Exploration du statut vitaminique A

Abstract

Vitamin A deficiency is still a major health issue in developing countries but remains scarce in western countries. However, vitamin A sub-deficiencies are still observed in western countries, mainly related to pathophysiological deseases (lipid malabsorption, liver diseases. . .). Seldom cases of hypervitaminosis are also observed after consumption of excessive doses of vitamin A. Signs of vitamin A deficiency or excessive intake only occur very late and early indicators for assessing abnormal vitamin A status have been elaborated. The best indicator is liver vitamin A concentration, nevertheless it is rarely used as it requires a biopsy. The mostly used indicator is blood retinol concentration, even if it is challenged because of its sensitivity to numerous factors. Indicators are based on i) clinical signs of vitamin A deficiency, e.g. hemeralopia, ii) functional methods, e.g. dark adaptative test, iii) blood and tissue molecular markers, e.g. blood retinol concentration, and iv) vitamin A load tests, e.g. relative dose response test. Interpretation of these indicators results has to be done with an acute knowledge of the sensitivity limits and the interfering factors. Choosing the adequate indicator according to the assumed vitamin A status and the expected confounding factors appears to be essential. It is also recommended to cross the results of several indicators to have a better assessment of vitamin A status.