Researchers from the Technical University of Munich, Germany, found that iron supplementation in patients with inflammatory bowel disease (IBD) affects the gut microbiome differently, depending on the route of administration. Intravenous iron replacement therapy might be particularly beneficial for patients with Crohn’s disease, who have an unstable gut bacterial flora.

Iron deficiency is a common problem for patients with IBD. The effects on the intestinal bacterial flora have, however, previously only been studied in mice. Alterations in the composition of bacterial species in IBD patients may exacerbate symptoms, so mapping potential changes in the gut bacterial flora could have substantial clinical implications.

The study, titled “Oral versus intravenous iron replacement therapy distinctly alters the gut microbiota and metabolome in patients with IBD,“ was a result of a collaboration between researchers at the ZIEL Institute for Food and Health at TU Munich and Canadian researchers.

“Supplying iron either orally or intravenously has a very distinct effect on the intestinal microbiota. The study shows how fragile the stability of the microbial community is, especially in patients with Crohn’s disease,” the study’s senior author, Professor Dirk Haller from TU Munich, said in a press release.

Researchers investigated effects on the gut flora after oral and intravenous administration of iron in 72 participants. The group was composed of 31 patients with Crohn’s disease, 32 with ulcerative colitis, and 19 controls with anemia but without IBD. Half of the patients received oral, and half received intravenous, iron supplementation. The research team then analyzed bacterial communities and metabolic products, as well as stool samples, from the patients.

Results, published in the journal Gut, showed that — compared to anemics serving as controls — IBD patients’ gut flora was highly sensitive to iron supplementation, particularly in those with Crohn’s disease. The team also observed that oral and intravenous iron affected the gut flora in different ways, with higher ferritin levels (an iron-storing protein) found in those treated intravenously.

During the study period, the changes in the bacterial flora were not mirrored by any changes in disease activity. The authors, therefore, concluded that short-term supplementation does not risk aggravating symptoms, but in the long run might increase the risk for exacerbations because of the instability of the bacterial flora.

“These diseases are much more complex than infections driven by commensal bacteria from the normal flora. However, we don’t know which bacteria are involved in the disease process,” Professor Haller concluded.