Table 2

Effects of vitamin D supplementation on insulin sensitivity, insulin secretion, and glucose metabolism

Vitamin DPlacebo
BaselineΔ Study endWithin-groupP valueBaselineΔ Study endWithin-groupP valueBetween-group P value
Fasting plasma glucose (mmol/L)11.3 ± 3.50.6 ± 2.60.3210.0 ± 3.10.6 ± 2.80.26
HbA1c (%)7.9 ± 1.4−0.3 ± 0.90.117.5 ± 1.3−0.2 ± 0.50.0520.98
Fasting insulin (mmol/L)105 ± 1431 ± 80.91123 ± 9921 ± 900.250.38
Fasting C-peptide (pmol/L)1,026 ± 4308 ± 2640.871,162 ± 37344 ± 2420.370.73
AIRg 0–8161 ± 22611 ± 280.70294 ± 282−37 ± 2760.510.10
ΔC-peptide max484 ± 433−91 ± 3780.20592 ± 3512 ± 2150.970.04
Glucose infusion rate (μmol/kg FFM/min)30.1 ± 17.0−0.6 ± 14.30.8325.0 ± 14.4−0.5 ± 10.30.830.68
Total Rd (μmol/kg FFM/min)43.8 ± 20.31.9 ± 25.00.6933.9 ± 15.42.3 ± 15.20.470.52
Basal EGP (μmol/kg FFM/min)18.3 ± 6.61.6 ± 10.30.4215.9 ± 6.21.7 ± 5.50.170.37
Clamp EGP (μmol/kg FFM/min)12.9 ± 9.54.4 ± 17.40.199.5 ± 5.63.8 ± 6.80.0120.17
Basal glucose oxidation (μmol/kg FFM/min)7.1 ± 4.70.6 ± 4.60.507.1 ± 4.20.3 ± 7.10.840.88
Basal nonoxidative glucose consumption (μmol/kg FFM/min)9.7 ± 8.01.9 ± 7.60.249.1 ± 6.91.8 ± 7.70.310.66
Basal fat oxidation (mg/kg FFM/min)1.25 ± 0.39−0.09 ± 0.400.271.19 ± 0.350.01 ± 0.640.940.61
Clamp glucose oxidation (μmol/kg FFM/min)13.0 ± 5.70.6 ± 6.50.6311.8 ± 6.1−0.3 ± 7.50.850.47
Clamp nonoxidative glucose consumption (μmol/kg FFM/min)29.3 ± 21.83.2 ± 25.10.5222.8 ± 16.45.3 ± 15.10.150.87
Clamp fat oxidation (mg/kg FFM/min)0.92 ± 0.42−0.15 ± 0.390.080.74 ± 0.460.11 ± 0.560.410.20
Resting energy expenditure (kcal/day)1,677 ± 319−60 ± 1330.0341,720 ± 325−17 ± 2460.750.31
Clamp energy expenditure (kcal/day)1,759 ± 351−59 ± 1820.121,756 ± 333−100 ± 2320.070.82
  • Data are mean ± SD. AIRg, acute insulin response to glucose; FFM, free fat mass.