1University of Auckland
Calcium and vitamin D were recommended for management of fracture risk for 30 years, on the basis of plausibility, studies with surrogate outcomes and a clinical trial conducted in a frail institutionalized vitamin D-deficient population. By 2015, 44 observational studies had reported that 70-90% of associations between calcium intake and fracture incidence were neutral. Among 26 randomized trials (69,107 participants) of calcium or calcium with vitamin D, 4 of which (44,505 participants) were at low risk of bias, risk estimates for total fractures were 0.89 and 0.96, respectively, and for hip fractures were 0.95 and 1.68, respectively. By 2018, from 36 trials of vitamin D (44,790 participants) the risk estimate for total fractures was 1.01, and from 20 trials (36,655 participants) the risk estimate for hip fracture was 1.11. From the same sets of trials, evidence emerged for adverse effects of calcium that are minor (gastrointestinal), moderate (hospitalization for gastrointestinal symptoms), and serious (kidney stones, myocardial infarction, stroke). Increases in falls and fractures were reported in some trials of high dose daily or intermittent vitamin D supplementation. Since randomized trials indicate that marginal benefit is balanced by adverse outcomes, calcium and/or vitamin D should not be prescribed for bone health.
Andrew Grey is an endocrinologist and Associate Professor of medicine at the University of Auckland, whose research interests include metabolic bone disease, research integrity, and research translation.