Is iron supplementation likely to impair linear growth and gut microbiota composition of Myanmar young children when complementary feeding is not optimized? A randomized controlled trial.

Clinical Snapshot

Key Findings

• P Value: Not reported in abstract

• Effect Size: Anaemia reduction: AOR 0.15 (Fe alone), 0.14 (CFRFe); Stunting increase: AOR 2.74 (Fe alone)

• Primary Outcome: Iron supplementation reduced anaemia risk (AOR 0.14-0.31) but iron alone increased stunting risk (AOR 2.74)

• Nnt Or Sensitivity: Not calculable from provided data

• Confidence Interval: Stunting AOR 2.74 (1.04-7.23); Anaemia reduction AOR 0.14 (0.07-0.31) for CFRFe

Clinical Application

Aqueous iron supplementation is feasible but should be combined with complementary feeding optimization to prevent growth impairment Limited direct applicability to Australian practice given different nutritional context, but relevant for Indigenous communities and recent migrants from similar settings Children aged 12-23 months in resource-limited settings with poor complementary feeding practices and high anaemia prevalence

Abstract

Iron deficiency, with or without anemia, remains a major public health concern among young children in Myanmar. While iron supplementation is widely recommended, its potential adverse effects on growth and gut microbiota warrant investigation, particularly in contexts of poor complementary feeding. To assess the effects of iron supplementation, with or without complementary feeding recommendations (CFRs), on micronutrient status, linear growth and gut microbiota composition among Myanmar children aged 12-23 months, a 24-week randomized controlled trial was conducted in Ayeyarwady Region of Myanmar. Fourteen clusters (villages/wards) were randomized to receive CFRs or not, and children within the clusters were randomized to receive daily aqueous iron or placebo, creating four arms: Placebo (n = 104), CFR (n = 112), Fe (n = 105) and CFRFe (n = 112) totalling 433 children. All intervention groups (CFR, Fe, CFRFe) improved haemoglobin and reduced anaemia risk compared with Placebo (AOR = 0.31 (0.15-0.62), 0.15 (0.07-0.32), 0.14 (0.07-0.31), respectively). CFR and CFRFe also improved zinc status. However, iron-alone (Fe) increased the stunting risk (AOR= 2.74 (1.04-7.23)), while CFRFe did not. No significant effects were observed on gut microbiota composition. Aqueous iron supplementation may impair linear growth when diets are not optimized; combining supplements with optimized complementary feeding may support healthier outcomes. This article is part of the theme issue 'Biological, biomedical and environmental drivers of stunting'.

References

1. 1.Hlaing, L. M., Htet, M. K., Gibson, R., Utomo, B., Firmansyah, A., & Fahmida, U. (2026). Is iron supplementation likely to impair linear growth and gut microbiota composition of Myanmar young children when complementary feeding is not optimized? A randomized controlled trial. Philosophical Transactions of the Royal Society B, 381(1234), 20250042. https://doi.org/10.1098/rstb.2025.0042