Serum concentrations of 1,25-dihydroxyvitamin D2 and 1,25-dihydroxyvitamin D3 in response to vitamin D2 and vitamin D3 supplementation

Abstract

Objective: The purpose of this study was to determine 1,25-dihydroxyvitamin D3 [1,25(OH)2D3] and 1,25-dihydroxyvitamin D2 [1,25(OH)2D2] levels in healthy adults consuming 1000 IU vitamin D2 or vitamin D3 per day for 11 weeks.

Subjects and design: Blood from 34 healthy male and female adults, aged 18 to 79 years, from a placebo-controlled, double-blind study who received a placebo, 1000 IU vitamin D3, or 1000 IU vitamin D2 daily for 11 weeks at end of winter was analyzed. Serum levels of 25-hydroxyvitamin D2, 25-hydroxyvitamin D3, 1,25(OH)2D2, and 1,25(OH)2D3 were determined by liquid chromatography-tandem mass spectroscopy.

Results: Of the adults, 82% were vitamin D insufficient (serum 25-hydroxyvitamin D [25(OH)D <30 ng/mL]) at the start of the study. Administration of vitamin D2 and vitamin D3 induced similar increases in total 25(OH)D as well as in 25-hydroxyvitamin D2 and 25-hydroxyvitamin D3, respectively. Compared with placebo and adjusting for baseline levels, 1000 IU daily of vitamin D2 was associated with a mean increase of 7.4 pg/mL (95% confidence interval, 4.4-10.3) in 1,25(OH)2D2, which was accompanied by a mean decrease of 9.9 pg/mL (-15.8 to -4.0) in 1,25(OH)2D3. No such differences accompanied administration of 1000 IU daily of vitamin D3.

Conclusion: Vitamin D2 and vitamin D3 were effective in raising and maintaining total serum concentrations of 25(OH)D. Ingestion of vitamin D2 also resulted in an increase in serum concentrations of 1,25(OH)2D2. This increase was accompanied by a comparable decrease in serum concentrations of 1,25(OH)2D3; therefore, the total 1,25-dihydroxyvitamin D [1,25(OH)2D] concentrations did not significantly change after 11 weeks compared with baseline levels. Ingestion of vitamin D3 did not alter serum concentrations of 1,25(OH)2D3 or total 1,25(OH)2D. Therefore, ingestion of 1000 IU vitamin D2 or vitamin D3 for 11 weeks was effective in raising total serum concentrations of 25(OH)D as well as sustaining serum concentrations of total 1,25(OH)2D.

Figure 1.

A, Total 25(OH)D levels are demonstrated over time. Shown are mean (± SEM) serum total 25(OH)D (♦; n = 9), serum 25(OH)D₃ (■; n = 9), and serum 25(OH)D₂ (▴; n = 9) after oral administration of either 1000 IU vitamin D₃ in orange juice or vitamin D₃ in capsules. There were no statistically significant differences in serum 25(OH)D₂ over time in the groups receiving either 1000 IU vitamin D₃ in orange juice or vitamin D₃ in capsules (2-tailed paired t test, P > .05). *P < .05 comparing serum total 25(OH)D and 25(OH)D₃ over time in the groups receiving either 1000 IU vitamin D₃ in orange juice or vitamin D₃ in capsules. B, Total 25(OH)D levels are demonstrated over time. Shown are mean (± SEM) serum total 25(OH)D (♦; n = 17), serum 25(OH)D₃ (■; n = 17), and serum 25(OH)D₂ (▴; n = 17) after oral administration of either 1000 IU vitamin D₂ in orange juice or vitamin D₂ in capsules. There were no statistically significant differences in serum total 25(OH)D and 25(OH)D₃ over time in the groups receiving either 1000 IU vitamin D₂ in orange juice or vitamin D₂ in capsule (2-tailed paired t test, P > .05). **P = .0005 comparing serum 25(OH)D₂ over time in the groups receiving either 1000 IU vitamin D₂ in orange juice or vitamin D₂ in capsules. C, Total 25(OH)D levels are demonstrated over time. Shown are mean (± SEM) serum total 25(OH)D (♦; n = 8), serum 25(OH)D₃ (■; n = 8), and serum 25(OH)D₂ (▴; n = 8) after oral administration of either unfortified orange juice or placebo capsule. There were no statistically significant differences in serum total 25(OH)D, 25(OH)D₃, and 25(OH)D₂ over time in the groups receiving either unfortified orange juice or placebo capsule (2-tailed paired t test, P > .05).

Figure 2.

A, Total 1,25(OH)₂D levels are demonstrated over time. Shown are mean (± SEM) serum total 1,25(OH)₂D (♦; n = 9), serum 1,25(OH)₂D₃ (■; n = 9), and serum 1,25(OH)₂D₂ (▴; n = 9) after oral administration of either 1000 IU vitamin D₃ in orange juice or vitamin D₃ in capsules. There were no statistically significant differences in serum 1,25(OH)₂D, 1,25(OH)₂D₃, or 1,25(OH)₂D₂ over time in the groups receiving either 1000 IU vitamin D₃ in orange juice or vitamin D₃ in capsules (2-tailed paired t test, P > .05). B, Total 1,25(OH)₂D levels are demonstrated over time. Shown are mean (± SEM) serum total 1,25(OH)₂D (♦; n = 17), serum 1,25(OH)₂D₃ (■; n = 17), and serum 1,25(OH)₂D₂ (▴; n = 17) after oral administration of either 1000 IU vitamin D₂ in orange juice or vitamin D₂ in capsules. There were no statistically significant differences in serum total 1,25(OH)₂D and 1,25(OH)₂D₃ over time in the groups receiving either 1000 IU vitamin D₂ in orange juice or vitamin D₂ in capsules (2-tailed paired t test, P > .05). *P < .05 comparing serum 1,25(OH)₂D₂ over time in the groups receiving 1000 IU vitamin D₂ in orange juice or in capsules. C, Total 1,25(OH)₂D levels demonstrated over time. Shown are mean (± SEM) serum total 1,25(OH)₂D (♦; n = 8), serum 1,25(OH)₂D₃ (■; n = 8), and serum 1,25(OH)₂D₂ (▴; n = 8) after oral administration of either unfortified orange juice or placebo capsule. There were no statistically significant differences in serum total 1,25(OH)₂D, 1,25(OH)₂D₃, and 1,25(OH)₂D₂ over time in the groups receiving either unfortified orange juice or placebo capsule (2-tailed paired t test, P > .05).