Table 1.
Baseline Characteristics
| Characteristics | Total (n = 127) | Vitamin D (n = 66) | Placebo (n = 61) |
|---|---|---|---|
| Demographics | |||
| Age, y | 60.2 (8.4) | 60.1 (8.4) | 60.3 (8.5) |
| Female, n (%) | 38 (29.9) | 17 (25.8) | 21 (34.4) |
| Race, n (%)a | |||
| White | 79 (62.2) | 41 (62.1) | 38 (62.3) |
| Black or African-American | 38 (29.9) | 17 (25.8) | 21 (34.4) |
| Asian | 6 (4.7) | 4 (6.1) | 2 (3.3) |
| Other | 4 (3.1) | 4 (6.1) | 0 (0) |
| Hispanic or Latino ethnicity, n (%)a | 3 (2.4) | 2 (3.0) | 1 (1.6) |
| Season at study entry, n (%) | |||
| January–March | 33 (26.0) | 15 (22.7) | 18 (29.5) |
| April–June | 45 (35.4) | 27 (40.9) | 18 (29.5) |
| July–September | 32 (25.2) | 17 (25.8) | 15 (24.6) |
| October–December | 17 (13.4) | 7 (10.6) | 10 (16.4) |
| Self-reported vitamin D intake, units/db | 399 (343) | 407 (381) | 391 (301) |
| Self-reported calcium intake, mg/db | 931 (513) | 1006 (597) | 852 (394) |
| Smoking status, n (%) | |||
| Never smoked | 48 (37.8) | 22 (33.3) | 26 (42.6) |
| Currently smoking | 14 (11.0) | 8 (12.1) | 6 (9.8) |
| Formerly smoked | 64 (50.4) | 35 (53.0) | 29 (47.5) |
| Prefer not to answer | 1 (0.8) | 1 (1.5) | 0 (0) |
| Clinical characteristics | |||
| Weight, kg | 92.0 (15.5) | 91.2 (15.9) | 92.9 (15.1) |
| BMI, kg/m2 | 30.9 (3.8) | 30.7 (3.9) | 31.2 (3.8) |
| Metformin use, n (%) | 99 (78.0) | 51 (77.3) | 48 (78.7) |
| Laboratory | |||
| Serum calcium, mg/dL | 9.5 (0.4) | 9.5 (0.4) | 9.4 (0.3) |
| Vitamin D status | |||
| Plasma 25(OH)D, ng/mL | 26.6 (11.1) | 25.8 (10.3) | 27.5 (12.0) |
| Plasma 25(OH)D <20 ng/mL, n (%) | 33 (26.0) | 19 (28.8) | 14 (23.0) |
| Plasma 25(OH)D <30 ng/mL, n (%) | 80 (63.0) | 42 (63.6) | 38 (62.3) |
| HbA1c, % | 6.6 (0.5) | 6.6 (0.6) | 6.5 (0.5) |
Values are means (standard deviation) unless otherwise specified. Percentages may not total 100 because of rounding. To convert 25(OH)D from ng/mL to mmol/L, multiply by 2.456; to convert vitamin D intake from international units to μg, divide by 40.
a
Race and ethnicities were self-reported and followed National Institutes of Health guidelines. Participants could check multiple categories. Asian includes “Chinese” (n = 3) and “Other Asian” (n = 3). Other includes “Native Hawaiian or Other Pacific Islander” (n = 1) and “Other” (n = 3).
b
Data are derived from the food frequency questionnaire.