sources

{
    "link": "http://apps.who.int/iris/bitstream/10665/44110/1/9789241598019_eng.pdf",
    "retrievedDate": "23/07/2017",
    "additionalInfo": "Data on vitamin-A deficiency is based on the reported prevalence of risk by the World Health Organization, which has collated national and household level survey data on indicators extending the period 1995-2005. Note that data on vitamin-A deficiency is typically not measured on an annual basis, therefore the year of measurement will vary by country, but lie within the period 1995-2005.\n\nAll countries with a GDP per capita \u2265US$15,000 were assumed by the WHO to be free from vitamin-A deficiency of a public health significance and were therefore excluded. None of these 37 countries had retinol or night blindness data reported for either preschool-age children or pregnant women.\n\nTwo sets of indicators of VAD are commonly used for population surveys: clinically assessed eye signs and biochemically determined concentrations of retinol in plasma or serum. The incidence of night blindness in individuals indicates moderate-to-severe systemic VAD. VAD can also be identified when serum retinol concentrations fall below below a cut-off value of 0.70 \u00b5mol/l.\n\nVitamin A deficiency (VAD) is a major nutritional concern in poor societies, especially in lower income countries. Its presence as a public health problem is assessed by measuring the prevalence of deficiency in a population, represented by specific biochemical and clinical indicators of status. The main underlying cause of VAD as a public health problem is a diet that is chronically insufficient in vitamin A that can lead to lower body stores and fail to meet physiologic needs (e.g. support tissue growth, normal metabolism, resistance to infection). Deficiency of sufficient duration or severity can lead to disorders that are common in vitamin A deficient populations such as xerophthalmia (xeros = dryness; -ophthalmia = pertaining to the eye), the leading cause of preventable childhood blindness, anaemia, and weakened host resistance to infection, which can increase the severity of infectious diseases and risk of death.",
    "dataPublishedBy": "WHO. Global prevalence of vitamin A deficiency in populations at risk 1995\u20132005. WHO Global Database on Vitamin A Deficiency. Geneva, World Health Organization, 2009.",
    "dataPublisherSource": "National and household survey data extending 1995-2005."
}