The effects of iron fortification on the gut microbiota in African children a randomized controlled trial in Cote d'Ivoire

Background Iron is essential for the growth and virulence of many pathogenic enterobacteria whereas beneficial barrier bacteria such as lactobacilli do not require iron Thus increasing colonic iron could select gut microbiota for humans that are unfavorable to the host Objective The objective was to determine the effect of iron fortification on gut microbiota and gut inflammation in African children Design In a 6 mo randomized double blind controlled trial 6-14 y old Ivorian children (n = 139) received iron fortified biscuits which contained 20 mg Fe/d 4 times/wk as electrolytic iron or nonfortified biscuits We measured changes in hemoglobin concentrations inflammation iron status helminths diarrhea fecal calprotectin concentrations and microbiota diversity and composition (n = 60) and the prevalence of selected enteropathogens Results At baseline there were greater numbers of fecal enter bacteria than of lactobacilli and bifidobacteria (P < 0 02) Iron fortification was ineffective there were no differences in iron status anemia or hookworm prevalence at 6 mo The fecal microbiota was modified by iron fortification as shown by a significant increase in profile dissimilarity (P < 0 0001) in the iron group as compared with the control group There was a significant increase in the number of enterobacteria (P < 0 005) and a decrease in lactobacilli (P < 0 0001) in the iron group after 6 mo In the iron group there was an increase in the mean fecal calprotectin concentration (P < 0 01) which is a marker of gut inflammation that correlated with the increase in fecal enterobacteria (P < 0 05) Conclusions Anemic African children carry an unfavorable ratio of fecal enterobacteria to bifidobacteria and lactobacilli which is in creased by iron fortification Thus Iron fortification in this population produces a potentially more pathogenic gut microbiota profile and this profile is associated with increased gut inflammation This trial was registered at controlled trials com as ISRCTN21782274 Am J Clin Nutr 2010 92 1406-15