The purpose of this study is to determine whether weekly dosing of oral vitamin D3 is effective in correcting low vitamin D levels in children and adolescents with inflammatory bowel disease (also known as Crohn's disease and ulcerative colitis).

The role of vitamin D in skeletal health is well established. More recently, vitamin D has been implicated in multiple other disease states and is currently a topic of much discussion in the pediatric and adult medical literature. Individuals with gastrointestinal or hepatobiliary diseases that limit the absorption of dietary vitamin D and those individuals with limited sunlight exposure or darker skin color are at risk for suboptimal vitamin D status. Recent joint guidelines from the North American and European Societies of Pediatric Gastroenterology, Hepatology and Nutrition (NASPGHAN and ESPGHAN, respectively) have recommended routine surveillance and treatment for vitamin D insufficiency/deficiency in children affected by inflammatory bowel diseases (IBD), namely Crohn's disease (CD) and ulcerative colitis (UC). Current recommendations are for prolonged daily dosing of oral vitamin D, but studies in children with other chronic diseases have demonstrated the benefit of improved compliance with less frequent, higher doses of vitamin D. The primary goal of this pilot study is to establish whether weekly dosing of vitamin D can correct suboptimal vitamin D status in children with inflammatory bowel disease. A secondary goal is to evaluate whether pediatric IBD patients with darker skin respond differently to vitamin D therapy than do their lighter-skinned counterparts.

Inclusion Criteria:

1. Established diagnosis of inflammatory bowel disease made by a pediatric gastroenterologist and confirmed by histopathology
2. Serum 25-OH vitamin D level <30 ng/mL at time of enrollment.
3. Age 8-21 years
4. Weight > 20 kg
5. Parent, guardian, or subject (where applicable) able to give consent/assent

Exclusion Criteria:

1. Inability to ingest oral vitamin D3 capsules
2. Presence of known hepatobiliary disease
3. Presence of known kidney disease or history of renal stones
4. Use of systemic steroids within 60 days prior to enrollment.