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High-dose monthly vitamin D fails to prevent falls, fractures
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In a diverse population of healthy adults living in New Zealand, a large monthly dose of cholecalciferol taken for a mean of 3 years did not affect the risk for falls or nonvertebral fractures when compared with placebo, according to findings from a randomized controlled trial.
“The association between vitamin D deficiency and rickets and osteomalacia is well established, and the general consensus is that concentrations below 25 nmol/L are associated with greatly increased risk of these conditions,” Kay-Tee Khaw, MB BChir, professor in the department of public health and primary care at the University of Cambridge, United Kingdom, and colleagues wrote. “However, the optimum vitamin D status for other health outcomes is subject to debate in terms of the optimum concentration in blood of 25-[hydroxyvitamin] D above deficiency levels and the oral vitamin D dose needed to maintain particular blood concentrations of 25-(OH)D when sunlight exposure is inadequate.”
Khaw and colleagues analyzed data from 5,110 healthy adults aged 50 to 84 years who were not taking vitamin D supplements as part of the Vitamin D Assessment (ViDA) study, a randomized controlled trial to assess whether monthly oral cholecalciferol would reduce the risk for cardiovascular disease, respiratory illness or fractures (mean age, 66 years; 58% men; mean baseline 25-(OH)D level, 63 nmol/L). Participants were recruited between April 2011 and November 2012 from the Auckland, New Zealand, area. Researchers assigned participants to an initial oral dose of 200,000 IU cholecalciferol (vitamin D3), followed by 100,000 IU cholecalciferol monthly (n = 2,558) or placebo (n = 2,552). All participants completed baseline interviews regarding medical and fall history. Falls were self-reported via questionnaire; fractures were identified via hospital discharge records and records from the Accident Compensation Corporation system, a national government insurance organization covering all New Zealand residents. Secondary outcomes were fracture data and post hoc outcome data for falls; researchers used Cox proportional hazard methods to estimate HRs for time to first fracture or time to first fall. Within the cohort, 30% had a 25-(OH)D concentration of 50 nmol/L or less.
During a mean follow-up of 3.4 years, 2,638 participants reported having a fall — 1,312 (52%) of adults in the vitamin D group vs. 1,326 (53%) of adults in the placebo group. Nonvertebral fractures were reported for 292 participants — 6% adults in the vitamin D group vs. 5% of adults in the placebo group.
After adjustment for age, sex, race, fall history, physical activity and baseline 25-(OH)D level, HR for falls was 0.99 (95% CI, 0.92-1.07) for those in the vitamin D group vs. placebo; adjusted HR for fracture was 1.19 (95% CI, 0.94-1.5) for the vitamin D group vs. placebo.
During the trial, 123 participants died (65 in vitamin D group vs. 58 in placebo group).
The researchers noted that the community-based trial included men, had a wide age range and different ethnic groups who have been documented to have a high prevalence of vitamin D deficiency.
“Although the aim of the ViDA trial was to increase concentrations to 80-100 nmol/L, the mean amounts recorded in participants allocated vitamin D supplementation were substantially higher, around 120 nmol/L on average, and more than twice that noted in individuals allocated placebo,” the researchers wrote. “Nevertheless, although U-shaped associations between amounts of 25-(OH)D and fractures and falls could account for the overall lack of effect on risk of falls and fractures (if supplementation resulted in some individuals having very high concentrations that might increase risk), we noted no differences in falls and fractures associated with supplementation in individuals stratified by baseline 25-(OH)D status. Thus, even people with low amounts seemed to derive no fracture risk reduction from supplementation.”
The researchers added that, although the study had low power for fracture endpoints, the findings suggest that large monthly bolus doses of vitamin D do not confer an overall benefit. – by Regina Schaffer
Disclosure: The researchers report no relevant financial disclosures.
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