Effect of vitamin D3-supplementation on bone markers (serum P1NP and CTX): A randomized, double blinded, placebo controlled trial among healthy immigrants living in Norway

OBJECTIVE Vitamin D is essential for the maintenance of calcium homeostasis and bone mineralization; and low serum 25-hydroxyvitamin D (s-25-(OH)D) concentrations are associated with increased bone turnover. However, there is a lack of randomized controlled trials that have investigated the effect of vitamin D treatment on bone turnover in immigrant populations. We aimed to investigate the effect of 16-week daily vitamin D3 supplementation on bone formation marker serum procollagen type 1 amino-terminal propeptide (P1NP) and bone resorption marker C-terminal crosslinked telopeptide of type I collagen (CTX). DESIGN Double-blind, randomized, placebo-controlled trial. SETTING Immigrant community centers in Oslo, Norway. PARTICIPANTS 251 healthy adults aged 18-50 years with a non-Western immigrant background were recruited. INTERVENTION 16 weeks of daily oral supplementation with either 10 μg vitamin D3, 25 μg vitamin D3, or placebo. MAIN OUTCOME MEASURES Difference in change during the 16-week intervention between the intervention groups combined (10 or 25 μg of vitamin D3/day) and placebo, in serum P1NP and serum CTX. RESULTS A total of 214 (85%) participants completed the study. S-25-(OH)D increased from 29 nmol/L at baseline to 49 nmol/L in the intervention group with no significant change in the placebo group. However, there was no difference in change of serum P1NP (mean difference: - 1.2 μg/L (95% CI: - 5.4, 2.9, P = 0.6)) and serum CTX (mean difference: - 0.005 μg/L (95% CI: - 0.03, 0.02, P = 0.7)) between those receiving vitamin D3 supplementation compared with placebo. The plasma PTH had decreased by a mean of - 1.97 pmol/L (95% CI: - 2.7, - 1.3, P < 0.0001) in the vitamin D3 group compared to placebo. CONCLUSIONS Supplementation with 10 or 25 μg oral vitamin D3 during winter and spring for 16 weeks did not significantly affect serum P1NP and serum CTX, despite increasing s-25(OH)D and decreasing PTH in a healthy immigrant population with low baseline vitamin D status. Trial registration number: NCT01263288.