“Supplying iron either orally or intravenously has a very distinct effect on the intestinal microbiota,” Professor Dirk Haller of Technical University of Munich (TUM) said in a release.
Bacterial communities were particularly sensitive to iron therapy in patients with Crohn’s disease. Crohn’s disease and ulcerative colitis are the two most common forms of chronic inflammatory bowel diseases (IBD).
“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 said.
The study shows how sensitively the gut microbiota responds to iron replacement, said Haller, who coordinated the three-month human study started at the TUM's ZIEL Institute for Food & Health (ZIEL) involving a group of international researchers.
“In this study we combined microbiome and metabolome expertise to understand the role of gut bacteria as a true intermediary between environment and the human health,” he said.
Published in the journal Gut, part of the BMJ Group, the study involved 72 participants, 53 of which had IBD (31 CD and 22 UC). In the 19-participant control group all had iron deficiency due to other causes and were non-inflamed.
Patients were randomised to receive either oral iron sulphate or intravenous (IV) iron sucrose over three months.
The oral group took one 300 mg iron sulfate tablet twice a day while IV patients received three or four separate iron sucrose 300 mg infusions if iron deficient only or with anaemia, respectively.
Faecal bacterial communities and disease activity were assessed before and after the intervention.
Both oral and intravenous iron replacement therapy improved iron balance but higher ferritin levels were seen with IV. There were marked interindividual differences in the faecal samples in IBD patients and the method of iron administration affected the bacterial communities. Crohn’s disease patients were the most susceptible to bacterial changes after iron replacement therapy.
Clinical outcomes in both administration methods were similar - the shifts in bacterial communities did not affect disease activity. The authors said IV iron therapy might specifically benefit anaemic patients with Crohn’s disease with an instable microbiota, however short term therapy may increase flare ups in IBD.
There is a high prevalence of iron deficiency in IBD patients and the standard oral iron treatment may exacerbate symptoms. Iron in the blood is tightly regulated, but regulation in the gut is unclear and both healthy and harmful bacteria may compete for iron to maintain their growth.
Published online ahead of print, doi: 10.1136/gutjnl-2015-309940
“Oral versus intravenous iron replacement therapy distinctly alters the gut microbiota and metabolome in patients with IBD”
Authors: T. Lee et al.