Vitamin A deficiency usually results from inadequate intake of foods high in vitamin A (see Sources) or beta-carotene; a precursor of vitamin A.

 

In addition to dietary problems, iron deficiency and excess alcohol consumption can be causes of vitamin A deficiency.

 

Symptoms

The earliest evidence of vitamin A deficiency is impaired dark adaptation or night blindness. Mild vitamin A deficiency may result in changes in the corner of the eye. Severe or prolonged vitamin A deficiency causes changes in the cells of the clear covering of the eye (cornea) that ultimately result in corneal ulcers and blindness (3, 30). Vitamin A deficiency among children in developing nations is the leading cause of blindness (31).

 

Vitamin A deficiency is also related to immunodeficiency, diminishing the ability to fight infections. Even children who are only mildly deficient in vitamin A have a higher incidence of respiratory disease and diarrhea as well as a higher rate of mortality from infectious disease (especially measles) compared to children who consume sufficient vitamin A (32).

 

In addition, a vitamin A deficiency can cause disturbance of growth and bone formation in children and adolescents.

 

Especially in smokers, a poor supply of vitamin A can promote the development of chronic obstructive pulmonary disease (COPD), which is thought to increase the risk of cancer (33).