Low dose daily iron supplementation improves iron status and appetite but not anemia, whereas quarterly anthelminthic treatment improves growth, appetite and anemia in Zanzibari preschool children.

Randomized, placebo-controlled factorial trial in Zanzibari preschool children living in a malaria- and helminth-endemic setting. Active-arm groups included children aged 6-71 months with baseline hemoglobin above 70 g/L, enrolled in Kengeja village, Pemba Island, Zanzibar, United Republic of Tanzania.

This was a 2x2 factorial oral supplementation trial in which active regimens included daily ferrous sulfate providing 10 mg elemental iron for 12 months, mebendazole 500 mg chewable tablets every 3 months for 12 months, or both together. The active interventions were compared with matching placebo arms.

Overall, iron improved iron status but did not consistently improve hemoglobin or growth, while mebendazole improved appetite and showed age-specific benefits for growth and anemia. In the iron arm, ferritin increased from 30.2 to 40.7 and erythrocyte protoporphyrin fell from 162 to 106, but hemoglobin did not improve significantly overall. Mebendazole reduced mild wasting in the youngest children and reduced moderate anemia in the youngest age group; benefits were strongest under 30 months for growth and under 24 months for anemia. Both interventions improved appetite, and no iron-mebendazole interaction was detected.

Effects were age-dependent and several benefits were confined to subgroup analyses, which limits certainty. The study was conducted in one malaria- and helminth-endemic community with 12-month follow-up, so generalizability is limited. Some arm-specific outcome reporting was incomplete, and detailed dietary or physical activity confounding data were not available.