• Provision of signed and dated informed consent form

• Stated willingness to comply with all study procedures and availability for the duration of the study

• Male or female, aged 11 - 25

• Diagnosed with Crohns Disease or Ulcerative Colitis

• Disease is in remission

‣ Adult CD (age 18-25): CDAI score \< 150

⁃ Pediatric CD (age 11-17): wPCDAI \< 12.5

⁃ Adult UC (age 18-25): Modified Mayo sub-scores: stool frequency sub-score=0, rectal bleeding sub-score=0

⁃ Pediatric UC (age 11-17): PUCAI score \< 10

• Not receiving corticosteroids

• Receiving a stable anti-TNF maintenance dose of adalimumab, infliximab, or the biosimilar infliximab-dyyb for 12 weeks prior to enrollment. A stable infliximab or infliximab-dyyb dose may range from 5 mg/kg every 8 weeks to 10 mg/kg every 4 weeks. A stable adalimumab dose may range from 20 mg every 2 weeks to 40 mg every 7 days. While therapeutic drug monitoring will not be required for inclusion, all drug and anti-drug antibody levels obtained for clinical indications within six months prior to enrollment, and from the screening visit through week 20, will be recorded.

• If receiving mesalamine, mercaptopurine, azathioprine, or methotrexate, must be on a stable dose for at least 12 weeks prior to enrollment.

• Agreement to not make any major dietary changes throughout study duration. This would include changing usual diet to a vegan diet, Specific Carbohydrate Diet (SCD), or exclusive enteral nutrition (EEN) diet.

⁃ We will include CD patients who have had one ileo-colic resection, as long as the resection did not include more of the colon than the cecum and ascending colon. CD patients may be enrolled if at least six months post-surgery.