Calcium supplements may not aid breast cancer
New research indicates that recommended daily doses of calcium and vitamin D supplements might not prevent loss of bone mineral density in women undergoing breast cancer treatment.
• Calcium and vitamin D supplements are widely prescribed to women undergoing treatment for breast cancer to prevent and manage osteoporosis. Many breast cancer therapies, such as oophorectomy, chemotherapy, and aromatase inhibitors, that reduce estrogen levels also increase bone resorption without a corresponding increase in bone formation. This leads to loss of bone mineral density.
• Emerging controversial evidence suggests that calcium supplements might increase the risk of heart attack and stroke.
Calcium and vitamin D supplements are widely prescribed to women undergoing treatment for breast cancer to prevent and manage osteoporosis. Why? Many breast cancer therapies, such as oophorectomy, chemotherapy, and aromatase inhibitors, that reduce estrogen levels also increase bone resorption without a corresponding increase in bone formation. This situation leads to loss of bone mineral density (BMD).3,4
Compared to healthy postmenopausal women who might lose about 1% of BMD per year, women with breast cancer might drop two to three times more, which increases the risk for fractures, including fractures at an early age.4-5
New research from scientists at Wake Forest Baptist Medical Center in Winston-Salem, NC, however, indicates that the recommended daily doses of calcium and vitamin D supplements might not prevent loss of bone mineral density in women undergoing breast cancer treatment.6 Future trials are needed to evaluate the safety and efficacy of calcium and vitamin D supplementation in women undergoing breast cancer therapy, researchers say.
Why are women undergoing therapy for breast cancer at increased risk for bone loss? The answer is simple, says Gary Schwartz, PhD, a cancer epidemiologist at Wake Forest Baptist and study coauthor. "Estrogen helps to build bone. This is why bone mineral density is lost following menopause, when a woman's estrogen levels are lower," observes Schwartz. "Because estrogen promotes the growth of many breast cancers, particularly those that are estrogen receptor positive, most therapies for breast cancer involve reducing estrogen levels or at least, inhibiting their effects."
To conduct the study, Schwartz and co-author Mridul Datta, PhD, a postdoctoral fellow at Wake Forest Baptist, conducted a systematic review of calcium and/or vitamin D supplementation trials for maintaining bone mineral density in women with breast cancer using the "before-after" data from the calcium plus Vitamin D supplemented comparison group of trials that evaluated the effect of drugs such as bisphosphonates on BMD.
Results from 16 trials included in the current analysis indicate that the calcium plus Vitamin D doses tested (500-1,500 mg calcium; 200-1000 international units [IU] vitamin D) were inadequate to prevent bone mineral density loss in these women.6Despite supplementation, women lost BMD in virtually every clinical trial reviewed, the analysis indicates.
Risk for heart health
Emerging controversial evidence suggests that calcium supplements might increase the risk of heart attack and stroke.7-8 Findings from a 2013 prospective longitudinal cohort study designed to investigate the association between long-term intake of dietary and supplemental calcium and death from all causes and cardiovascular disease indicate high intakes of calcium (intakes above 1,400 mg/day) in women are associated with higher death rates from all causes and cardiovascular disease, but not from stroke.9The study looked at a Swedish mammography cohort, a population-based cohort established in 1987-90, which followed 61,433 Swedish women who were born between 1914 and 1948 for a median of 19 years.9
What is the next step in research to evaluate the safety and efficacy of calcium and vitamin D supplementation in women undergoing breast cancer therapy?
"It is clear from our paper that low/moderate levels of calcium and vitamin D [cholecalciferol] supplements are ineffective in preventing loss of bone mineral density in women undergoing breast cancer treatment," says Datta. "Low dose of vitamin D hormone [1,25-Dihydroxyvitamin D] shows promise and needs to be evaluated further in preventing bone loss in these women."
REFERENCES
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2. Hadji P. Aromatase inhibitor-associated bone loss in breast cancer patients is distinct from postmenopausal osteoporosis. Crit Rev Oncol Hematol 2009; 69:73-82.
3. Hirbe A, Morgan EA, Uluçkan ö, et al. Skeletal complications of breast cancer therapies. Clin Cancer Res 2006; 12:6,309s-6,314s.
4. Kanis JA, McCloskey EV, Powles T, et al. A high incidence of vertebral fracture in women with breast cancer. Br J Cancer 1999; 79:1,179-1,181.
5. Edwards BJ, Raisch DW, Shankaran V, et al. Cancer therapy associated bone loss: implications for hip fractures in mid-life women with breast cancer. Clin Cancer Res 2011; 17:560-568.
6. Datta M, Schwartz GG. Calcium and vitamin D supplementation and loss of bone mineral density in women undergoing breast cancer therapy. Crit Rev Oncol Hematol 2013; doi:pii: S1040-8428(13)00152-2.
7. Holland MJ, Grey A, Avenell A, et al. Calcium supplements with or without vitamin D and risk of cardiovascular events: reanalysis of the Women's Health Initiative limited access dataset and meta-analysis. BMJ 2011; 342:d2040.
8. Li K, Kaaks R, Linseisen J, et al. Associations of dietary calcium intake and calcium supplementation with myocardial infarction and stroke risk and overall cardiovascular mortality in the Heidelberg cohort of the European Prospective Investigation into Cancer and nutrition study (EPIC-Heidelberg). Heart 2012; 98:920-925.
9. Michaëlsson K, Melhus H, Warensjö Lemming E, et al. Long term calcium intake and rates of all cause and cardiovascular mortality: community based prospective longitudinal cohort study. BMJ 2013; 346:f228.
