TABLE 3.
Effect of vitamin D intakes and ultraviolet exposures on circulating 25-hydroxyvitamin D concentrations1
| Group | Exposure source | Ratio of new to total RCTs2 | Quality of new RCTs3 |
| Adults (adapted from reference 13, Table 9, pp 108–110) | Fortified foods | 10:11 | 1 (1 RCT) |
| 2 (3 RCTs) | |||
| 3 (2 RCTs) | |||
| 4 (4 RCTs) | |||
| Infants (adapted from reference 13, Table 12, pp 135–136) | Supplement | 1:7 | 1 (1 RCT) |
| Pregnant or lactating women (adapted from reference 13, Table 12, pp 137–138) | Supplement | 1:6 | 2 (1 RCT) |
| Children and adolescents (adapted from reference 13, Table 12, p 139) | Supplement | 3:4 | 2 (1 RCT) |
| 3 (1 RCT) | |||
| 4 (1 RCT) | |||
| Premenopausal women and younger men (adapted from reference 13, Table 12, pp 140–142) | Supplement | 7:9 | 1 (2 RCTs) |
| 2 (3 RCTs) | |||
| 3 (2 RCTs) | |||
| Mixture of younger and older adults, community dwelling (adapted from reference 13, Table 12, pp 142–143) | Supplement | 3:4 | 1 (1 RCT) |
| 2 (2 RCTs) | |||
| Postmenopausal women and older men, community dwelling (adapted from reference 13, Table 12, pp 144–151) | Supplement | 21:31 | 1 (2 RCTs) |
| 2 (6 RCTs) | |||
| 3 (7 RCTs) | |||
| 4 (3 RCTs) | |||
| 5 (3 RCTs) | |||
| Postmenopausal women and older men, institutionalized (adapted from reference 13, Table 12, pp 151–154) | Supplement | 6:14 | 2 (3 RCTs) |
| 3 (3 RCTs) | |||
| Adults (adapted from reference 13, Table 11, pp 116–118) | Ultraviolet light | 1:8 | 2 (1 RCT) |
Data adapted from Cranney et al, 2007 (13). RCT, randomized clinical trial.
“New” refers to references not likely to have been available to the 1997 Dietary Reference Intake Committee and included all studies published after 1997 and studies published during 1997 that were not cited in the master reference list for the 1997 Institute of Medicine's report “Dietary Reference Intakes for Calcium, Phosphorus, Magnesium, Vitamin D, and Fluoride” (3) and excluded studies published before and during 1996 and studies published during 1997 that were cited in the master reference list for the 1997 Institute of Medicine's report.
The study quality was assessed in the systematic review (13) by using the validated Jadad scale with a score of ≥3 (out of a possible 5) indicating studies of higher quality.