The medical importance of vitamin A and carotenoids (with particular reference to developing countries) and their determination

Vitamin A, or retinol, is an essential nutrient for man and all mammalian species since it cannot be synthesised within the body. Deficiency of the vitamin results in adverse effects on growth, reproduction and resistance to infection. The most important manifestation of severe vitamin A deficiency (VAD) is xerophthalmia, and irreversible blindness may eventually occur in one or both eyes. VAD is still an important micronutrient deficiency problem in many developing countries, afflicting large numbers of pre-school children. It is often associated with protein-energy malnutrition, parasitic infestation and diarrhoeal disease. For many communities in developing countries, the major source of vitamin A in the diet is carotenoids. These compounds are synthesised only by photosynthetic microorganisms and by members of the plant kingdom where they serve important functions in metabolism, including participating in the photosynthetic process. These pigments also provide aesthetic qualities as colourants in the plant and animal kingdoms. Most importantly, the carotenoids serve the animal kingdom as sources of vitamin A activity. Major advances have occurred in understanding the role and mechanisms of action of carotenoids. They are now thought to play specific roles in mammalian tissues relate