Vitamin A deficiency usually results from inadequate intake of foods high in vitamin A (see Sources), beta-carotene or other provitamin A carotenoids; which are metabolized to vitamin A in the body.
In addition to dietary problems, excess alcohol consumption and malabsorption can be causes of vitamin A deficiency.
The earliest sign 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, xerophtalmia 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) and enphysema, which both are thought to increase the risk of lung cancer (33, 48, 49).
Authored by Dr Peter Engel in 2010, reviewed by Dr. Adrian Wyss on 31.08.2017.
