Table 2.
Characteristics of the 5 studies included in the meta-analysis of vitamin D supplementation and cancer mortality from Keum et al. [1], sorted by daily dose.
| First Author, Year (Reference) | Country | Participants | %Women | Mean Age (Age Range) (Years) | Duration of Intervention (Years) | Follow-Up (Years) | Supplementation Dose | Baseline 25(OH)D (nmol/L) | Increase in 25(OH)D Levels, Measurement | RR (95% CI) for Cancer Mortality |
|---|---|---|---|---|---|---|---|---|---|---|
| Wactawski-Wende 2006 [11] | USA | N = 36,282; post-menopausal women | 100 | 50–79 | Mean 7 | Mean 7 | 400 IU/day | Median (IQR) 42.4 (31.0–58.3) | Intervention: +12 nmol/L Control: NR |
0.89 (0.77–1.03) |
| Avenell 2012 [13] | UK | N = 5292; previous low-trauma fracture | 84.7 | 77 (≥70) | 2–5 | 3 | 800 IU/day | Mean 38 | Intervention: +24 nmol/L after 1 year Control: +6 nmol/l after 1 year |
0.85 (0.68–1.06) |
| Trivedi 2003 [9] | UK | N = 2686; doctors | 31.9 | 74.8 (65–85) | 5 | 5 | 100,000 IU/ 4 months (≙820 IU/day) | Not measured | Vs. placebo Men: +14.6 nmol/L Women: +26.4 nmol/L,~3 weeks after intake (Sept/Oct) |
0.86 (0.61–1.20) |
| Manson 2018 [10] | USA 1 | N = 25,871; 71% white, 20.2% black, 4% Hispanic | 50.6 | 67.1 (men ≥ 50, women ≥ 55) | 3–6 | Median (range) 5.3 (3.8–6.1) | 2000 IU/day | Median 71 | Intervention: +30 nmol/L Placebo: −2 nmol/L, 1 year after first dose |
0.83 (0.67–1.02) |
| Scragg 2018 [12] | New Zealand | N = 5110; residents of Auckland | 41.9 | 65.9 (50–84) | Median (range) 3.3 (2.5–4.2) | Median 3.3 | 200,000 IU initial bolus + 100,000 IU/month | Mean (SD) 66.3 (22.5) | Intervention: +56–+71 nmol/L Control: +7–+22 nmol/L |
0.99 (0.60–1.64) |
Abbreviations: 25(OH)D, 25-hydroxyvitamin D; RR, relative risk; CI, confidence interval; IU, international units; IQR, inter-quartile range; L, liter; SD, standard deviation; NR, not reported. 1 Note: The mortality reduction of 17% with 2000 IU/day in the study of Manson et al. was observed even though fortification of foods with vitamin D is already allowed in the USA to a large extent since 18 July 2016 (up to 84 IU/100 g of vitamin D3 to milk, 84 IU/100 g of vitamin D2 to plant-based beverages intended as milk alternatives, and 89 IU/100 g of vitamin D2 to plant-based yogurt alternatives) [20].