Large WHI randomized trial testing whether daily calcium plus vitamin D supplementation prevents hip and other fractures in healthy postmenopausal women. 36,282 women aged 50 to 79 received 1000 mg calcium carbonate plus 400 IU vitamin D3 or placebo, followed a mean of 7 years. Asks whether routine supplementation in generally calcium-replete women reduces fracture risk.
The clinical rule here: do not reflexively prescribe calcium plus vitamin D to every postmenopausal woman expecting fracture prevention. This WHI trial studied a calcium-replete population (mean intake ~1150 mg/day) at a low vitamin D dose (400 IU). Under those conditions the primary hip-fracture result was null.
The teaching point is why it was null. Little room to improve in already-replete women, a subtherapeutic vitamin D dose, poor adherence (only 59% took the full dose), and low power because the observed fracture rate was half of projected.
Contrast this with Chapuy, who showed benefit in vitamin D–deficient institutionalized elderly women at 800 IU. The lesson: supplementation helps most in deficient, high-absolute-risk patients, not the general population.
Balance the marginal benefit against real harm: a 17% increase in kidney stones. Target older women (over 60), those with low intake, and adherent patients rather than treating everyone.
Large WHI randomized trial testing whether daily calcium plus vitamin D supplementation prevents hip and other fractures in healthy postmenopausal women. 36,282 women aged 50 to 79 received 1000 mg calcium carbonate plus 400 IU vitamin D3 or placebo, followed a mean of 7 years. Asks whether routine supplementation in generally calcium-replete women reduces fracture risk.
The clinical rule here: do not reflexively prescribe calcium plus vitamin D to every postmenopausal woman expecting fracture prevention. This WHI trial studied a calcium-replete population (mean intake ~1150 mg/day) at a low vitamin D dose (400 IU). Under those conditions the primary hip-fracture result was null.
The teaching point is why it was null. Little room to improve in already-replete women, a subtherapeutic vitamin D dose, poor adherence (only 59% took the full dose), and low power because the observed fracture rate was half of projected.
Contrast this with Chapuy, who showed benefit in vitamin D–deficient institutionalized elderly women at 800 IU. The lesson: supplementation helps most in deficient, high-absolute-risk patients, not the general population.
Balance the marginal benefit against real harm: a 17% increase in kidney stones. Target older women (over 60), those with low intake, and adherent patients rather than treating everyone.