Vitamin A and Vitamin A Deficiency

Vitamin A is an essential factor for development, growth, health and survival. Vitamin A (retinol, 1) and its chemically and metabolically related forms retinal (2) and retinoic acid (3) play essential roles in such diverse processes as vision and cell regulation. The role of retinal as the chromophore of the visual pigments such as rhodopsin has been investigated intensively and is summarized in Volume 4, Chapter 15. It is well understood, therefore, why prolonged deficiency of vitamin A can lead to reversible night blindness that may be followed by irreversible loss of sight. It is also well understood that vitamin A is a factor in maintaining immunocompetence and that retinoic acid is an essential hormone-like factor in regulation of gene expression in relation to growth and development. Not surprisingly then, vitamin A deficiency (VAD) can have very serious consequences. Although much of this book deals with those aspects of nutrition and health that are of most concern in richer countries where food is plentiful, we must not forget that ensuring adequate supplies of vitamin A or provitamin A in poor countries to prevent the scourge of vitamin A deficiency remains the most important life-or-death aspect of carotenoids and health. To lose sight of this fact is unforgivable. Open image in new window