Dietary Manipulation of the Microbiome-metabolomic Axis for Mitigating GVHD in Allo HCT Patients

Inclusion Criteria: * Subjects undergoing matched related and matched unrelated full intensity allogeneic HSCT. * Age ≥ 18 years for the feasibility phase. Age ≥10 years old AND ≥50 kg for the phase II portion. * Karnofsky \>70%, (Karnofsky Performance Status: an attempt to quantify cancer patients' general well-being and activities of daily life. The score ranges from 0 to 100 where 100 is "perfect" health and 0 is death.) * Subjects must be able to swallow capsules/tablets * Ability to understand and the willingness to sign a written informed consent * Willingness to consent / co-enroll on BMT long term follow up study or HUM00043287 (UMCC2001-0234) * Availability of an HLA matched related or matched unrelated donor Exclusion Criteria: * Patients with inflammatory bowel disease. * Patients with a history of gastric bypass surgery. * Patients with active Clostridium difficile infection at the time of study enrollment. Active infection is defined as a stool sample positive for Clostridium difficile toxin via EIA (enzyme immunoassay) and either symptoms (frequent loose stools) OR imaging findings consistent with toxic megacolon. * Patients actively enrolled on any other GVHD prevention trial. * Any physical or psychological condition that, in the opinion of the investigator, would post unacceptable risk to the patient or raise concern that the patient would not comply with protocol procedures.