Estimates of vitamin A deficiency (VAD) prevalence among Zambian children vary widely. A 2009 survey in two Districts indicated that 54% of children 6-59 m were deficient (serum retinol <0.7 µmol/L). Data from 2012-13 in the same Districts yielded prevalence estimates in the 10-20% range among children 4-8 y, as well as concerns regarding excess vitamin A (VA) intakes from repeated exposure to high-dose VA supplementation (VAS) and fortified foods. We assessed whether VAS at six-monthly intervals and dietary intakes at the RDA may result in excessive accumulation of VA stores.
We used mathematical modeling to estimate total body VA stores from 6-59 m assuming: 20 µg/g liver at 6 m; liver weight = 3% body weight; median weight-for-age; dietary intakes = RDA; no VAS or full VAS course of 100,000 IU at 6 m and 200,000 IU twice annually from 12-59 m; 70% retention of supplemental and dietary vitamin A; and a fractional catabolic rate of 2.2%/d from 6-59 m.
Total body stores were consistently higher in supplemented versus non-supplemented children. However, the average change in stores within each six-month period from 6-59 m was -0.04%. VA stores remained within the 10-165 µg/g liver range (considered “normal”) with the exception of one peak at 12 m (204 µg/g liver), which returned to normal range by 13 m (129 µg/g liver).
Six-monthly VAS from 6-59 m, and adequate dietary VA intake, is unlikely to result in excessive total body VA stores in Zambian children.