Vitamin A Deficiency

Vitamin A deficiency affects an estimated 190 million preschool-aged children and 10 million pregnant women in low-income countries. Prevalent cases of xerophthalmia in young children are believed to number ~5 million. Of these, 10% can be considered potentially blinding, such that this ocular condition remains the leading cause of preventable pediatric blindness in the developing world. Although there has been a significant decrease in the prevalence of vitamin A deficiency during the past couple of decades, vitamin A deficiency remains an underlying cause of at least 157,000 early childhood deaths due to diarrhea, measles, malaria, and other infections each year. Vitamin A deficiency is also recognized as a problem that reflects chronic dietary deficiency that may extend from early childhood into adolescence and adulthood, especially for women of child-bearing age. This chapter describes the chemical structure of vitamin A and its precursors, dietary sources, absorption, metabolism and functions, followed by discussions on the epidemiology of vitamin A deficiency, and its role in morbidity and mortality. The chapter concludes with insights on its diagnosis, treatment, and approaches to prevention through dietary improvement, supplementation, fortification, and biofortification.