Researchers conducted a phase I pilot study to assess the feasibility of using potato starch as a dietary intervention to modify the gut microbiome in bone marrow transplant patients. The study is the first part of a two-phase ongoing clinical trial evaluating the effect of modifying the microbiome on the incidence of graft-versus-host disease (GVHD), a major complication that develops in up to half the patients who receive a bone marrow transplant and can lead to injury and death.