Table 4.
Ongoing and completed randomized, placebo-controlled trials of vitamin D supplementation and diabetes risk
| D2d | Tromsø study | DPVD | VITAL | D-Health | DO-HEALTH | |
|---|---|---|---|---|---|---|
| N | 2,423 | 511 | 750 (target) | 25,874 | 21,315 | 2,157 |
| Years conducted (country) | 2013–2018 (estimated) (U.S.) | 2008–2015 (Norway) | 2013–unknown (estimated) (Japan) | 2010–2018 (estimated) (U.S.) | 2014–2025 (estimated) (Australia) | 2012–2017 (estimated) (Europe) |
| Diabetes outcome | Primary | Primary | Primary | Secondary1 | Secondary2 | Secondary (fasting glucose, insulin)3 |
| Glycemic inclusion criteria | At least two of three ADA criteria for prediabetes: 2hPG 140–199 mg/dL, FPG 100–125 mg/dL, HbA1c 5.7–6.4% | 2hPG 140–198 mg/dL and/or FPG 108–124 mg/dL4 | 2hPG 140–199 mg/dL and fasting glucose <126 mg/dL and HbA1c <6.5% | None | None | None |
| Active intervention | Two arms: 4,000 IU vitamin D3 daily vs. placebo | Two arms: 20,000 IU vitamin D3 weekly (∼2,900 daily) vs. placebo | Two arms: 0.75 μg eldecalcitol (1,25[OH]2D3) daily vs. placebo | 2 × 2 factorial design: 2,000 IU D3 daily, 1 g daily marine n-3 fatty acid vs. placebos | Two arms: 60,000 IU D3 monthly vs. placebo | 2 × 2 × 2 factorial design: 2,000 IU D3 daily, 1 g marine n-3 fatty acid daily, exercise program |
| Personal use of vitamin D from supplements, % of participants (maximum amount allowed) | 43 (1,000 IU/day) | 35 (<400 IU/day) | Not available | Not available (800 IU/day) | Not available (500 IU/day [2,000 IU/day if prescribed]) | Not available (800 IU/day) |
| Treatment duration, years | ∼3 (estimated) | 5 | 2.8 | 5 | 5 | 3 |
DO-HEALTH, Vitamin D3 – Omega3 – Home Exercise – HeALTHy Ageing and Longevity Trial; VITAL, VITamin D and OmegA-3.
1Primary outcomes: cancer, major adverse cardiovascular events.
2Primary outcome: all-cause mortality.
3Primary outcomes: nonvertebral fracture, functional decline, blood pressure, cognitive decline, infection.
4HbA1c added as inclusion requirement midway through recruitment; all participants had HbA1c between 5.8 and 6.9%.