Vitamin A is a fat-soluble vitamin that is required for a wide range of physiological processes. Vitamin A has functions in vision, immune function, cell differentiation and proliferation, intercellular communication, reproduction, bone formation and growth. Vitamin A deficiency is associated with an increased risk of mortality from infectious diseases and is a primary cause of childhood morbidity and mortality in low-income countries. Date of preparation: January 2019.
Importance of Vitamin A for global health
Vitamin A is a fat-soluble vitamin that is required for a wide range of physiological processes including vision, immune function, cell differentiation and proliferation, intercellular communication, reproduction, bone formation and growth (1, 2). Vitamin A deficiency (VAD) is associated with an increased risk of mortality from infectious diseases and is a primary cause of childhood morbidity and mortality in low-income countries. VAD causes xerophthalmia (night blindness, Bitot’s spots, corneal ulceration and scarring), and is the leading cause of preventable blindness in children (2, 3). Night blindness has been reported during pregnancy in women in low-income countries, and is likely a consequence of marginal vitamin A status (3). WHO estimates suggest that 19 million pregnant women (15.3%) and 190 million preschool-age children (33%) were affected by VAD between 1995-2005 in countries at risk of VAD (3). More recent data suggest that the prevalence of deficiency among children 6-59 months of age in low and middle-income countries declined from 39% in 1991 to 29% in 2013; the prevalence of deficiency was highest in sub-Saharan Africa (48%) and south Asia (44%) (4). VAD tends to cluster in families and communities; vitamin A status is assumed to be inadequate in areas with documented deficiency in children and pregnant women (2).
Inadequate vitamin A intake remains common in low and middle-income countries, and is associated with poverty, limited infrastructure, food insecurity, and a high incidence of infectious diseases. Populations at risk of inadequate vitamin A intake include young children, pregnant and lactating women in low-resource settings (2).
Figure 1: Vitamin A refers to retinol, and its active metabolites (5)
Keywords: retinol, retinol binding protein, serum retinol, breast milk retinol, modified dose response, total body vitamin A stores, stable isotope, retinol isotope dilution, vitamin A, beta-carotene, provitamin A carotenoids, xerophthalmia, blindness, inflammation
Related measurements: Population coverage of vitamin A interventions (e.g. fortified foods; infant/young child high-dose vitamin A supplementation programme); population prevalence of xerophthalmia, nightblindness, measles (infection/mortality)
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