Vitamin A deficiency is one of the most common nutrient deficiency syndromes in children from developing countries. It is also correlated with the increased severity and incidence of certain
infections. Until recently,
vitamin A research was focused on preventing
xerophthalmia and
blindness in Third World Countries and on the development of synthetic
retinoid molecules, with lower toxicity than
vitamin A, for the treatment of
skin diseases. However, there has been a major shift of emphasis in the last five to ten years. There is a risk of death from
xerophthalmia, primarily from complications with
infectious diseases. Intermittent treatment with the very large doses of
vitamin A prescribed to combat
blindness was shown to be effective. This suggests that
vitamin A may affect specific elements of the immune system. High-dose
vitamin A supplements have been given, at widely-spaced time intervals, to preschool children in communities where
vitamin A deficiency causes
xerophthalmia and
blindness, over the last 20 to 30 years. A strong correlation between mortality and
xerophthalmia was identified. Death then became the principal outcome measured because it was easier to detect than
xerophthalmia, particularly in large clinical trials in high risk regions where clinical expertise was minimal and
vitamin A deficiency was a commoner cause of death than
blindness. Other, food-based approaches to the treatment and prevention of
vitamin A deficiency, involving foods naturally rich in
retinol or
carotenoid, or foods artificially fortified with these nutrients, should be developed.