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You are here : 3-RX.com > Medical Encyclopedia > Diet and Nutrition > Vitamin A
      Category : Health Centers > Food, Nutrition, and Metabolism

Vitamin A

Alternate Names : Retinol, Retinal, Retinoic Acid, Carotenoids Including Beta-Carotene

Overview & Description | Functions and Sources

Vitamin A is a fat-soluble vitamin which means it can be dissolved in fat. Vitamin A is carried through the body by fat. The body can store this type of vitamin in fat tissue. Getting too much can be harmful.


Vitamin A is usually measured in retinol equivalents, also called RE. The Recommended Dietary Allowance, called RDA, for vitamin A for adult men, from age 11 on, is 1,000 RE per day. Women, from age 11 on, should get 800 RE per day. There is no increase of vitamin A requirements during pregnancy but lactating women need about 500 RE or more per day.

Vitamin A can be stored in the fat tissues of the body. This can pose a problem for people taking extra doses of vitamin A. High doses can be toxic and cause symptoms such as the following:

  • headaches
  • dry and scaly skin
  • liver damage
  • bone and joint pain
  • vomiting or lack of appetite
  • abnormal bone growth
  • nerve damage
  • birth defects
  • In most cases, only levels 10 times the RDA (far more than a person could get through diet alone) have been linked with these symptoms. Vitamin A cannot reach toxic levels unless a person is taking extra doses. Carotenoids are not converted to vitamin A fast enough to increase the amount of vitamin A stored in the body. Beta-carotene is NOT toxic to the body.

    Getting too little vitamin A can cause side effects too. Symptoms of significant deficiency include:

  • lowered resistance to infections
  • problems with getting pregnant
  • poor growth
  • improper tooth formation
  • rough, dry, and pimply skin
  • digestive problems
  • night blindness
  • eye disease, including xerophthalmia (zear-off-thal-me-ah), a condition in which the clear covering of the eye known as the cornea becomes dry and dull
  • Vitamin A is an important fat-soluble vitamin. Eat a variety of fruits, vegetables, lean meats, and fortified dairy products to ensure optimal intake of vitamin A. Read food labels to help choose foods with vitamin A content.


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    Vitamin A: Functions and Sources

    Author: Clare Armstrong, MS, RD
    Reviewer: Kathleen A. MacNaughton, RN, BSN
    Date Reviewed: 09/26/02

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