Background: Women undergoing treatment for breast cancer are often prescribed calcium and vitamin D supplements to prevent and manage osteoporosis, an unwanted side effect of breast cancer management.
The Study: The authors reviewed data from clinical trials that evaluated the effect of antiresorptive drugs on BMD and used the “before-after” data from the comparison group to assess change in BMD in pre- and in post-menopausal women. Overall, the results from 16 trials indicate that 500-1500 mg calcium and 200-1000 IU vitamin D, the doses commonly recommended, do not prevent loss of BMD in women with breast cancer. Despite supplementation, women lost BMD in virtually every clinical trial reviewed.
My Take: Breast cancer patients lose bone mineral density at a higher rate than their healthier counterparts, increasing their risk of fractures (which are associated with significant declines in function and health-related quality of life, and in higher mortality rates). In the clinical trials reviewed, BMD in the women was measured at the beginning and end of the studies, one author said, “so if the supplementation worked to prevent BMD loss, you should be able to see that in the data, and we clearly didn’t.”
Maybe the bone loss would have been worse without the supplements, but this study is concerning as : 1) we do a poor job of slowing or stopping bone loss; and 2) there is growing evidence of a link between calcium supplements and the risk of a stroke or heart attack. (As an aside, I think that if you do take calcium supplements, it might be wise to divide the dosing; for example, take half in the morning and half in the evening, rather than all at once (bolus effect.) For now, we don’t have good data to guide patients with breast cancer when it comes to calcium and vitamin D. Certainly, a bit of weight-bearing exercise is a good idea for most of us.
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