Table 1

Baseline characteristics of participants in categories defined by intratrial mean serum 25(OH)D level

Intratrial mean serum 25(OH)D category
Characteristic<50 nmol/L (n = 247)50–74 nmol/L (n = 456)75–99 nmol/L (n = 590)100–124 nmol/L (n = 413)≥125 nmol/L (n = 452)
Assigned to vitamin D at randomization, n (%)22 (8.9)78 (17.1)225 (38.1)319 (77.2)430 (95.1)
Serum 25(OH)D (nmol/L), median (IQR)40 (32.5–47.5)62.5 (50–70)77.5 (62.5–87.5)75 (57.5–92.5)86.3 (70–102.5)
 Among those assigned to vitamin D37.5 (30–40)43.8 (35–52.5)57.5 (45–70)67.5 (52.5–80)85 (67.5–102.5)
 Among those assigned to placebo40 (32.5–47.5)65 (55–72.5)85 (77.5–92.5)105 (97.5–117.5)122.5 (112.5–150)
Age (years)55.3 ± 10.559.2 ± 10.161.4 ± 9.560.9 ± 9.562.8 ± 8.3
Women, n (%)94 (38.1)206 (45.2)254 (43.1)173 (41.9)240 (53.1)
Race, n (%)*
 White100 (40.5)302 (66.2)424 (71.9)299 (72.4)330 (73.0)
 Black125 (50.6)121 (26.5)111 (18.8)86 (20.8)87 (19.2)
 Asian16 (6.5)21 (4.6)35 (5.9)23 (5.6)22 (4.9)
 Other6 (2.4)12 (2.6)20 (3.4)5 (1.2)13 (2.9)
Dietary supplement use
 Vitamin D
  Participants taking vitamin D supplements, n (%)37 (15.0)159 (34.9)306 (51.9)205 (49.6)237 (52.4)
  Vitamin D intake among all participants (μg/day)2.5 ± 6.66.1 ± 9.19.3 ± 10.29.2 ± 10.110.1 ± 10.6
  Vitamin D intake among participants using supplements, μg/day16.9 ± 7.217.5 ± 6.318.0 ± 6.618.6 ± 6.019.2 ± 6.2
 Calcium
  Participants taking calcium supplements, n (%)28 (11.3)135 (29.6)241 (40.8)162 (39.2)175 (38.7)
  Calcium intake among all participants (mg/day)33 ± 11293 ± 171125 ± 180126 ± 188125 ± 191
  Calcium intake among participants using supplements (mg/day)290 ± 192314 ± 173307 ± 152320 ± 168322 ± 175
BMI (kg/m2)33.5 ± 4.832.4 ± 4.332.0 ± 4.532.0 ± 4.430.7 ± 4.2
Physical activity (total MET h/week), median (IQR)41.9 (17.7–101.1)52.1 (25.4–124.3)57.3 (27.1–123.9)59.5 (25.9–120)64 (27.9–136.2)
Smoking, n (%)
 Never150 (60.7)282 (61.8)337 (57.1)243 (58.8)247 (54.7)
 Former72 (29.2)138 (30.3)214 (36.3)143 (34.6)187 (41.4)
 Current23 (9.3)34 (7.5)30 (5.1)25 (6.1)15 (3.3)
 Unknown or not reported2 (0.8)2 (0.4)9 (1.5)2 (0.5)3 (0.7)
HbA1c
 %5.9 ± 0.25.9 ± 0.25.9 ± 0.25.9 ± 0.25.9 ± 0.2
 mmol/mol41 ± 2.241 ± 2.241 ± 2.241 ± 2.241 ± 2.2
Statin use, n (%)71 (28.7)173 (37.9)270 (45.8)209 (50.6)211 (46.7)
  • Data are mean ± SD unless otherwise indicated. Percentages may not total 100 because of rounding. To convert the values for 25(OH)D to ng/L, divide by 2.496. To convert vitamin D intake to units, multiply by 40. IQR, interquartile range.

  • * Race was reported by the participant. The category “other” includes Asian, American Indian or Alaska Native, Native Hawaiian or other Pacific Islander, or other race.

  • Data on vitamin D and calcium intake are derived from a question about dietary supplements, including multivitamins and high-dose prescribed doses. Participants were allowed to take supplements up to 25 μg (1,000 units) per day of vitamin D and 600 mg per day of calcium. Dietary intake of vitamin D and calcium was not limited.

  • Value shown is among all participants regardless of whether they reported use of supplements.