In the context of plant breeding and biotechnology to enhance the levels of—or improve the bioavailability of—iron, provitamin A carotenoids, and zinc to combat micronutrient malnutrition, this review discusses in detail the influence of vitamin A status on iron utilization and the consequent impact on iron status. The much less extensive literature on the interaction between vitamin A and zinc metabolism is also presented and discussed. Prior to these discussions, recent reports on the efficacy of the bioconversion of provitamin A carotenoids into retinol, and the influence of these carotenoids on vitamin A status, are presented and evaluated. An attempt is made to define the concentrations of provitamin A carotenoids that might have a significant impact on vitamin A status and to evaluate the usefulness or necessity of co-biofortifying iron- or zinc-enriched staple foods with β-carotene. Finally, knowledge gaps are identified and future research topics are proposed.
HarvestPlus Technical Monograph 6, 31 pp.