to bacteria and viruses.13 14 15

In general, there are two categories of vitamin A, depending on whether the food source is an animal or a plant.

Vitamin A found in foods that come from animals is called preformed vitamin A. It is absorbed in the form of retinol, one of the most usable (active) forms of vitamin A. Sources include liver, whole milk, and some fortified food products. Retinol can be made into retinal and retinoic acid (other active forms of vitamin A) in the body.16

Vitamin A that is found in colorful fruits and vegetables is called provitamin A carotenoid. They can be made into retinol in the body.

In the United States, approximately 26% of vitamin A consumed by men and 34% of vitamin A consumed by women is in the form of provitamin A carotenoids.17

Common provitamin A carotenoids found in foods that come from plants are beta-carotene, alpha-carotene, and beta-cryptoxanthin.18 Among these, beta-carotene is most efficiently made into retinol.19 20 21 22 Alpha-carotene and beta-cryptoxanthin are also converted to vitamin A, but only half as efficiently as beta-carotene.23

Of the 563 identified carotenoids, fewer than 10% can be made into vitamin A in the body.24 Lycopene, lutein, and zeaxanthin are carotenoids that do not have vitamin A activity but have other health promoting properties.25 The Institute of Medicine (IOM) encourages consumption of all carotenoid-rich fruits and vegetables for their health-promoting benefits.

Some provitamin A carotenoids have been shown to function as antioxidants in laboratory studies; however, this role has not been consistently demonstrated in humans.26 Antioxidants protect cells from free radicals, which are potentially damaging by-products of oxygen metabolism that may contribute to the development of some chronic diseases.27 28 29

Related Links:  What is vitamin A? | What foods provide vitamin A? | How much vitamin A do I need? | What happens if I do not get enough vitamin A? | Do I need extra vitamin A? | Can vitamin A be harmful? | What are some of the current issues and controversies about vitamin A?

Disclaimer
Reasonable care has been taken in preparing this document and the information provided herein is believed to be accurate. However, this information is not intended to constitute an “authoritative statement” under Food and Drug Administration rules and regulations.

About Source: ODS

The mission of the Office of Dietary Supplements (ODS) is to strengthen knowledge and understanding of dietary supplements by evaluating scientific information, stimulating and supporting research, disseminating research results, and educating the public to foster an
enhanced quality of life and health for the U.S. population.

General Safety Advisory

Health professionals and consumers need credible information to make thoughtful decisions about eating a healthful diet and using vitamin and mineral supplements. These Fact Sheets provide responsible information about the role of vitamins and minerals in health and disease. Each Fact Sheet in this series received extensive review by recognized experts from the academic and research communities.

The information is not intended to be a substitute for professional medical advice. It is important to seek the advice of a physician about any medical condition or symptom. It is also important to seek the advice of a physician, registered dietitian, pharmacist, or other qualified health professional about the appropriateness of taking dietary supplements and their potential interactions with medications.

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Footnotes

  1. Institute of Medicine. Food and Nutrition Board. Dietary Reference Intakes for Vitamin A, Vitamin K, Arsenic, Boron, Chromium, Copper, Iodine, Iron, Manganese, Molybdenum, Nickel, Silicon, Vanadium, and Zinc. National Academy Press, Washington, DC, 2001. [↩]
  2. Gerster H. Vitamin A-functions, dietary requirements and safety in humans. Int J Vitam Nutr Res 1997;67:71-90. PubMed abstract [↩]
  3. Futoryan T, Gilchrest BE. Retinoids and the skin. Nutr Rev 1994;52:299-310. PubMed abstract [↩]
  4. Hinds TS, West WL, Knight EM. Carotenoids and retinoids: A review of research, clinical, and public health applications. J Clin Pharmacol 1997;37:551-8. PubMed abstract [↩]
  5. Ross AC, Gardner EM. The function of vitamin A in cellular growth and differentiation, and its roles during pregnancy and lactation. Adv Exp Med Biol 1994;352:187-200. PubMed abstract [↩]
  6. Institute of Medicine. Food and Nutrition Board. Dietary Reference Intakes for Vitamin A, Vitamin K, Arsenic, Boron, Chromium, Copper, Iodine, Iron, Manganese, Molybdenum, Nickel, Silicon, Vanadium, and Zinc. National Academy Press, Washington, DC, 2001. [↩]
  7. Ross AC. Vitamin A and retinoids. In: Modern Nutrition in Health and Disease. 9th Edition (edited by Shils ME, Olson J, Shike M, Ross AC). Lippincott Williams and Wilkins, New York, 1999, pp. 305-27. [↩]
  8. Ross AC, Stephensen CB. Vitamin A and retinoids in antiviral responses. FASEB J 1996;10:979-85. PubMed abstract [↩]
  9. Semba RD. The role of vitamin A and related retinoids in immune function. Nutr Rev 1998;56:S38-48. PubMed abstract [↩]
  10. Ross DA. Vitamin A and public health: Challenges for the next decade. Proc Nutr Soc 1998;57:159-65. PubMed abstract [↩]
  11. Harbige LS. Nutrition and immunity with emphasis on infection and autoimmune disease. Nutr Health 1996;10:285-312. PubMed abstract [↩]
  12. Semba RD. The role of vitamin A and related retinoids in immune function. Nutr Rev 1998;56:S38-48. PubMed abstract [↩]
  13. Ross DA. Vitamin A and public health: Challenges for the next decade. Proc Nutr Soc 1998;57:159-65. PubMed abstract [↩]
  14. Harbige LS. Nutrition and immunity with emphasis on infection and autoimmune disease. Nutr Health 1996;10:285-312. [PubMed abstract [↩]
  15. de Pee S, West CE. Dietary carotenoids and their role in combating vitamin A deficiency: A review of the literature. Eur J Clin Nutr 1996;50 Suppl 3:S38-53. PubMed abstract [↩]
  16. Institute of Medicine. Food and Nutrition Board. Dietary Reference Intakes for Vitamin A, Vitamin K, Arsenic, Boron, Chromium, Copper, Iodine, Iron, Manganese, Molybdenum, Nickel, Silicon, Vanadium, and Zinc. National Academy Press, Washington, DC, 2001. [↩]
  17. Institute of Medicine. Food and Nutrition Board. Dietary Reference Intakes for Vitamin A, Vitamin K, Arsenic, Boron, Chromium, Copper, Iodine, Iron, Manganese, Molybdenum, Nickel, Silicon, Vanadium, and Zinc. National Academy Press, Washington, DC, 2001. [↩]
  18. de Pee S, West CE. Dietary carotenoids and their role in combating vitamin A deficiency: A review of the literature. Eur J Clin Nutr 1996;50 Suppl 3:S38-53. PubMed abstract [↩]
  19. Institute of Medicine. Food and Nutrition Board. Dietary Reference Intakes for Vitamin A, Vitamin K, Arsenic, Boron, Chromium, Copper, Iodine, Iron, Manganese, Molybdenum, Nickel, Silicon, Vanadium, and Zinc. National Academy Press, Washington, DC, 2001. [↩]
  20. Olson JA, Kobayashi S. Antioxidants in health and disease: Overview. Proc Soc Exp Biol Med 1992;200:245-7. PubMed abstract [↩]
  21. Olson JA. Benefits and liabilities of vitamin A and carotenoids. J Nutr 1996;126:1208S-12S. [PubMed abstract [↩]
  22. Pavia SA, Russell RM. Beta-carotene and other carotenoids as antioxidants. J Am Coll Nutr 1999;18:426-33. [PubMed abstract [↩]
  23. Institute of Medicine. Food and Nutrition Board. Dietary Reference Intakes for Vitamin A, Vitamin K, Arsenic, Boron, Chromium, Copper, Iodine, Iron, Manganese, Molybdenum, Nickel, Silicon, Vanadium, and Zinc. National Academy Press, Washington, DC, 2001. [↩]
  24. Bendich A, Olson JA. Biological actions of carotenoids. FASEB J 1989:3;1927-32 PubMed abstract [↩]
  25. Institute of Medicine. Food and Nutrition Board. Dietary Reference Intakes for Vitamin A, Vitamin K, Arsenic, Boron, Chromium, Copper, Iodine, Iron, Manganese, Molybdenum, Nickel, Silicon, Vanadium, and Zinc. National Academy Press, Washington, DC, 2001. [↩]
  26. Institute of Medicine. Food and Nutrition Board. Dietary Reference Intakes for Vitamin A, Vitamin K, Arsenic, Boron, Chromium, Copper, Iodine, Iron, Manganese, Molybdenum, Nickel, Silicon, Vanadium, and Zinc. National Academy Press, Washington, DC, 2001. [↩]
  27. Futoryan T, Gilchrest BE. Retinoids and the skin. Nutr Rev 1994;52:299-310. PubMed abstract [↩]
  28. Olson JA. Benefits and liabilities of vitamin A and carotenoids. J Nutr 1996;126:1208S-12S. PubMed abstract [↩]
  29. Pavia SA, Russell RM. Beta-carotene and other carotenoids as antioxidants. J Am Coll Nutr 1999;18:426-33. PubMed abstract [↩]

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