Vitamin A deficiency is common in the United States among low-income groups. Children are especially vulnerable because they are still growing rapidly. People who eat very-low-fat diets and who limit their consumption of liver, dairy foods and dark green vegetables, and those who experience fat malabsorption from conditions like celiac disease or infectious hepatitis can also become deficient in vitamin A. A zinc deficiency can also trigger a vitamin A deficiency by making it difficult to use the body's own stores of the vitamin.
An early warning sign of vitamin A deficiency is the inability to see well in the dark, a condition called night blindness. If the deficiency is not corrected, the outer layers of the eyes become dry, thickened, and cloudy, eventually leading to blindness if left untreated.
Vitamin A deficiency also causes dry and rough skin, making it take on a kind of "goose flesh" appearance. In addition, one can become more susceptible to infectious diseases. That's because a lack of vitamin A damages the lining of the gastrointestinal and respiratory tracts, so they can't act as effective barriers against bacteria. Infections of the vagina and the urinary tract are also more likely.
Treatment for children with xerophthalmia starts with large doses of vitamin A, decreasing to smaller amounts after a few days. Blindness can be averted if treatment is started before too much eye damage has occurred.
Diseases such as obstructive jaundice or cystic fibrosis cause poor absorption of dietary fat and the fat-soluble vitamins. So even if people with these diseases consume adequate vitamin A, they may still develop a deficiency because of poor absorption. To overcome this obstacle, patients can take large amounts of a water-soluble form of vitamin A.
A disease accompanied by prolonged fever, such as infectious hepatitis or rheumatic fever, can rapidly deplete the liver's reserves of vitamin A. As part of the treatment, a doctor may prescribe this vitamin in amounts greater than the RDA to prevent deficiency. Zinc is needed to transport vitamin A, so zinc may also be recommended at low levels.
The Recommended Dietary Allowance (RDA) for vitamin A is 900 retinol equivalents (RE) for men and 700 RE for women. Retinol equivalents are the preferred measure for vitamin A, because this method takes into account both forms of the vitamin -- retinol and carotenoids. One RE is equal to 3.33 international units (IU) of retinol or 10 IU of beta-carotene or 12 IU of mixed carotenes. Assuming you get the vitamin from both sources, the RDAs are equivalent to about 5,000 IU for men and 4,000 IU for women.
It's not necessary to obtain the RDA amount for vitamin A each day. Because vitamin A is not soluble in water, you do not excrete excess amounts of the vitamin. The liver stores vitamin A, and the body can tap into the reserves whenever dietary intake is too low. For most adults it takes months to deplete stored amounts. As long as you have a well-balanced diet that includes milk and yellow-orange and green vegetables, your overall intake should be sufficient to provide the vitamin A your body needs. Strict vegetarians, such as vegans, can obtain sufficient vitamin A if they eat a lot of pigmented vegetables.
If you choose to take vitamin A supplements to get your daily requirements, make sure you don't overdo it -- too much vitamin A can be toxic.
This information is solely for informational purposes. IT IS NOT INTENDED TO PROVIDE MEDICAL ADVICE. Neither the Editors of Consumer Guide (R), Publications International, Ltd., the author nor publisher take responsibility for any possible consequences from any treatment, procedure, exercise, dietary modification, action or application of medication which results from reading or following the information contained in this information. The publication of this information does not constitute the practice of medicine, and this information does not replace the advice of your physician or other health care provider. Before undertaking any course of treatment, the reader must seek the advice of their physician or other health care provider.