Addressing Anemia Among Adolescents in Zanzibar With School-based Supplementation of Once Weekly Iron-folic Acid or Daily Multiple Micronutrients: A Cluster-randomized Trial.

Purpose: Supplementation with iron and folic acid (IFA) is recommended by the World Health Organization; however, evidence of effectiveness in adolescents is lacking. We aimed to investigate the effectiveness of school-based supplementation of IFA or multiple micronutrient supplement (MMS) in addressing anemia among secondary schools adolescents in Zanzibar, Tanzania.

Methods: This was a nonmasked three-arm cluster-randomized trial in which 42 schools were randomized to weekly IFA, daily MMS, or control (standard nutrition curriculum). Students aged 10-17 years were supplemented for two 17-week periods, in 2022 and 2023. Hemoglobin was evaluated during four surveys conducted before and after each supplementation round. We used multilevel mixed effects models to estimate associations between study arm and anemia, categorized by World Health Organization cut points.

Results: At baseline, 2,475 students were enrolled and 53.3% had anemia, with similar prevalence across all arms. Participants in the MMS arm had 37% lower risk of moderate or severe anemia at final endline, compared to those in the control arm (risk ratio [RR] = 0 63; 95% confidence interval [CI]: 0.41, 0.99). No differences were observed in prevalence of anemia in the IFA group compared to the control group. Effects were modified by sex (p for interaction = .004), with MMS males experiencing 68% lower risk of moderate or severe anemia compared to controls (RR = 0.32; 95% CI: 0.14, 0.70), while for females the effect was smaller and not significant (RR = 0.72; 95% CI: 0.45,1.16).

Discussion: School-based supplementation with MMS may be effective in addressing anemia among adolescents; however, the specific context and appropriate complementary interventions must be considered.