Iron supplementation and six-month hemoglobin in Peruvian children: a dose-response analysis

Introduction: Hematological response to iron supplementation in young children is variable, and the precise number of effective doses remains undetermined. Objective: To evaluate the dose-response relationship between the number of iron supplementations and hemoglobin levels at six months in children under 36 months. Methods: Analytical study using secondary data from 4,781 children under 3 years from Junín (Peru), with available measurements of baseline and six-month hemoglobin. The exposure was the total number of supplementations (0-6 doses). ANOVA and Kruskal–Wallis tests were used for comparisons across categories, and a generalized additive model (GAM) with penalized splines was applied to estimate the nonlinear relationship between supplementation and Hb6, adjusting for baseline age. Results: The GAM showed a significant nonlinear effect for the number of doses (p = 0.015). The curve exhibited a nonlinear trend, with a progressive increase from approximately 3 doses and relative stabilization around 5-6 doses. Group comparisons showed small but statistically significant differences (p < 0.01). Conclusion: Iron supplementation showed a nonlinear association of limited magnitude with six-month hemoglobin levels.