Iron content in human milk: relationship with iron nutritional status in mother-infant dyads at six months postpartum

Abstract

Introduction: The relationship between iron content in human milk (HM) and maternal and infant iron nutritional status remains a subject of debate.

Objective: To evaluate the association between HM iron content and iron nutritional status, anemia, and iron deficiency (ID) in mothers and exclusively breastfed infants (EBF).

Materials and Methods: Observational, cross-sectional study. Iron in HM, hemoglobin, and ferritin were measured in mothers and infants attending the IDIP Health Observatory (2019–2024) at six months postpartum. Associations between HM iron and maternal/infant iron status were assessed through bivariate analyses and linear models adjusted for age, BMI, and parity. Institutional ethics approval was obtained.

Results: Seventy-nine dyads were evaluated. The prevalences of anemia and ID were 16.5% and 45.6% in mothers, and 25% and 41.0% in infants, respectively. HM iron content was 0.29 ± 0.10 mg/L, with no significant differences according to maternal or infant iron status. In both unadjusted and adjusted linear models, HM iron was not associated with hemoglobin (Beta [95% CI] mothers: 0.00 [-0.02; 0.03], p=0.863; infants: -0.73 [-2.68; 1.21], p=0.454) or ferritin (mothers: 0.00 [-0.00; 0.00], p=0.943; infants: 0.07 [-1.88; 2.03], p=0.940).

Conclusion: Human milk iron content at six months was not associated with maternal or infant iron nutritional status, suggesting that its regulation may respond to homeostatic physiological mechanisms relatively independent of maternal body iron status. This reinforces the need for iron supplementation in exclusively breastfed infants.