Objective: To determine whether long-term dietary supplementation with low doses of vitamin D helps to prevent bone loss and the development of osteoporosis or osteomalacia in out-patients with Crohn's disease.
Design: A randomized controlled study.
Setting: The out-patient clinic of a tertiary centre (university hospital).
Patients: Seventy-five out-patients (31 men and 44 women, aged 16-77 years) with Crohn's disease.
Interventions: All patients were randomly assigned to receive either an oral supplement of 1000 IU/day vitamin D for 1 year or no supplement. Bone mineral density, assessed in the distal part of the nondominant forearm using single photon absorptiometry, and serum levels of 25-hydroxyvitamin D, assessed using a competitive protein binding assay, were measured before and after the period of dietary supplementation.
Main outcome measure: Relative change of bone mineral density.
Results: Serum levels of 25-hydroxyvitamin D increased in 57% of patients who received a supplement (compared with 37% of control patients). Bone mineral density decreased significantly in control patients [median -7%, interquartile range -12.6-(+0.4%)] but not in patients who received a supplement [median -0.2%, interquartile range -3.8-(+14%); P < 0.005]. Increases in bone mineral density were especially prevalent among patients who received the supplement and had normal serum levels of 25-hydroxyvitamin D (68%), whereas increases occurred in only 18% of patients with low serum levels of 25-hydroxyvitamin D (P = 0.008). Patients without an intestinal resection and receiving the vitamin D supplement had a marginally greater increase in bone mineral content than patients who had undergone a resection (P = 0.05).
Conclusion: Long-term oral vitamin D supplementation seems to be an efficient means of preventing bone loss in patients with Crohn's disease and could be recommended, especially for patients at high risk of osteoporosis.