Table 1.
Characteristics of included studies.
| References | Participants | Intervention | Outcome | ||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
| No. of randomized participants (No. of female) | Age, years, mean (SD) | Latitude | Menopausal status | Baseline serum 25(OH)D level | Baseline MD | Type of vitamin D, dose | Control group | Administration | Follow-up duration | Outcome measures | |
| Incidence | |||||||||||
| Avenell et al. (55) | 5,292 (4,481) | 77 (6) | 50–59°N (across UK) | Post | Vit D group had 32% participants at high risk of Vit D deficiency; placebo group had 31.6% | N/A | D3, 800 IU/day | Placebo, p + ca | Oral | 4 months | N/A |
| Lappe et al. (57) | 1,180 (1,180) | 66.7 (7.3) | 41.4°N | Post | Vit D + Ca group: 71.8 (20.0) nmol/L; Ca group: 71.6 (20.5) nmol/L | N/A | D3, vitamin D 1,100 IU/day and Ca 1,400–1,500 mg/day | Ca 1,400–1,500 mg/day | Oral | 4 years | N/A |
| Larsen et al. (53) | 112 (77) | 61 (10) | 56°N | Post | Vit D group: 23(9) ng/ml; placebo group: 23 (12) ng/ml | N/A | D3, 3,000 IU/day | Placebo | Oral | 20 weeks | N/A |
| Manson et al. (58) | 25,871 (13,085) | 67.1 (7.1) | N/A | N/A | 30.8 (10.0) ng/ml (77 nmol/L) | N/A | D3, vitamin D 2,000 IU/day or vitamin D 2,000 IU/day and n-3 fatty acid 1g/day | Placebo or placebo and n-3 fatty acid 1 g/day | Oral | Median follow-up of 5.3 years (range, 3.8–6.1) | Through the national health service databases |
| Murdoch et al. (54) | 322 (241) | 47 | 43°31′48″S | N/A | Vit D group: 9 (9) ng/ml; placebo group: 28 (9) ng/ml | N/A | D3, 200,000 IU for 1 month then 100,000 IU/month | Placebo | Oral | 18 months | The medical record was examined |
| Witham et al. (52) | 159 (77) | 76.8 | 55.86 N | Post | Vit D group: 18 (6) ng/ml; placebo group: 18 (6) ng/ml | N/A | D3, 100,000 U/3 months | Placebo | Oral | 12 months | Cancer was confirmed on the basis of histologic or cytologic data.14 |
| Wood et al. (56) | 305 (305) | Vit D group: 63.5 (1.9); 62.1 (2.3); placebo group: 63.9 (2.3) | 57.15°N | Post | Vit D group: 32.74 (12.9), 32.41 (13.8) ng/ml; placebo group: 36.18 (17.1) ng/ml | N/A | D3, 400 IU/day, 1,000 IU/day | Placebo | Oral | 12 months | N/A |
| Mammography density | |||||||||||
| Brisson et al. (25) | 405(405) | 42.7 | 46°48′N | Pre | Vit D group: 65.1 (24.7), 65.6 (25.4), 59.3 (21.0) nmol/L; placebo group: 65.7 (23.5) nmol/L | Vit D groups: 38.3 (14.5), 37.2 (15.2), 37.9 (15.8); placebo group: 40.8 (17.2) | D3, 1,000 IU/day, 2,000 IU/day, 3,000 IU/day | Placebo | Oral | 12 months | Breast Imaging Reporting and Data System (BIRADS), semi-automated and automated methods |
| Crew et al. (39) | 204(204) | 44.6 | N/A | Pre | Vit D group: 23.9 (7.2) ng/ml, placebo group: 23.7 (8.4) ng/ml | Vit D group: 38.6 (18.0); placebo group: 35.0 (19.0) | D3, 20,000 IU/week | Placebo | Oral | 24 months | Semi-automated methods with the Cumulus software |
| Wood et al. (38) | 300(300) | 42.6 (6.4) | N/A | Pre | 26.6 (11.7) ng/ml | 49% of women had MD between 25 and 50% with only 12% over 50% dense | D3, 2,000 IU/day | Placebo | Oral | 12 months | Digital computed radiography (CR) and digital direct radiography (DR) |
SD, standard deviation; MD, mammography density; RR, risk ratio.