Impact of consuming zinc-biofortified wheat flour on the growth and morbidity status of children aged 1–5 years: a cluster-randomised, double-blind, controlled trial

Abstract

Wheat biofortification through conventional breeding and/or agronomic methods to increase zinc content may be a promising strategy for addressing zinc deficiency (Reference Gupta, Brazier and Lowe1). However, evidence on the effectiveness of zinc biofortification interventions on health outcomes are lacking. The aim of the present study was to assess the effectiveness of consuming zinc-biofortified wheat flour (Zincol-2016) on growth and zinc-related morbidity among children (aged 1–5 years), living in a rural community in northwest Pakistan.

Households (N = 486) with at least one adolescent girl aged 10–16 years and one child aged 1–5 years (N = 517) near Peshawar were recruited to a double-blind, cluster-randomised controlled trial (BiZiFED2 RCT)(Reference Lowe, Zaman and Moran2,Reference Gupta, Zaman and Fatima3) . 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 were collected at the beginning, middle and end of phase 2(Reference Lowe, Zaman and Moran2). Data pertaining to incidence and duration of respiratory tract infection (RTI) and diarrhea in the preceding two weeks were collected fortnightly. Analysis was performed using linear mixed models for continuous variables adjusted for baseline, and Pearson's chi-square test for categorical variables.

No significant effect of the intervention was observed on linear growth (height: control 2.3 ± 1.32 cm vs intervention 2.2 ± 1.41 cm; height-for-age Z scores: control -0.21 ± 0.35 vs intervention -0.21 ± 0.38) and weight gain (control 1.7 ± 1.16 kgs vs intervention 1.5 ± 0.98 kgs; weight-for-age Z scores: control 0.39 ± 0.60 vs intervention 0.29 ± 0.54). Caregiver-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 26: control 34.7% vs intervention 17.6%, p = 0.036). However, when the longitudinal prevalence of RTI (cumulative days of sickness as a percentage of total days of observations) was considered, no treatment effects were observed (mid-point: control 16.5% [95% CI: 14.1, 18.9] vs intervention 14.8% [95% CI:12.5, 17.2]; endline: control 14.0% [95% CI: 11.5, 16.4] vs intervention 12.2% [95% CI: 9.9, 14.5]). No intervention effects were reported either on the incidence of diarrhea or its longitudinal prevalence (mid-point: control 4.7% [95% CI: 3.2, 6.1] vs intervention 4.9% [95% CI: 3.5, 6.2]; endline: control 3.2% [95% CI: 2.1, 4.3] vs intervention 2.9% [95% CI: 1.6, 4.2]).

Provision of zinc-biofortified wheat flour for 25 weeks did not have a significant effect on growth or morbidity status of children. 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.