Adequate vitamin A intake is important for maintaining good health and preventing disease. Vitamin A helps in the formation and maintenance of healthy teeth, skeletal and soft tissue, mucous membranes and skin. Also known as retinol, it generates pigments necessary for the retina to function properly and promotes good vision. One of vitamin A's most important properties is that it acts as an antioxidant and therefore boosts the immune system.
Abnormalities also appear in the eyes of vitamin A deficient children. In the mildest form, night blindness occurs because the rods in the eye no longer produce rhodopsin, a pigment essential for seeing in the dark. In more severe forms, lesions occur on the conjunctiva and the cornea that if left untreated can cause irreversible damage, including partial or total blindness.
Xerophthalmia is a term used to cover all the ocular manifestations of vitamin A deficiency, including not only the structural changes affecting the conjunctiva, cornea and occasionally the retina, but also the biophysical disorders of retinal rod and cone function that are attributable to vitamin A deficiency. Xerophthalmia, while clearly not synonymous with blindness resulting from vitamin A deficiency, does denote an advanced degree of vitamin A depletion which constitutes a potential threat to sight. Vitamin A deficiency, of necessity, includes xerophthalmia but has much wider implications. It relates to any state in which the vitamin A status is subnormal. Although this is not capable of precise definition, it can be presumed to occur when the habitual intake of total vitamin A is markedly below the recommended dietary intake (RDI).
Vitamin A is found as retinol in breastmilk, liver, eggs, butter and whole cow's milk. Carotene, a precursor of vitamin A that is converted to retinol in the abdominal walls, is found in green leafy vegetables, orange and yellow fruits, and red palm oil.
Vitamin A deficiency and xerophthalmia are among the most widespread and serious nutritional disorders that affect humankind. For many years the problem has remained unchecked and continued to exact a devastating toll in blindness and death among young children. Vitamin A deficiency is widespread, clinically affecting 100 million pre-school-age children worldwide. Because Vitamin A is essential for the functioning of the immune system, children who are vitamin A deficient are at much greater risk of dying from common childhood illnesses such as measles and malaria. More than half a million children become blind every year through Vitamin A deficiency, and two-thirds of them die within weeks. Vitamin A can improve a child's chance of survival by as much as 25%. UNICEF claims that deficiency of vitamin A may cause one of every four child deaths in regions where it is prevalent.
The regions most affected by vitamin A deficiency are Africa, South Asia, East Asia and the Pacific, Latin America and the Caribbean and the Middle East. Serious deficiencies in vitamin A have been reported in the following countries:
[Africa]
Angola, Benin, Burundi, Burkina Faso, Chad, Ethiopia, Ghana, Kenya, Malawi, Mali, Mauritania, Mozambique, Niger, Nigeria, Sudan, Tanzania UR, Uganda, Zambia.
[America]
Bolivia, Brazil, El Salvador, Haiti, Mexico.
[Asia]
Afghanistan, Bangladesh, Burma, India, Indonesia, Kampuchea Dem, Laos, Nepal, Oman, Philippines, Sri Lanka, Vietnam.