Maintenance Dosing of Vitamin D in Crohn's Disease

The investigators seek to identify patients with Crohn's disease in clinical remission who have vitamin D levels \<30 ng/ml. Subjects will undergo a 8 week lead in period and receive Vitamin D supplementation with 50,000 IU D2 weekly for 8 weeks.Participants with sufficient Vitamin D levels after 8 weeks (\>30 ng/mL) will be enrolled into the study and randomized to one of three arms: (1) placebo (2) 1000 IU/day Vitamin D3 (3) 5,000 IU/day Vitamin D3 for 22 weeks. Based on clinical experience, doses higher than the recommended doses for bone health in the general population (600-800 IU/day Vitamin D3) are needed to achieve and maintain optimal levels of Vitamin D in people with Crohn's disease. The investigators aim to determine optimal maintenance dosing to sustain vitamin D sufficiency in people with Crohn's disease. The investigators also seek to determine demographic and disease related characteristics associated with inability to maintain sufficient levels.