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The effect of vitamin D3 supplementation on fracture incidence in an aging population - The Finnish vitamin D trial

Rikkonen T, Hantunen S, Kröger H, Lamberg-Allardt C, Manson JE, Nurmi T, Tuppurainen M, Voutilainen A et al.

Bone, 2026

2,495 participants

Abstract

Background: The effectiveness of vitamin D supplementation for fracture prevention at the population level remains a matter of debate. In this study, we evaluated the impact of vitamin D₃ supplementation on fracture risk among an aging population in Finland.

Methods: The study included 2495 participants, men ≥60 years and women ≥65 years, who were randomized for 5 years into three groups: 1600 IU/day or 3200 IU/day of vitamin D₃, or placebo. Fracture diagnoses were retrieved from two national care notification registers.

Results: During the mean 4.1-year supplementation period, there were 49, 73 and 52 fractures in the placebo, 1600 IU/day (compared to placebo: HR = 1.52, 95% CI = 1.06-2.18) and 3200 IU/day (HR = 1.07, 95% CI = 0.72-1.58) arms, respectively. During the extended 7.3-year follow-up, 104, 139 and 111 fractures occurred in the placebo, 1600 IU/day (HR = 1.40, 95% CI = 1.08-1.80) and 3200 IU/day (HR = 1.08, 95% CI = 0.83-1.41) arms, respectively. No statistically significant differences were observed in fracture subtypes. Age, sex, BMI, history of fracture or fall, osteoporosis diagnosis, or calcium supplement use did not modify the effects. In the sub-cohort of 550 participants, the mean ± SD baseline serum 25-hydroxyvitamin D concentration was 74.8 ± 18.2 nmol/L. After 12 months, the concentrations were 73.0 ± 17.8, 99.7 ± 21.1 and 120.4 ± 21.8 nmol/L in the placebo, 1600 IU/day and 3200 IU/day arms, respectively (P < 0.001).

Conclusions: The 5-year vitamin D3…

How strong is the evidence?

Evidence Hub reads this as a randomized trial, done in people. Its evidence level is 2 of 5 (High · randomized trial). Randomized trials of a reasonable size are the strongest single-study design. Reported size: 2,495 participants or records.

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