This clinical trial studies whether the High Fiber Program can be used to increase fiber intake in patients undergoing allogeneic hematopoietic cell transplant (HCT). Allogeneic HCT is a procedure in which a person receives blood-forming stem cells (cells from which all blood cells develop) from a genetically similar, but not identical, donor. This is often a sister or brother, but could be an unrelated donor. It is a potentially curative therapy for many conditions that affect the blood and blood-forming organs, but many patients must manage post-transplant complications, especially graft versus host disease (GVHD). GVHD occurs when the transplanted cells from a donor attack the body's normal cells causing skin rash or blisters, dry mouth, or dry eyes. The environment and health of the gut is important in allogeneic HCT patients, with an unhealthy gut environment and/or health leading to inflammation and possibly GVHD. Research has shown that diets high in fiber may improve the environment and health of the gut as well as outcomes following transplant; however, fiber intake remains low among patients. The High Fiber Program is a dietitian-led counseling program which teaches patients how to introduce high fiber foods into their diet and identify food choices and personalized strategies that will help them change their diet. The High Fiber Program may be an effective way to increase fiber intake in patients undergoing allogeneic HCT.

PRIMARY OBJECTIVES:

I. To determine the feasibility of executing the High Fiber Program in HCT patients.

II. To estimate the proportion of patients who restore fiber intake to baseline levels by day 60 post-HCT.

SECONDARY OBJECTIVES:

I. To estimate the median number of days post-HCT when allogeneic HCT (alloHCT) patients achieve baseline fiber intake levels.

II. To obtain estimates of fiber intake in the pre-HCT period and over time in alloHCT patients on the High Fiber Program.

III. To evaluate the variety of fiber sources that patients have included in their diet by day 100.

IV. To evaluate the tolerability of introducing fiber into patients' diets based on when patients resume fiber intake post-transplant and the frequency of medications for controlling gastrointestinal symptoms.

V. To characterize toxicities associated with introducing fiber into patients' diets.

VI. To evaluate the median day of onset of acute GVHD and cumulative incidence of grade 2 or higher acute graft-versus (vs)-host disease (GVHD), per Mount Sinai Acute Graft Versus Host Disease International Consortium Grading System (MAGIC) criteria, at day +100 post-HCT, including incidence and severity of lower gastrointestinal acute GVHD.

VII. To evaluate incidence and severity of infections per Blood and Marrow Transplant Clinical Trials Network (BMT CTN) criteria, including bloodstream infections, up to day 100.

VIII. To obtain estimates of correlation between fiber intake and quality of life scores at day 100 post-HCT.

IX. To estimate the proportion of patients who achieve a fiber intake of at least 25g on at least one day by day 100 post-HCT.

X. To evaluate the cumulative incidence of chronic GVHD at 180 days, 1 year and 2 years post-HCT in patients on the High Fiber Program.

XI. To estimate overall survival (OS) and cumulative incidence of relapse/progression and non-relapse mortality at 100 days, 1 year and 2 years post-HCT in patients on the High Fiber Program.

EXPLORATORY OBJECTIVES:

I. To assess the feasibility of obtaining patient reported side effects and medications for symptom relief during the pre-screening period.

II. To assess how fiber intake influences immune reconstitution pattern over the course of therapy.

III. To evaluate how fiber intake relates to fecal/intestinal microbiome composition over the course of therapy.

IV. To assess relationships between fiber intake and serum inflammatory cytokines over the course of therapy.

V. To assess relationships between fiber intake and acute GVHD biomarkers, especially Reg3a produced by intestinal enterocytes.

VI. To evaluate how fiber intake relates to fecal metabolite levels over the course of therapy.

VII. To evaluate whether fiber intake relates to calorie intake over the course of therapy.

OUTLINE:

Patients attend five or six High Fiber Program dietitian-lead counseling sessions up to 30 days and/or 18 days prior to scheduled HCT, upon admission to inpatient care, at discharge, at day 42 post-transplant (approximately 20-30 days post-discharge), and at day 60 post-transplant. Patients also meet with High Fiber Program dietitian once a week (QW) and select food options from Fiber Aware Menu during admission. Additionally, patients receive a study booklet and undergo blood sample collection on study.

After completion of study intervention, patients are followed up on days 72, 100, and 180 and years 1 and 2.

Inclusion Criteria:

• PRE-SCREENING INCLUSION: Documented informed consent of the participant and/or legally authorized representative

• PRE-SCREENING INCLUSION: Age: ≥ 18 years

• PRE-SCREENING INCLUSION: Within healthy body mass index (BMI) range 18-29 at the time of pre-screening consent

• PRE-SCREENING INCLUSION: Ability to read and understand English for questionnaires

• PRE-SCREENING INCLUSION: Patients must be scheduled to receive HCT within the next 30 days after pre-screening consent

• MAIN INCLUSION: Documented informed consent of the participant and/or legally authorized representative

• MAIN INCLUSION: Age: ≥ 18 years

  • Patients ≥ 75 years of age that are otherwise eligible to undergo allogeneic HCT are included

• MAIN INCLUSION: Karnofsky performance status ≥ 70%

• MAIN INCLUSION: Within healthy BMI range 18-29 at the time of consent

• MAIN INCLUSION: Ability to read and understand English for questionnaires

• MAIN INCLUSION: Patients receiving myeloablative or reduced intensity conditioning regimens

• MAIN INCLUSION: Adequate organ function consistent with institutional standards for HCT

• MAIN INCLUSION: Patients must be scheduled to receive HCT within 3 weeks of consent

• MAIN INCLUSION: Women of childbearing potential (WOCBP): negative urine or serum pregnancy test (within 45 days prior to the start of conditioning)

  • If the urine test is positive or cannot be confirmed as negative, a serum pregnancy test will be required

• MAIN INCLUSION: Agreement by females and males of childbearing potential to use an effective method of birth control or abstain from heterosexual activity for the course of the study through at least 6 months post-HCT

  • Childbearing potential defined as not being surgically sterilized (men and women) or have not been free from menses for > 1 year (women only)

Exclusion Criteria:

• PRE-SCREENING EXCLUSION: Clinically significant uncontrolled illness
• PRE-SCREENING EXCLUSION: Active infection requiring antibiotics
• PRE-SCREENING EXCLUSION: History of chronic gastrointestinal conditions such as inflammatory bowel disease or Crohn's disease
• PRE-SCREENING EXCLUSION: Medical contraindications to incorporating fiber in their diet as determined by the treating physician
• PRE-SCREENING EXCLUSION: Self-reported major dietary restrictions limiting fiber intake
• PRE-SCREENING EXCLUSION: Any other condition that would, in the investigator's judgment, contraindicate the patient's participation in the clinical study due to safety concerns with clinical study procedures
• PRE-SCREENING EXCLUSION: Prospective participants who, in the opinion of the investigator, may not be able to comply with all study procedures (including compliance issues related to feasibility/logistics)
• MAIN EXCLUSION: Clinically significant uncontrolled illness
• MAIN EXCLUSION: Active infection requiring antibiotics
• MAIN EXCLUSION: History of chronic gastrointestinal conditions such as inflammatory bowel disease or Crohn's disease
• MAIN EXCLUSION: Medical contraindications to incorporating fiber in their diet as determined by the treating physician
• MAIN EXCLUSION: Self-reported major dietary restrictions limiting fiber intake
• MAIN EXCLUSION: Any other condition that would, in the investigator's judgment, contraindicate the patient's participation in the clinical study due to safety concerns with clinical study procedures
• MAIN EXCLUSION: Prospective participants who, in the opinion of the investigator, may not be able to comply with all study procedures (including compliance issues related to feasibility/logistics)