(Ivanhoe Newswire) -- Calcium and vitamin D supplements do not protect postmenopausal women from breast cancer, a new study reveals.

Researchers randomly assigned 36,282 postmenopausal women to either a daily supplement containing 1,000 mg of calcium and 400 IU of vitamin D, or to a daily placebo. Both groups were found to have the same risk of invasive breast cancer. Almost 530 women in the supplement group developed the disease while 546 cases were reported in the placebo group.

25-hydroxyvitamin D levels were strongly linked to leanness and high physical activity, which both impact cancer risk. Previous studies relating vitamin D levels to breast cancer may have been affected by these factors.

"Because preclinical, epidemiological, and clinical trial results of vitamin D supplementation are conflicting, additional studies will be needed to determine whether vitamin D plus calcium will prevent breast cancer," Corey Speers and Powel Brown, M.D., Ph.D., of Baylor College of Medicine in Houston, wrote in an accompanying editorial. They say the study, however, "offers an important first step in addressing this issue," adding, "The potential health benefits of vitamin D and calcium may yet still have a bright future."

SOURCE: Journal of the National Cancer Institute, published online November 11, 2008

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