The Effect of Oral Iron Supplementation on Gut Microbial Composition: a Secondary Analysis of a Double-Blind, Randomized Controlled Trial among Cambodian Women of Reproductive Age.
Level 2 - randomized trial
Secondary analysis of a double-blind randomized controlled trial
PubMed 37199608 · doi:10.1128/spectrum.05273-22
What was done
This was a secondary analysis of a double-blind, randomized controlled trial evaluating the effects of 12 weeks of oral iron supplementation on gut microbial composition in Cambodian women of reproductive age. Participants received ferrous sulfate, ferrous bisglycinate, or placebo. Stool samples were collected at baseline and 12 weeks; a randomly selected subset of 172 samples across all three arms was analyzed using 16S rRNA gene sequencing and targeted real-time PCR (qPCR).
What was found
At baseline, 1% of women had iron-deficiency anemia, with Bacteroidota (45.7%) and Firmicutes (42.1%) being the dominant phyla. Iron supplementation did not change overall gut bacterial diversity. Ferrous bisglycinate increased the relative abundance of Enterobacteriaceae and showed a trend toward increased Escherichia-Shigella (no specific numbers reported). qPCR detected an increase in the enteropathogenic Escherichia coli (EPEC) virulence gene, bfpA, in the ferrous sulfate group.
Why it matters
Untargeted iron supplementation in populations that are predominantly iron-replete may promote the expansion of potentially pathogenic Enterobacteriaceae without altering overall bacterial diversity. These findings provide evidence relevant to WHO guidelines recommending blanket iron supplementation in regions with high anemia prevalence.
Limits
The study is a secondary analysis restricted to a subset (n = 172) of a larger trial. The cohort was predominantly iron-replete (only 1% iron-deficiency anemia), limiting applicability to iron-deficient populations. The abstract provides no exact numerical values, effect sizes, or p-values for taxonomic changes, and clinical endpoints (such as gastrointestinal symptoms or infection rates) were not reported.
Cited by
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