The purpose of the study is determine if a plant-based resistant starch that is optimized for the individual will target the underlying cause of inflammatory bowel disease and restore a "healthier" gut microbiome in pediatric participants with inflammatory bowel disease.

Inclusion Criteria:

• Capable of giving informed consent, or if appropriate, have an acceptable representative capable of giving consent on the participant's behalf.
• Enrolled in the main parent study.
• New ulcerative colitis diagnosis (mild/moderate) or Crohn's Disease diagnosis (moderate/severe) with colonic disease with or without terminal ileum disease, already started on oral corticosteroid or aminosalicylates for induction therapy at a time following diagnostic colonoscopy.
• Clinically responsive to induction medical therapy at enrollment (Crohn's Disease participants with a weighted pediatric Crohn's Disease activity index decrease of ≥ 17.5 points or ulcerative colitis participants with a pediatric ulcerative colitis activity index decrease of ≥ 15 points).
• Ability and willingness to comply with study procedures (e.g. stool collections) for the entire length of the study.
• Willing to provide consent/assent for the collection of stool samples.

Exclusion Criteria:

• Allergy to resistant starch or excipients.
• Co-existing diagnosis with diabetes mellitus.
• Treatment with another investigational drug or intervention throughout the study.
• Current drug or alcohol dependence that, in the opinion of the site investigator, would interfere with adherence to study requirements.
• Inability or unwillingness of an individual or legal guardian to give written informed consent.
• Requirement for antibiotic therapy as part of standard Crohn's Disease therapy (i.e. those patients with penetrating disease as manifested by intra-abdominal abscess or perianal abscess).
• Requirement of oral antibiotics for other conditions (e.g. acne).
• Participant's microbiota does not produce butyrate in response to any of the assembled panel of resistant starch as measured through the Rapid Assay of an Individual's Microbiome (RapidAIM) evaluation following enrollment.
• Requirement of therapy other than oral corticosteroid / aminosalicylates for induction therapy.
• Patients diagnosed with Inflammatory Bowel Disease-Unclassified.
• Refusal to undergo follow-up colonoscopy as part of current clinical practice guidelines for Crohn's Disease standard of care.

Unblinding will occur only if necessary to ensure study participants safety, interim analysis at 5 ± 1 months, or eligibility for our associated open label trial (OARS trial). Only Dr. Mack (Co-PI) can request to break the blind for safety reasons or eligibility for the OARS Trial; only Dr Stintzi (Co-PI) will request to break the blind for interim analysis. Once the blind is broken, the patient will be discontinued from study product.