Source: NEJM, February 16, 2006;354:669-683.
Research: Investigators in this study recruited 36,282 postmenopausal wo-men, aged 50 to 79 years, who were already enrolled in the Women's Health Initiative (WHI), and they randomized them to receive 1000 mg of elemental calcium as calcium carbonate with 400 IU of vitamin D3 daily or placebo. During an average follow-up period of seven years, fractures were ascertained and bone density was measured at three WHI centers. Nearly 2500 women received dual-energy x-ray absorptiometry scans of the lumbar spine, total hip, and total body. Bone mineral density was measured at annual visits two, six and nine.
Results: Compared with the placebo group, the calcium plus vitamin D group had higher hip bone density but the two substances did not reduce hip fracture risk. This lead researchers to conclude, "Among healthy postmenopausal wo-men, calcium with vitamin D supplementation resulted in a small but significant improvement in hip bone density, but did not significantly reduce hip fracture, and increased the risk of kidney stones."