Table 1.
Serum 25(OH)D, dietary vitamin D intake, and UVB exposure by season and population
| Measure | Summer | Winter | P value* |
| Serum 25(OH)D, median nmol/L (range): Xhosa | 72.6 (62.1–80.43)† | 45.4 (35.7–51.2) | <0.0001 |
| Serum 25(OH)D, median nmol/L (range): Cape Mixed | 65.5 (54.6–76.1) | 43.8 (33.5–54.2) | <0.0001 |
| Vitamin D status, nmol/L (%) | <0.0001 | ||
| Xhosa: Severe deficiency, <30 nmol/L | 0 | 6 (18) | |
| Xhosa: Deficiency, <50 nmol/L | 2 (4) | 21 (64) | |
| Xhosa: Insufficiency, 50–75 nmol/L | 28 (56) | 11 (33) | |
| Xhosa: Sufficiency, >75 nmol/L | 20 (40) | 1 (3) | |
| Cape Mixed: Severe deficiency, <30 nmol/L | 0 | 6 (12) | |
| Cape Mixed: Deficiency, <50 nmol/L | 8 (16) | 35 (70) | |
| Cape Mixed: Insufficiency, 50–75 nmol/L | 27 (54) | 15 (30) | |
| Cape Mixed: Sufficiency, >75 nmol/L | 15 (30) | 0 | |
| Dietary vitamin D intake, median IU/d (IQR): Xhosa | 213 (94–335) | 170 (68–266) | 0.26 |
| Dietary vitamin D intake, median IU/d (IQR): Cape Mixed | 235 (120–395) | 230 (99–369) | 0.24 |
| Personal weekly UVB, median J (IQR): Xhosa | 42,982 (28,651–90,552)† | 1,304 (875.5–2,878) | <0.0001 |
| Personal weekly UVB, median J (IQR): Cape Mixed | 20,603 (10,887–42,897) | 1,450 (392.6–3,530) | <0.0001 |
*
Wilcoxon rank test or Fisher's exact test between seasons, bold type indicates statistically significant difference between summer and winter values.
†
Mann–Whitney test significant between populations, P < 0.04, bold type indicates statistically significant difference between summer and winter values.