Impact of Provitamin a Biofortified Maize Flour Consumption on Dark Adaptation in Zambian Children

Abstract

Objectives: Approximately one third of children in developing countries are deficient in vitamin A (VA). Of these, 5.2 million are affected by night blindness—a severe impairment in dark adaptation. ProVA biofortified “orange” maize has been introduced in Africa as a potential intervention to address VA deficiency. We tested the impact of regular orange maize flour consumption on dark adaptation in preschool-aged children. Methods: This was a cluster-randomized trial of children aged 4-8 years (n=1,024; 50 clusters) in Mkushi, Zambia comparing orange maize to conventional white maize. A random subsample (n=542) was assessed pre- and post-intervention using a portable field dark adaptometer to record pupillary response to varying light stimuli (-2.9 to 0.1 c/m2). We measured pre- and post-stimuli pupil diameter using Tracker video analysis software and calculated the % change (i.e., “responsiveness”). Pupillary threshold was defined as the lowest stimulus causing a ≥20% reduction in pupil diameter. Results: At baseline, children assigned to orange maize were less responsive than those in the white group to all light stimuli. After the six-month intervention, pupillary responsiveness in the orange group improved across all stimuli. No consistent changes in responsiveness were observed in the white group. Pupillary threshold scores improved in 47% of orange group children versus 35% in the control arm. Improvements were more pronounced among children who consumed >75% of the maize meal provided, compared to those with lower compliance. Conclusions: Regular consumption of proVA biofortified maize flour improved dark adaptation in a marginally VA deficient population.