Global Iron and Zinc Biofortification for Hidden Hunger: Current Deployment, Evidence, Scaling Constraints and Priorities

Abstract

Iron and zinc deficiencies remain major components of hidden hunger, particularly where diets are dominated by staple foods and access to diverse, nutrient-dense foods is constrained. Biofortification seeks to increase the micronutrient value of crops during plant growth through conventional breeding, agronomic management and, increasingly, advanced biotechnological approaches. This critical narrative review evaluates the present status of global iron and zinc biofortification initiatives, with emphasis on the distinction between crop release, seed availability, consumption, micronutrient delivery and demonstrated nutritional benefit. Literature published from 2000 to 13 June 2026 was examined across accessible scholarly indexes and authoritative programme sources, with earlier evidence considered when necessary to interpret foundational developments. The evidence is strongest for iron-biofortified beans, pearl millet and rice in controlled efficacy settings, where improvements in ferritin, body iron or related functional outcomes have been demonstrated in populations with low iron status. For zinc, isotope and absorption studies establish biological plausibility and improved absorbed zinc from enriched staples, while several effectiveness trials have not detected corresponding changes in plasma zinc, highlighting limitations of biomarkers, exposure contrasts and implementation fidelity. Agronomic zinc biofortification can raise cereal grain zinc rapidly, especially with foliar or combined soil–foliar fertilisation, but requires recurrent inputs and remains sensitive to soil, genotype and management. Breeding-based delivery offers lower recurrent costs after varietal mainstreaming but depends on seed systems, trait retention, processing and consumer demand. Global initiatives now span multiple staple crops and regions, yet evidence of population-level nutritional impact remains much thinner than evidence of varietal release. The central policy implication is that biofortification should be judged by a delivery cascade from nutrient target to habitual intake and health-relevant outcome, and should complement rather than displace supplementation, food fortification and dietary diversification. Future programmes require standardised nutrient thresholds, traceable coverage metrics, stronger post-release surveillance and pragmatic nutrition trials linked to seed and food-market systems.