Effects of Zinc and Iron Supplementation on Anemia Status and Learning Concentration among Female Students: A Narrative Literature Review

Abstract

Anemia among adolescent girls remains a public health problem in Indonesia and is suspected to impair learning concentration. The national program relies on school-based iron-folic acid tablets, while the role of zinc, alone or together with iron, is unclear. This article reviews the evidence on the effects of iron and zinc supplementation on anemia status and learning concentration among female students and derives implications for future research designs. It is a narrative literature review of meta-analyses, randomized controlled trials and program documents published mainly in 2020–2026, supplemented by classic reference works. The findings indicate that (1) iron supplementation, including weekly school-based dosing, increases hemoglobin and reduces anemia; (2) zinc does not lower hemoglobin, but evidence that zinc alone corrects anemia is inconsistent, and zinc given simultaneously at high ratios can inhibit iron absorption; (3) effects on concentration are inconsistent, as an older meta-analysis reported improved attention and concentration whereas a more recent one found no significant effect on attention despite improvements in intelligence and short-term memory; and (4) evidence on combined iron and zinc for concentration outcomes in adolescent girls is almost absent, while the Indonesian zinc study identified appears to use a single-group design without a comparator. The article concludes that claims of large effects of combined iron and zinc on concentration cannot yet be sustained and proposes a three-arm cluster-randomised trial with haematological outcomes and validated concentration measures