Calcium and Vitamin D at 22 Years: Cancer Deaths Down 7%, Cardiovascular Deaths Up 6%, Total Deaths the Same

How does taking calcium and vitamin D together affect the long-term health of older women? In a follow-up of the Women's Health Initiative (WHI) calcium and vitamin D trial in the United States to a median of 22.3 years, effects differed by disease, and there was no difference in overall mortality. The research was led by the University of Arizona and others in the United States.

Seven Years of Randomisation, Then Long-Term Follow-Up

The original trial ran for 7 years at 40 U.S. centres, assigning 36,282 postmenopausal women with no history of breast or colorectal cancer 1 to 1 to daily 1,000 mg of calcium carbonate (400 mg of elemental calcium) with 400 IU of vitamin D3, or to placebo. This analysis is a post hoc analysis of follow-up data that continued after the intervention ended.

The supplement group had 7% fewer cancer deaths than the placebo group (1,817 vs. 1,943, hazard ratio 0.93), but 6% more cardiovascular disease deaths (2,621 vs. 2,420, hazard ratio 1.06). Total deaths were 7,834 vs. 7,748, a hazard ratio of 1.00. Because some people were already taking supplements on their own before the trial began, the estimate for cancer incidence varied greatly depending on this.

Hip fracture and cardiovascular outcomes were confirmed only in some participants, and the effects of calcium and vitamin D could not be separated. Because this is a post hoc analysis, the signal of increased cardiovascular deaths should also be seen not as a definitive conclusion but as a result that needs further validation.