Study on the effect of blood on the composition of the microbiome

Multiple studies on the microbiome have linked it's composition to the presence of various gastrointestinal diseases (colorectal cancer, IBS, Crohn's disease, etc), which have blood in the stools as one of their symptoms, but none of them has investigated the effect of blood itself on the composition of the microbiome without underlying gastrointestinal disease. We compared the microbiome of subjects undergoing iFOBT testing with and without the presence of blood in their stools that did not have any underlying diseases.