Table 2.

Randomized Vitamin D Trials Outlining the Relation Between Vitamin D Metabolites and Bone Health Outcomes

Article InterventionNAge Gender RaceRelation to total 25(OH)DRelation to PTHRelation to calcium + BTM + BMDAssayFormula for calculated 25(OH)DRanges of vitamin D level
Sollid et al, 2016 (27)472Age 62 years on averageMeasured free 25(OH)DTotal 25(OH)DTotal 25(OH) D by LC-MSVermeulen’s equationTotal 25(OH)D ~ 63 ± 22 nmol/L, 25.2 ± 8.8 ng/mLCalculated free 25(OH) D 20 ± 7.4 pmol/L, 8 ± 2.96 ng/L
Intervention: 20,000 IU/weekMale/Female 293/179r = 0.73, Sr = −0.21*Free 25(OH) D by ELISAMeasured free 25(OH)D 13.4 ± 4.2 pmol/L, 5.36 ± 1.68 ng/L
OR 2857 IU/day for 12 mosCalculated free 25(OH)DMeasured Free 25(OH)DCalculated bioavailable 25(OH)D 8.5 ± 3.1 nmol/L, 3.4 ± 1.24 μg/L
* no r providedr = −0.17*After supplementation:
Total 25(OH)D ~ 109 ± 26.2 nmol/L, 43.6 ± 10.48 ng/mL
Calculated free 25(OH)D 36.9 ± 9.4 pmol/l, 14.7 ± 3.7 ng/L
Measured free 25(OH)D 21.9 ± 5.2 pmol/L, 8.7 ± 2.08 ng/L
Yao et al, 2017 (45)448Age 30 years on averageBaseline bioavailable 25(OH)DSupplementation Total 25(OH)D and Bioavailable 25(OH)D*, r not providedBioavailable 25(OH) D and Calcium, r = 0.11*Total 25(OH) D by LC-MSVermeulen’s equationTotal 25(OH)D 32.8 nmol/L, 13.2 ± 3.52 ng/ mL
Intervention: 2000 IU/day for 20 weeksMale/ Female 141/307NSBioavailable 25(OH)D 2.7 ± 0.8 nmol/L, 1.08 ± 0.32 μg/L
Supplementation Bioavailable 25(OH)D*, no r providedAfter supplementation:
Total 25(OH)D 67.3 ± 23.1 nmol/L, 26.92 ± 9.24 ng/mL
Bioavailable 25(OH)D 3.0 ± 3 nmol/L, 1.2 ± 1.2 μg/L
Smith et al, 2019 (38)358Older women:Baseline free 25(OH) D, S, r = 0.73Total and measured free 25(OH)D*Total 25OHD by LC-MSTotal 25 (OH)D ~ 50.9 ± 13.2 nmol/L, 20.36 ± 5.28 ng/mL
Intervention: 400 to 4800 IU/day for 12 mosAge 66 years on averageSupplementation free 25(OH)D r = 0.86*Free 25(OH) D measured by ELISAFree 25 (OH)D ~ 9.21 ± 2.88 nmol/L, 3.68 ± 1.15 ng/L
Caucasian 140 (62%)
African American 88 (38%)
Younger women:
Age 37 years on average
Caucasian 91(70%)
African American 39 (30%)
Meryl LeBoff et al, 2020 (48)771Age 63 years on averagepQCT
percent change, NS
Total 25(OH) D by LC-MSTotal 25(OH)D 69.1 ± 22.7 nmol/L, 27.64 ± 9.08 ng/mL
Intervention: 2000 IU/ day for 2 yearsMale/ Female: 411/360Free 25(OH) D by ELISAFree 25(OH)D 14.6 ± 4.7 pmol/L, 5.9 ± 1.88 ng/L
White 630, Black 67, Hispanic 26, Asian 15After supplementation:
Native American or Alaskan native 5Total 25(OH)D 98.6 nmol/L, 39.44 ng/mL
Free 25(OH)D 22.3 pmol/L, 8.92 ng/L
Aspray et al, 2019 (47)379Age 74 years on averageTotal and measured free 25(OH)D, S, no rChange in BMD, NSTotal 25 (OH)D by LC-MSMathematical modelTotal 25(OH)D 41.6 ± 19.9 nmol/L, 16.64 ± 7.96 ngl/mL
Intervention: 12,000, 24,000, 48,000 IU/ mo for 12 mos,Male/ Female: 260/112Free 25(OH)D 8.7 ± 4.2 pmol/L, 3.48 ± 1.68 ng/L
Equivalent to 400 IU/ day, 800 IU/day, 1600 IU/day
After supplementation:
Total 25(OH)D [55.0-79] nmol/L, [22-31.6] ng/mL
Free 25(OH)D [11.7-16.8] pmol/L, [4.68-6.72] ng/L
Article InterventionNAge Gender RaceRelation to total 25(OH)DRelation to PTHRelation to calcium + BTM + BMDAssayFormula for calculated 25(OH)DRanges of vitamin D level
Sollid et al, 2016 (27)472Age 62 years on averageMeasured free 25(OH)DTotal 25(OH)DTotal 25(OH) D by LC-MSVermeulen’s equationTotal 25(OH)D ~ 63 ± 22 nmol/L, 25.2 ± 8.8 ng/mLCalculated free 25(OH) D 20 ± 7.4 pmol/L, 8 ± 2.96 ng/L
Intervention: 20,000 IU/weekMale/Female 293/179r = 0.73, Sr = −0.21*Free 25(OH) D by ELISAMeasured free 25(OH)D 13.4 ± 4.2 pmol/L, 5.36 ± 1.68 ng/L
OR 2857 IU/day for 12 mosCalculated free 25(OH)DMeasured Free 25(OH)DCalculated bioavailable 25(OH)D 8.5 ± 3.1 nmol/L, 3.4 ± 1.24 μg/L
* no r providedr = −0.17*After supplementation:
Total 25(OH)D ~ 109 ± 26.2 nmol/L, 43.6 ± 10.48 ng/mL
Calculated free 25(OH)D 36.9 ± 9.4 pmol/l, 14.7 ± 3.7 ng/L
Measured free 25(OH)D 21.9 ± 5.2 pmol/L, 8.7 ± 2.08 ng/L
Yao et al, 2017 (45)448Age 30 years on averageBaseline bioavailable 25(OH)DSupplementation Total 25(OH)D and Bioavailable 25(OH)D*, r not providedBioavailable 25(OH) D and Calcium, r = 0.11*Total 25(OH) D by LC-MSVermeulen’s equationTotal 25(OH)D 32.8 nmol/L, 13.2 ± 3.52 ng/ mL
Intervention: 2000 IU/day for 20 weeksMale/ Female 141/307NSBioavailable 25(OH)D 2.7 ± 0.8 nmol/L, 1.08 ± 0.32 μg/L
Supplementation Bioavailable 25(OH)D*, no r providedAfter supplementation:
Total 25(OH)D 67.3 ± 23.1 nmol/L, 26.92 ± 9.24 ng/mL
Bioavailable 25(OH)D 3.0 ± 3 nmol/L, 1.2 ± 1.2 μg/L
Smith et al, 2019 (38)358Older women:Baseline free 25(OH) D, S, r = 0.73Total and measured free 25(OH)D*Total 25OHD by LC-MSTotal 25 (OH)D ~ 50.9 ± 13.2 nmol/L, 20.36 ± 5.28 ng/mL
Intervention: 400 to 4800 IU/day for 12 mosAge 66 years on averageSupplementation free 25(OH)D r = 0.86*Free 25(OH) D measured by ELISAFree 25 (OH)D ~ 9.21 ± 2.88 nmol/L, 3.68 ± 1.15 ng/L
Caucasian 140 (62%)
African American 88 (38%)
Younger women:
Age 37 years on average
Caucasian 91(70%)
African American 39 (30%)
Meryl LeBoff et al, 2020 (48)771Age 63 years on averagepQCT
percent change, NS
Total 25(OH) D by LC-MSTotal 25(OH)D 69.1 ± 22.7 nmol/L, 27.64 ± 9.08 ng/mL
Intervention: 2000 IU/ day for 2 yearsMale/ Female: 411/360Free 25(OH) D by ELISAFree 25(OH)D 14.6 ± 4.7 pmol/L, 5.9 ± 1.88 ng/L
White 630, Black 67, Hispanic 26, Asian 15After supplementation:
Native American or Alaskan native 5Total 25(OH)D 98.6 nmol/L, 39.44 ng/mL
Free 25(OH)D 22.3 pmol/L, 8.92 ng/L
Aspray et al, 2019 (47)379Age 74 years on averageTotal and measured free 25(OH)D, S, no rChange in BMD, NSTotal 25 (OH)D by LC-MSMathematical modelTotal 25(OH)D 41.6 ± 19.9 nmol/L, 16.64 ± 7.96 ngl/mL
Intervention: 12,000, 24,000, 48,000 IU/ mo for 12 mos,Male/ Female: 260/112Free 25(OH)D 8.7 ± 4.2 pmol/L, 3.48 ± 1.68 ng/L
Equivalent to 400 IU/ day, 800 IU/day, 1600 IU/day
After supplementation:
Total 25(OH)D [55.0-79] nmol/L, [22-31.6] ng/mL
Free 25(OH)D [11.7-16.8] pmol/L, [4.68-6.72] ng/L

Values for 25(OH) D levels in italics provide values using units similar to ones in our study for ease of comparability, values of vitamin D metabolites correspond to values at baseline unless specified otherwise.

* indicates significance

Abbreviations: 25(OH)D, 25-hydroxyvitamin D; BMD, bone mineral density; BTM, bone turnover marker; LC-MS, liquid chromatography–mass spectrometry; NA, not available; NS, not significant; pQCT, peripheral quantitative computed tomography.

Table 2.

Randomized Vitamin D Trials Outlining the Relation Between Vitamin D Metabolites and Bone Health Outcomes

Article InterventionNAge Gender RaceRelation to total 25(OH)DRelation to PTHRelation to calcium + BTM + BMDAssayFormula for calculated 25(OH)DRanges of vitamin D level
Sollid et al, 2016 (27)472Age 62 years on averageMeasured free 25(OH)DTotal 25(OH)DTotal 25(OH) D by LC-MSVermeulen’s equationTotal 25(OH)D ~ 63 ± 22 nmol/L, 25.2 ± 8.8 ng/mLCalculated free 25(OH) D 20 ± 7.4 pmol/L, 8 ± 2.96 ng/L
Intervention: 20,000 IU/weekMale/Female 293/179r = 0.73, Sr = −0.21*Free 25(OH) D by ELISAMeasured free 25(OH)D 13.4 ± 4.2 pmol/L, 5.36 ± 1.68 ng/L
OR 2857 IU/day for 12 mosCalculated free 25(OH)DMeasured Free 25(OH)DCalculated bioavailable 25(OH)D 8.5 ± 3.1 nmol/L, 3.4 ± 1.24 μg/L
* no r providedr = −0.17*After supplementation:
Total 25(OH)D ~ 109 ± 26.2 nmol/L, 43.6 ± 10.48 ng/mL
Calculated free 25(OH)D 36.9 ± 9.4 pmol/l, 14.7 ± 3.7 ng/L
Measured free 25(OH)D 21.9 ± 5.2 pmol/L, 8.7 ± 2.08 ng/L
Yao et al, 2017 (45)448Age 30 years on averageBaseline bioavailable 25(OH)DSupplementation Total 25(OH)D and Bioavailable 25(OH)D*, r not providedBioavailable 25(OH) D and Calcium, r = 0.11*Total 25(OH) D by LC-MSVermeulen’s equationTotal 25(OH)D 32.8 nmol/L, 13.2 ± 3.52 ng/ mL
Intervention: 2000 IU/day for 20 weeksMale/ Female 141/307NSBioavailable 25(OH)D 2.7 ± 0.8 nmol/L, 1.08 ± 0.32 μg/L
Supplementation Bioavailable 25(OH)D*, no r providedAfter supplementation:
Total 25(OH)D 67.3 ± 23.1 nmol/L, 26.92 ± 9.24 ng/mL
Bioavailable 25(OH)D 3.0 ± 3 nmol/L, 1.2 ± 1.2 μg/L
Smith et al, 2019 (38)358Older women:Baseline free 25(OH) D, S, r = 0.73Total and measured free 25(OH)D*Total 25OHD by LC-MSTotal 25 (OH)D ~ 50.9 ± 13.2 nmol/L, 20.36 ± 5.28 ng/mL
Intervention: 400 to 4800 IU/day for 12 mosAge 66 years on averageSupplementation free 25(OH)D r = 0.86*Free 25(OH) D measured by ELISAFree 25 (OH)D ~ 9.21 ± 2.88 nmol/L, 3.68 ± 1.15 ng/L
Caucasian 140 (62%)
African American 88 (38%)
Younger women:
Age 37 years on average
Caucasian 91(70%)
African American 39 (30%)
Meryl LeBoff et al, 2020 (48)771Age 63 years on averagepQCT
percent change, NS
Total 25(OH) D by LC-MSTotal 25(OH)D 69.1 ± 22.7 nmol/L, 27.64 ± 9.08 ng/mL
Intervention: 2000 IU/ day for 2 yearsMale/ Female: 411/360Free 25(OH) D by ELISAFree 25(OH)D 14.6 ± 4.7 pmol/L, 5.9 ± 1.88 ng/L
White 630, Black 67, Hispanic 26, Asian 15After supplementation:
Native American or Alaskan native 5Total 25(OH)D 98.6 nmol/L, 39.44 ng/mL
Free 25(OH)D 22.3 pmol/L, 8.92 ng/L
Aspray et al, 2019 (47)379Age 74 years on averageTotal and measured free 25(OH)D, S, no rChange in BMD, NSTotal 25 (OH)D by LC-MSMathematical modelTotal 25(OH)D 41.6 ± 19.9 nmol/L, 16.64 ± 7.96 ngl/mL
Intervention: 12,000, 24,000, 48,000 IU/ mo for 12 mos,Male/ Female: 260/112Free 25(OH)D 8.7 ± 4.2 pmol/L, 3.48 ± 1.68 ng/L
Equivalent to 400 IU/ day, 800 IU/day, 1600 IU/day
After supplementation:
Total 25(OH)D [55.0-79] nmol/L, [22-31.6] ng/mL
Free 25(OH)D [11.7-16.8] pmol/L, [4.68-6.72] ng/L
Article InterventionNAge Gender RaceRelation to total 25(OH)DRelation to PTHRelation to calcium + BTM + BMDAssayFormula for calculated 25(OH)DRanges of vitamin D level
Sollid et al, 2016 (27)472Age 62 years on averageMeasured free 25(OH)DTotal 25(OH)DTotal 25(OH) D by LC-MSVermeulen’s equationTotal 25(OH)D ~ 63 ± 22 nmol/L, 25.2 ± 8.8 ng/mLCalculated free 25(OH) D 20 ± 7.4 pmol/L, 8 ± 2.96 ng/L
Intervention: 20,000 IU/weekMale/Female 293/179r = 0.73, Sr = −0.21*Free 25(OH) D by ELISAMeasured free 25(OH)D 13.4 ± 4.2 pmol/L, 5.36 ± 1.68 ng/L
OR 2857 IU/day for 12 mosCalculated free 25(OH)DMeasured Free 25(OH)DCalculated bioavailable 25(OH)D 8.5 ± 3.1 nmol/L, 3.4 ± 1.24 μg/L
* no r providedr = −0.17*After supplementation:
Total 25(OH)D ~ 109 ± 26.2 nmol/L, 43.6 ± 10.48 ng/mL
Calculated free 25(OH)D 36.9 ± 9.4 pmol/l, 14.7 ± 3.7 ng/L
Measured free 25(OH)D 21.9 ± 5.2 pmol/L, 8.7 ± 2.08 ng/L
Yao et al, 2017 (45)448Age 30 years on averageBaseline bioavailable 25(OH)DSupplementation Total 25(OH)D and Bioavailable 25(OH)D*, r not providedBioavailable 25(OH) D and Calcium, r = 0.11*Total 25(OH) D by LC-MSVermeulen’s equationTotal 25(OH)D 32.8 nmol/L, 13.2 ± 3.52 ng/ mL
Intervention: 2000 IU/day for 20 weeksMale/ Female 141/307NSBioavailable 25(OH)D 2.7 ± 0.8 nmol/L, 1.08 ± 0.32 μg/L
Supplementation Bioavailable 25(OH)D*, no r providedAfter supplementation:
Total 25(OH)D 67.3 ± 23.1 nmol/L, 26.92 ± 9.24 ng/mL
Bioavailable 25(OH)D 3.0 ± 3 nmol/L, 1.2 ± 1.2 μg/L
Smith et al, 2019 (38)358Older women:Baseline free 25(OH) D, S, r = 0.73Total and measured free 25(OH)D*Total 25OHD by LC-MSTotal 25 (OH)D ~ 50.9 ± 13.2 nmol/L, 20.36 ± 5.28 ng/mL
Intervention: 400 to 4800 IU/day for 12 mosAge 66 years on averageSupplementation free 25(OH)D r = 0.86*Free 25(OH) D measured by ELISAFree 25 (OH)D ~ 9.21 ± 2.88 nmol/L, 3.68 ± 1.15 ng/L
Caucasian 140 (62%)
African American 88 (38%)
Younger women:
Age 37 years on average
Caucasian 91(70%)
African American 39 (30%)
Meryl LeBoff et al, 2020 (48)771Age 63 years on averagepQCT
percent change, NS
Total 25(OH) D by LC-MSTotal 25(OH)D 69.1 ± 22.7 nmol/L, 27.64 ± 9.08 ng/mL
Intervention: 2000 IU/ day for 2 yearsMale/ Female: 411/360Free 25(OH) D by ELISAFree 25(OH)D 14.6 ± 4.7 pmol/L, 5.9 ± 1.88 ng/L
White 630, Black 67, Hispanic 26, Asian 15After supplementation:
Native American or Alaskan native 5Total 25(OH)D 98.6 nmol/L, 39.44 ng/mL
Free 25(OH)D 22.3 pmol/L, 8.92 ng/L
Aspray et al, 2019 (47)379Age 74 years on averageTotal and measured free 25(OH)D, S, no rChange in BMD, NSTotal 25 (OH)D by LC-MSMathematical modelTotal 25(OH)D 41.6 ± 19.9 nmol/L, 16.64 ± 7.96 ngl/mL
Intervention: 12,000, 24,000, 48,000 IU/ mo for 12 mos,Male/ Female: 260/112Free 25(OH)D 8.7 ± 4.2 pmol/L, 3.48 ± 1.68 ng/L
Equivalent to 400 IU/ day, 800 IU/day, 1600 IU/day
After supplementation:
Total 25(OH)D [55.0-79] nmol/L, [22-31.6] ng/mL
Free 25(OH)D [11.7-16.8] pmol/L, [4.68-6.72] ng/L

Values for 25(OH) D levels in italics provide values using units similar to ones in our study for ease of comparability, values of vitamin D metabolites correspond to values at baseline unless specified otherwise.

* indicates significance

Abbreviations: 25(OH)D, 25-hydroxyvitamin D; BMD, bone mineral density; BTM, bone turnover marker; LC-MS, liquid chromatography–mass spectrometry; NA, not available; NS, not significant; pQCT, peripheral quantitative computed tomography.

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