Hypovitaminosis A and Epidemiology of Xerophthalmia

Abstract

The dietary intake of vitamin A activity varies from country to country both in the total activity ingested and estimated as vitamin A and the relative proportions of preformed vitamin A and its precursors. In most developing countries, carotenoids provide from 60 to nearly 100% of the total vitamin A activity ingested. Furthermore, the average per caput intake of total vitamin A activity is usually marginal or less than the requirement. The levels of serum retinol reflect the habitual dietary intake of vitamin A value. A high correlation was found between the two on comparing the data provided by the ICNND Surveys in 10 different countries. The same data have provided evidence of a correlation between serum retinol and carotenoids. However, both these relationships need to be further examined utilizing all the available data. An examination of the average serum retinol levels and their frequency distribution in populations indicates that with the average levels around 30 µg/100 ml an appreciable proportion, possibly up to 30%, have serum retinol values that are considered either “low” or “deficient” according to ICNND guidelines for interpretation of biochemical findings in nutrition surveys. When the average level is over 40 µg/l00 ml, very few individuals fall within this range. The serum retinol levels in infants and children have been discussed in the light of the occurrence of clinical vitamin A deficiency in certain developing countries. The primary condition for the occurrence of xerophthalmia is probably dietary inadequacy of vitamin A resulting in a biochemically detectable deficiency state. This forms part of general infant and child malnutrition. On this are superimposed a variety of gastrointestinal and respiratory infections. Such a situation ultimately leads to clinical vitamin A deficiency in a variable proportion of children, which may be acute or chronic. The available literature dealing with this aspect is reviewed and the findings of an epidemiological study in Jordan done by the author in 1963–1965 are briefly discussed. It is concluded that the epidemiology of xerophthalmia in infants and young children is almost identical with that of protein-calorie malnutrition, which explains their frequent association.