This is a randomized, double-blind placebo-controlled trial of high dose vitamin D3 at 10,000 International Units (IU) daily compared to low dose at 1000 IU daily in patients with Crohn's disease in remission.

In patients with Crohn's disease in remission, the investigators hypothesized higher doses of vitamin D would more effectively improve 25-hydroxy(OH)-vitamin D levels and would be tolerated well without side effects of hypercalcemia. The investigators also wanted to explore whether higher doses could reduce the clinical relapse rate of patients with Crohn's disease in remission, and if higher doses of vitamin D3 could improve depression and anxiety symptoms. In order to determine if there is benefit from high-dose vitamin D3, the investigators designed a pilot randomized double-blind controlled trial comparing doses of oral vitamin D3 at 10,000 IU daily to 1000 IU daily.

Inclusion Criteria:

• a prior diagnosis of Crohn's disease in clinical remission for at least 28 days with a Harvey-Bradshaw index less than or equal to 4
• All maintenance therapies for Crohn's disease will be required to be at stable dose for at least 3 months before randomization, with no systemic steroid therapy within 4 weeks.
• Vitamin D supplements will be discontinued at least 6 weeks before randomization.

Exclusion Criteria:

• Women of child bearing potential who are considering pregnancy during the study period, currently pregnant, or unwilling to use contraception to avoid pregnancy
• Participants with renal insufficiency (serum creatinine greater than 150 umol/L), sarcoidosis, hyperparathyroidism, malignancy, or any other disorder that may lead to hypercalcemia
• Patients with short-gut syndrome or a serum albumin less than 32 g/L
• Concomitant therapy with thiazide diuretics, barbiturates, digitalis, or supplemental products containing vitamin D