TABLE 2.
Efficacy of Daily 7000IU Vitamin D3 Supplementation in Improving Serum 25(OH)D and Related Parameters
| Time of study visit | Fixed effect of randomization* | ||||||||
|---|---|---|---|---|---|---|---|---|---|
| Baseline | 3 mo | 6 mo | 12 mo | ||||||
| n | mean ± SD | n | mean ± SD | n | mean ± SD | n | mean ± SD | LSMean ± SE | |
| 25(OH)D (ng/mL) | |||||||||
| Placebo | 28 | 17.0 ± 9.2 | 27 | 17.7 ± 9.0 | 27 | 18.4 ± 10.4 | 23 | 16.9 ± 9.3 | 17.7 ± 2.0 |
| Supplement | 30 | 18.2 ± 8.4 | 30 | 32.5 ± 13.6§,** | 30 | 29.2 ± 14.4‡,** | 27 | 28.4 ± 19.8§,¶ | 29.8 ± 1.9‡‡ |
| Free 25(OH)D (pg/mL) | |||||||||
| Placebo | 28 | 11.3 ± 7.6 | 27 | 11.4 ± 6.5 | 23 | 10.5 ± 6.2** | 10.2 ± 1.4 | ||
| Supplement | 30 | 10.3 ± 6.4 | 30 | 19.7 ± 12.4‡,** | 27 | 17.0 ± 13.1†,|| | 18.9 ± 1.3‡‡ | ||
| Bioavailable 25(OH)D (ng/mL) | |||||||||
| Placebo | 28 | 4.4 ± 3.1 | 27 | 4.5 ± 2.6 | 23 | 4.2 ± 2.3 | 4.1 ± 0.6 | ||
| Supplement | 30 | 4.1 ± 2.5 | 30 | 7.6 ± 4.7‡,** | 27 | 6.9 ± 5.9†,|| | 7.5 ± 0.6‡‡ | ||
| 1,25(OH)D (pg/mL) | |||||||||
| Placebo | 28 | 30.6 ± 10.6 | 27 | 35.9 ± 27.5 | 27 | 36.2 ± 14.5 | 23 | 33.6 ± 14.0 | 35.4 ± 2.2 |
| Supplement | 30 | 32.7 ± 11.9 | 30 | 43.1 ± 15.7** | 30 | 41.8 ± 13.1|| | 27 | 32.3 ± 10.3 | 38.9 ± 2.1†† |
| PTH (pg/mL) | |||||||||
| Placebo | 28 | 31.5 ± 16.3 | 27 | 37.5 ± 19.0 | 23 | 36.3 ± 17.7 | 37.8 ± 3.0 | ||
| Supplement | 30 | 34.2 ± 25.9 | 30 | 34.3 ± 30.4 | 27 | 42.6 ± 32.1 | 37.0 ± 2.8 | ||
Abbreviations: PTH, intact parathyroid hormone; LSMean, least square mean; 1,25(OH)D, 1,25-dihydroxyvitamin D; 25(OH)D, 25-hydroxyvitamin D.
Analytic note: Laboratory values were acquired with good reliability. For serum 25(OH)D, inter- and intra-assay coeffients of variation (CV) were <8%. Inter- and intra-assay CV were 12.6% and 9.8% for 1,25(OH)D and 2.7% and 4.3% for PTH, respectively.
Results are the fixed effect of randomization group from multilevel regression model (SAS PROC MIXED) testing for persistence of response at 3–12 months based on untransformed data, also controlling for time of study visit and adjusting for baseline values; data are LSMean ± SE. The significance of the fixed effect was assessed or confirmed based on log10-transformed data.
Significantly different from placebo mean within time of study visit by Student’s t-test at P < 0.05;
P < 0.01;
P < 0.001.
Significantly different from baseline mean within randomization group by paired t-test at P < 0.05;
P < 0.01;
P < 0.001.
Fixed effect for supplementation significantly different from placebo at P < 0.05;
P< 0.001.