Supplementation with lower-dose vitamin D and calcium is not an effective fracture prevention strategy for healthy postmenopausal woman, according to a draft recommendation from the US Preventive Services Task Force (USPSTF). The task force recommends that healthy postmenopausal women should not take such supplements for this purpose.
The recommendation is based on a USPSTF review of the evidence, which found that the data to date do not demonstrate that supplementation with lower daily doses of vitamin D (400 IU of vitamin D3 or less) and calcium (1000 mg calcium carbonate) prevent fractures in postmenopausal women who don't have other underlying health issues (http://tinyurl.com/3wuyzdm). In addition to not having the intended benefit, such supplementation also increased the risk of developing kidney stones. According to the USPSTF, 1 in 273 women who take these lower-dose vitamin D and calcium supplements for 7 years will develop kidney stones.
Kuehn BM. USPSTF: Taking Vitamin D and Calcium Doesn’t Prevent Fractures in Older Women. JAMA. 2012;308(3):225-226. doi:10.1001/jama.2012.7955