Primary Objective:

To assess how an amino acid based medical food (Enterade®) helps maintain the intestine's ability to absorb and retain fluids, leading to a reduction in diarrhea due to Neuroendocrine Tumors (NET) and/or Carcinoid Syndrome. This improvement in the absorption will be assessed in part by evaluating changes in average daily stool frequency from baseline in patients receiving Enterade®. Each subject serves as his or her own control.

Secondary Objectives:

• To assess subject reported health-related quality of life in subjects before and after compound administration.
• To characterize the side effect profile and tolerability of Enterade® as measured by the number of total 8-oz Enterade® bottles consumed throughout the trial, and average drinks per day.
• To evaluate changes in serum electrolytes before and after administration of Eenterade®.
• To assess intravenous fluid requirement and/or hospitalization for dehydration secondary to diarrhea between control observation period and active Enterade® period.
• To evaluate difference in utilization of standard-of-care anti-diarrheal medications between control observation period and Enterade® period.
• To compare subjective feeling of bloating and flatulence before and after administration of Enterade®.
• To evaluate changes in patient weight before and after administration of Enterade®.

This prospective, phase 2 study is to assess how Enterade® will affect patient-reported quality of life and intestinal absorption in patients with Carcinoid Syndrome and Neuroendocrine Tumors. The hypothesis is that Enterade® when combined with standard supportive care will improve patient-reported quality of life and help maintain the small bowel's ability to absorb and retain fluids, possibly leading to a reduction in diarrhea frequency.

• This is a non-randomized, supportive-care study.
• Potentially eligible patients will be screened in the University of Kentucky Markey Cancer Center clinics.
• During the screening visit, immediately after signing informed consent, the participant will be given both flavors of enterade® (original vanilla and refreshing orange) to test tolerability and taste.
• Eligible subjects will be given a stool diary and will be asked to document daily stool output (frequency and consistency of stool), use of anti-diarrheal medication and gastrointestinal discomforts (bloating, cramping).
• All lab and screening tests should be completed within 2 weeks prior to registration/initiation of study.
• The study is broken into 3 distinct segments and will apply to all enrolled participants: Baseline observation (Weeks 1-4), Enterade® administration period (4 weeks), Post-Enterade® Period (4 weeks).
• After relapse of diarrhea is documented or the 4 weeks of post-Enterade® observation are completed (whatever happens first), participants will be given the option to restart Enterade® for 1 additional month.

Inclusion Criteria:

• Cohort 1: Participants must have histopathologically confirmed neuroendocrine tumor with 4 or more bowel movements per day on standard anti-diarrheal regimen (which may or may not include somatostatin analogs and telotristat), AND an elevated serum serotonin or plasma serotonin above the upper limit of normal per reference lab.
• Cohort 2: Participants who have histopathologically confirmed neuroendocrine tumor and have 4 or more bowel movements per day on standard anti-diarrheal regimen (which may or may not include somatostatin analogs and telotristat), but are below the cut-point for serotonin elevation.
• Age equal to or greater than 18 years old.
• ECOG performance status ≤2 (Karnofsky ≥60%)
• Ability to tolerate thin liquids by mouth at the time of enrollment.
• Ability to understand and the willingness to sign a written informed consent document.
• Subject who are willing to take enterade® as instructed will be eligible.

Exclusion Criteria:

• Known allergy to Stevia.
• Uncontrolled intercurrent illness including, but not limited to, ongoing or active Clostridium difficile infection or history of Clostridium difficile infection.
• Participants with active clostridium difficile infection will be ineligible for this study.
• Participants with a history of inflammatory bowel disease, irritable bowel syndrome, bariatric surgery and/or Celiac disease.
• Participants with psychiatric illness/social situations that would limit compliance with study requirements.
• Patients who have had enterade® within the past 12 months.