Impact of consuming zinc-biofortified wheat flour on the growth and morbidity status of adolescent girls: a cluster randomised, double blind, controlled trial

Abstract

Despite the known detrimental consequences of zinc deficiency and recognized benefits of supplementation in reducing morbidity and
improving growth(1)
, programmatic zinc supplementation is not feasible(2) thus other sustainable methods such as biofortification of
staple crops to increase zinc intakes on a population scale needs to be explored. The aim of this study was to determine the effect�iveness of consuming zinc-biofortified wheat flour (Zincol-2016) on zinc-related morbidity and growth among adolescent girls, living
in a rural, marginalized community in northwest Pakistan where the prevalence of zinc deficiency is high. Households (N = 486) with
at least one adolescent girl aged 10–16 years (N = 517) near Peshawar, Pakistan were recruited to a double blind, cluster randomized
controlled trial (BiZiFED2 RCT). During phase 1 of the trial (November 2019 to September 2020), households were provided with
locally procured flour from standard wheat varieties (control) to establish a baseline. During phase 2 (September 2020 to March
2021), households received either zinc-biofortified flour or control flour. Anthropometric measurements and 24-hour dietary recalls
were collected at the beginning, middle and end of the trial(3)
. Data pertaining to incidence and duration of respiratory tract infection
(RTI) in the preceding two weeks were collected fortnightly. Analysis was performed using linear mixed models for continuous vari�ables and Pearson’s chi-square test for categorical variables. Consumption of biofortified flour contributed to a moderate increase in
estimated zinc (1.5 mg/day) and iron (1.2 mg per/day) intake. No significant effect of the intervention was observed on linear growth
(height: control 150.6 ±8.5 cms vs intervention 148.7±8.5 cms; height for age Z scores: control -0.73±1.1 vs intervention -0.92 ±1.0)
and weight (control 45.5 ±9.7 kgs vs intervention 43.4 ±10.1 kgs). Self-reported incidence of RTIs were not significantly different for
the two study arms between the baseline and midpoint, but towards the end of the trial a lower incidence of RTIs was reported in the
intervention arm compared to the control arm (week 22: control 19.3% vs. intervention 11.5%, p = 0.037; week 26: control 14.5% vs.
intervention 6.1%, p = 0.014). However, when the longitudinal prevalence of RTI (cumulative days of sickness as a percentage of total
days of observations) was considered with baseline adjustments, no treatment effects were observed (mid- point: control 10.6% [95%
CI: 8.6, 12.7] vs intervention 6.3% [95% CI: 4.9, 7.7]; endline: control 8.1% [95% CI: 6.4, 9.8] vs intervention 9.9% [95% CI: 8.0, 11.9]).
A moderate (21%) increase in dietary zinc through the consumption of zinc-biofortified flour for 25 weeks did not have a significant
effect on growth or morbidity status of adolescent girls. Longer term interventions are warranted to monitor changes in functional
outcomes in response to the ongoing national scale-up of the release of zinc- biofortified wheat varieties