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WHI: Calcium plus vitamin D failed to reduce hip fracture, colorectal cancer risk
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Calcium and vitamin D supplementation did not decrease the risk for hip fracture or colorectal cancer after an average of 11 years, according to new data from the Women’s Health Initiative. Rather, exploratory analyses found an incidence of lower vertebral fracture and in situ breast cancer in the supplement users.
Jane A. Cauley, DrPH, of the University of Pittsburgh, and colleagues gathered these outcome results approximately 5 years after the intervention was stopped and analyzed the cumulative findings.
“This post-intervention study from the WHI contributes new data on the long-term effects of calcium plus vitamin D supplementation on health outcomes,” Susan G. Kornstein, MD, editor-in-chief of Journal of Women’s Health, executive director of the Virginia Commonwealth University Institute for Women’s Health, and president of the Academy of Women’s Health, said in a press release.
Postmenopausal women (n=36,282) were randomly assigned to vitamin D supplementation or placebo; post-intervention follow-up continued among 29,862 (86%) of surviving patients.
It was determined that the risk for hip fracture was comparable in the supplement and the placebo groups during post-intervention (HR=0.95; 95% CI, 0.78-1.15) and overall (HR=0.91; 95% CI, 0.79-1.05).
The risk for colorectal cancer did not differ between groups, according to data (HR=0.95; 95% CI, 0.8-1.13). There also was no difference in invasive breast cancer, cardiovascular disease and all-cause mortality between groups, researchers wrote.
Further subgroup analyses revealed that the invasive breast cancer effect varied by baseline vitamin D intake (P=.03 for interaction); women with vitamin D intakes of more than 600 IU per day demonstrated an increased risk for invasive breast cancer (HR=1.28; 95% CI, 1.03-1.6), according to data.
Post-hoc analyses showed that the incidence of vertebral fractures (HR=0.87; 95% CI, 0.76-0.98) and in situ breast cancers (HR=0.82; 95% CI, 0.68-0.99) were lower among women randomly assigned to vitamin D supplementation, researchers wrote.
Future research should investigate the relationships between vertebral fractures and in situ and invasive breast cancers, including potential mechanistic studies, Cauley and colleagues wrote.
Disclosure: The researchers report no relevant financial disclosures.
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