From kernel to consumer: bridging molecular breeding and nutritional delivery in provitamin A maize through the delivered retinol activity equivalents (dRAE) framework

Purpose The purpose of this review is to examine how provitamin A accumulation in maize, post-harvest retention, food processing, carotenoid bioavailability and host-specific bioconversion collectively influence vitamin A delivery, and to propose the delivered retinol activity equivalent (dRAE) framework for scenariobased assessment. Vitamin A deficiency (VAD) remains a major global public health problem, particularly in populations reliant on staple-based diets. Provitamin A (PVA)-biofortified maize has emerged as a sustainable food-based intervention to improve vitamin A intake. Design/methodology/approach This study integrates current knowledge on the molecular basis of PVA accumulation, carotenoid stability, post-harvest retention and host factors affecting vitamin A utilization. Literature was collected from Web of Science, Scopus and PubMed using keywords related to PVA maize breeding, processing, storage and bioavailability. Priority was given to recent peer-reviewed high-quality studies reporting evidence on PVA concentration, carotenoid retention, bioavailability and bioconversion. Findings Molecular breeding has increased kernel ß-carotene through key carotenoid pathway genes, including lcyE and crtRB1. However, kernel carotenoid concentration alone does not ensure effective vitamin A delivery. Post-harvest degradation during storage, processing and cooking, together with dietary and physiological factors, can substantially influence carotenoid availability and conversion to retinol. Host genetic variability, particularly polymorphisms in BCMO1, further contributes to differences in ß-carotene conversion efficiency. Practical implications The dRAE framework provides a conceptual, scenario-based approach for considering crop composition, post-harvest retention, bioavailability and bioconversion together when evaluating the potential vitamin A contribution of PVA-biofortified maize. Originality/value Effective vitamin A delivery from PVA-biofortified maize depends on kernel carotenoid concentration, post-harvest retention, bioavailability and bioconversion. The authors propose a delivery-oriented framework, Delivered Retinol Activity Equivalent (dRAE), to integrate these factors under specified conditions.