Effect of vitamin D 3 -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.