“What is an appropriate dosage and interval of vitamin D2 supplementation to achieve a sufficiency level in postmenopausal women of Thailand?” A randomized, double-blind, placebo-controlled trial

ObjectiveThis study primarily evaluated serum 25-hydroxy vitamin D levels in postmenopausal women with vitamin D insufficiency who received different dosages and intervals of vitamin D2 supplementation. We secondarily evaluated the percentages of those who achieved vitamin D sufficiency level (Defined as ≥30 ng/ml).Study designRandomized double-blind, placebo-controlled trial.MethodsPostmenopausal women who met the criteria of vitamin D insufficiency (<30 ng/mL) were randomized into 4 groups (N = 25/group). Participants received a 12 week-treatment of different dosages and intervals of vitamin D2 (placebo, vitamin D2 20,000 IU/2 weeks, vitamin D2 20,000 IU/week, and vitamin D2 40,000 IU/week). Serum total 25-hydroxy vitamin D was determined at baseline, after 4 and 12 weeks of supplementation with electrochemiluminescence immunoassay (Elecys, Roche Diagnostics). Changes of 25-hydroxy vitamin D levels were compared among the groups.ResultsForty seven percent of postmenopausal women (100/212) screened for study enrolment were found to have vitamin D insufficiency. At 12 weeks, serum 25-hydroxy vitamin D increased significantly from baseline in all groups (p < 0.01) (mean serum 25-hydroxy vitamin D level increased from 23.03 ± 4.56 at baseline to 25.60 ± 4.79 ng/ml (placebo), 23.54 ± 5.14 to 27.83 ± 5.27 ng/ml (vitamin D2 20,000 IU/2 weeks), 22.68 ± 5.21 to 30.50 ± 5.14 ng/ml (vitamin D2 20,000 IU/week), and 22.88 ± 4.83 to 37.89 ± 5.47 ng/ml (vitamin D2 40,000 IU/week)). In addition, the 25-hydroxy vitamin D levels were statistically significantly different at 4 and 12 weeks (p < 0.01) among all 4 groups. The percentages of those achieving vitamin D sufficiency level after 12 weeks of supplementation were 16% (placebo), 27.3% (vitamin D2 20,000 IU/2 weeks), 44% (vitamin D2 20,000 IU/week), and 86.4% (vitamin D2 40,000 IU/week); statistically significantly different among the four groups (p < 0.01). There was no participant with 25-hydroxy vitamin D after 12 weeks of >50 ng/mL in this study.ConclusionVitamin D2 40,000 IU/week was found to be the most effective dosage for postmenopausal women in this study to achieve serum vitamin D sufficiency level.