Effect of vitamin D supplementation on bone and vitamin D status among Pakistani immigrants in Denmark: a randomised double-blinded placebo-controlled intervention study

Randomized, double-blind, placebo-controlled intervention study in Pakistani-origin immigrants living in Denmark with low vitamin D status. The active intervention groups included girls in early adolescence, adult women, and men, with measurements at months 0, 6, and 12.

Participants were randomized to oral vitamin D3 tablets taken daily for 12 months at either 10 mg/d or 20 mg/d, compared with placebo. The intervention aimed to raise vitamin D status in Pakistani immigrants living in Denmark.

Vitamin D3 supplementation at both 10 mg/d and 20 mg/d improved vitamin D status and lowered intact parathyroid hormone, but it did not significantly improve bone turnover markers or bone mass over the study period. Serum 25-hydroxyvitamin D rose by 31-32 nmol/L in women with both doses, by 16.5 nmol/L in men with 10 mg/d, and by 35.8 nmol/L in men with 20 mg/d; levels increased by 6 months and then remained stable. Bone findings were limited: whole-body BMC increased in men with 20 mg/d (ratio 1.01; P=0.049), while women had a small increase in whole-body BA (ratio 1.02; P=0.02) and a decrease in whole-body BMD (ratio 0.99; P=0.02). No participants developed hypercalcaemia.

The authors note limited sample size and dropout, which reduce power to detect skeletal effects. The 12-month duration may have been too short, or the dose too low, to show meaningful changes in bone outcomes, and the findings may not generalize beyond Pakistani immigrants with low vitamin D status in Denmark.