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.