Table 5

Estimates of the change in serum 25(OH)D concentration over time and by cumulative vitamin D3 dose
Model parameters (units) [25(OH)D] over time (days) in Vitamin D group1 [25(OH)D] over time (days) among all participants2 [25(OH]D] by dose (mcg) among all participants2
β 95% CI [LB, UB] β 95% CI [LB, UB] β 95% CI [LB, UB]
Reference Day 0 (baseline) Placebo group at Day 0 (baseline) 0 mcg of Vitamin D
25(OH)D at ref. point (nmol/L) 45.5 [41.0, 49.9] 44.4 [39.7, 49.1] 42.1 [39.1, 45.1]
Difference in 25(OH)D between groups at day 0 (nmol/L) 1.1 [−5.3, 7.6]
Decay rate (days-1 or mcg-1) 0.04 [0.03, 0.05] 0.04 [0.03, 0.05] 0.0003 [0.0002, 0.0004]
Δ25(OH)D at steady-state in placebo group (nmol/L) −7.1 [−12.3, -1.9]
Effect of vitamin D on Δ25(OH)D at steady-state (nmol/L) 94.4 [83.9, 104.9] 101.6 [89.7, 113.4]3 98.3 [88.7, 107.9]
Attained steady-state 25(OH)D (nmol/L) 139.9 [130.1, 149.6] 138.8 [127.4, 150.2] 140.4 [131.2, 149.6]
Adjusted R2 0.72 0.75 0.75
AIC 3907.2 3904.4

180 participants in the vitamin D group, contributing 220 specimens. Negative exponential model (vitamin D group): [25(OH)D]t = [25(OH)D]t = 0 + a1(1 − e− kt); where t is time, a is the Δ25(OH)D (where Δ is the change from baseline) at steady-state in the placebo group, and k is the decay rate to the asymptote.

2 The models include 160 participants overall (n = 80 in each group) contributing 433 specimens. Negative exponential model (both groups):

[25(OH)D]t = [25(OH)D]t = 0 + β g + (gd + a0)(1 − e− kt); where t is time, a is the Δ25(OH)D at steady-state in the placebo group, k is the decay rate to asymptote, g is group assignment and d is the difference in Δ25(OH)D between groups at steady-state,

3 Difference in Δ25(OH)D between placebo and vitamin D groups at modeled steady-state.

Roth et al.

Roth et al. Nutrition Journal 2013 12:47   doi:10.1186/1475-2891-12-47

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