Vitamin A may be formed in the body from the yellow pigments (containing carotene) of many fruits and vegetables, especially carrots.
Vitamin A is required for vision. Epithelial cells (those cells present in the lining of body cavities and in the skin and glands) require vitamin A.
This vitamin also required for resistance to infection.
Where it is the limiting nutrient, vitamin A deficiency causes anemia, growth retardation and xerophthalmia; increases the incidence and/or severity of infectious episodes.
Reduced survival is the most severe and potentially the most widespread consequence of vitamin A deficiency, and the one that has generated the most interest.
Vitamin A deficient animals die much earlier and at a far higher rate than vitamin A sufficient controls.
Under experimental conditions of gradual progression deficiency, mortality begins to take its toll even before the appearance of xerophthalmia.
The situation in humans is far more complex. Vitamin A deficiency rarely occurs as an isolated disturbance; when it does, it is rarely recognized in the absence of severe xerophthalmia, a condition long associated with increased mortality.
Vitamin A in general
