Background: Vitamin D deficiency is common in Paediatric Inflammatory Bowel Disease (PIBD) and has been implicated in disease pathogenesis and disease exacerbation. Current guidelines recommend oral vitamin D supplementation when 25OHD levels are below 50 nmol/L. Supplementation comes in two forms: either a daily supplement of a low dose of vitamin D3 (2000 IU) for several months or a single high dose of oral vitamin D3-termed 'stoss' therapy, with no consensus regarding optimum treatment.

Methods: A randomised controlled trial was conducted in children with a prior diagnosis of PIBD with 25OHD deficiency (< 50 nmol/L), comparing 2000 IU oral D3 daily to a stoss protocol (oral D3 dosage 400,000 IU for 3-12 years of age or 800,000 IU for > 12 years). Children were followed for 12 months, with biochemistry (25OHD, calcium, magnesium, phosphate, parathyroid hormone, haemoglobin, haematocrit, platelets, albumin), stool markers (calprotectin, S100A12), anthropometrics (weight, height, body mass index) as well as clinical disease indices (Paediatric Crohn's Disease Activity Index, Paediatric Ulcerative Colitis Activity Index) and medication use collected at 3, 6, 9 and 12 months.

Results: 74 children aged 5-18 years completed the study. Both 2000 IU daily and stoss protocol significantly increased 25OHD from baseline values at 3, 6, 9 and 12 months. One patient randomised to stoss protocol had a 25OHD level of 263 nmol/L with normal serum calcium. There was no difference in biochemical, stool or clinical markers between groups at any time point, nor was there any correlation between 25OHD level and calprotectin or 25OHD level and clinical disease activity scores.

Conclusions: Stoss protocol was non-inferior to 2000 IU daily vitamin D3 in raising 25OHD levels at 12 months. There was also no difference between 25OHD levels at 3, 6 and 9 months between groups.