change in study design before recruitment began

Inflammatory bowel disease (IBD), which includes ulcerative colitis (UC) and Crohn's disease (CD), are chronic relapsing inflammatory conditions of the gastrointestinal tract. IBD is thought to result from a complex interaction between genetic, immune, microbial and environmental factors. There is emerging data suggesting Vitamin D may not only play a role in bone health but may also be involved in gut health as well. While there are guidelines regarding the recommending doses of Vitamin D for supplementation and maintenance in bone health, these strategies are unknown in those with inflammatory bowel disease. The investigators seek to determine a dosing strategy for this population using doses within the recommended guidelines for bone health.

Inflammatory bowel disease (IBD), which includes ulcerative colitis (UC) and Crohn's disease (CD), are chronic relapsing inflammatory conditions of the gastrointestinal tract. IBD is thought to result from a complex interaction between genetic, immune, microbial and environmental factors. The role of vitamin D in bone health and calcium homeostasis is well documented. However, emerging data suggests that vitamin D may also regulate immune responses, which may play a role in the pathogenesis and disease activity of IBD.

The investigators seek to identify CD or UC patients with mild disease or in clinical remission who have vitamin D levels <30 ng/ml and not on any type of vitamin repletion therapy. The investigators will randomize the participants into one of four arms: (1) Oral 50,000 vitamin D IU every week for 12 weeks (2) Oral 50,000 vitamin D weekly for 12 weeks than oral 800 vitamin D IU/d (3) Oral 50,000 vitamin D IU weekly for 12 weeks then 5,000 vitamin D IU/d (4) Oral 5,000 vitamin D IU/d and check vitamin D levels and inflammatory markers as part of standard of care follow- up every 3 months for nine months. Every participant will receive dietary counseling throughout the study duration. Our aim is to identify an optimal dosing strategy for repletion and maintenance of vitamin D levels in the subset of IBD patients. Based on clinical experience, doses higher than the recommended doses for bone health are needed to achieve and maintain optimal levels of Vitamin D in IBD patients, even patients are in remission or do not have small bowel (malabsorption) involvement.

Inclusion Criteria:

1. Diagnosis of Crohn's disease or Ulcerative colitis
2. In clinical remission or with mild disease activity as determined by the Harvey Bradshaw Index (CD) ≤7 or Ulcerative Colitis disease activity index ≤6.
3. 25(OH)D level <30 ng/ml within three months of study enrollment
4. Provided verbal consent
5. 18 years of age or older

Exclusion Criteria:

1. Unwilling to provide consent or lack capacity
2. Moderate to severe disease activity (Harvey Bradshaw index >7 or UCDAI >6)
3. Current pregnancy or attempting to conceive
4. Known coexisting hyperparathyroidism
5. Already on vitamin D supplementation, calcium supplementation or a multivitamin
6. BMI >30 kg/m²
7. History of kidney stones
8. Subjects <18 years of age - pediatric population with different recommended dosing than adults (10).
9. Non-english speakers