In a recent publication in Gut, entitled 'Iron fortification adversely affects the gut microbiome, increases pathogen abundance and induces intestinal inflammation in Kenyan infants', researchers from Zurich, Nijmegen (Guus Kortman (photo), Harold Tjalsma and Dorine Swinkels; dept. Laboratory of Genetic, Endocrine and Metabolic disorders), Ede (Jos Boekhorst and Harro Timmerman), Mombasa, Nairobi and KwaZulu-Natal, analysed the effect of iron fortification on the gut microbiome of Kenyan infants.
In-home iron fortification for infants in developing countries is recommended to control anaemia but low absorption typically results in >80% of the iron passing into the colon. Iron is essential for growth and virulence of many pathogenic enterobacteria. We determined the effect of high and low dose in-home iron fortification on the infant gut microbiome and intestinal inflammation. Two double-blind randomised controlled trials were performed in 6 month old Kenyan infants (n=115) consuming home-fortified maize porridge daily for four months. In the first, infants received a micronutrient powder (MNP) containing 2.5 mg iron as NaFeEDTA or the MNP without iron. In the second, they received a different MNP containing 12.5 mg iron as ferrous fumarate or control. The primary outcome was gut microbiome composition analysed by 16S pyrosequencing and targeted real-time PCR (qPCR). Secondary outcomes included faecal calprotectin (marker of intestinal inflammation) and incidence of diarrhoea. Iron in MNPs increased enterobacteria, particularly Escherichia/Shigella (p=0.048), the enterobacteria/bifidobacteria ratio (p=0.020), and Clostridium (p=0.030). Furthermore, iron increased pathogenic E. coli strains (p=0.029) and also levels of faecal calprotectin (p=0.002). During the trial, 27.3% of infants in +12.5mgFeMNP required treatment for diarrhoea versus 8.3% in -12.5mgFeMNP (p=0.092). In this setting, provision of iron-containing MNPs to weaning infants thus adversely affects the gut microbiome, increases pathogen abundance and causes intestinal inflammation. This suggests that, until safer formulations are available, iron should be targeted to infants in need only, while providing adequate health protection.
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