Breast Cancer and Calcium Supplements

You may have heard that certain vitamin supplements can help you reduce your risk of breast cancer. One in particular that you've probably heard about is calcium supplements with vitamin D.

Many doctors say that women would do well to take a calcium supplement containing vitamin D in order to help prevent bone loss. The science for the current recommendations of 1200 milligrams per day may not be great, but there is some. The proof for calcium and breast cancer, however, doesn't appear to be nearly as good.

Over 33,000 postmenopausal women who were enrolled in the Women's Health Initiative were invited to participate in a study of calcium plus vitamin d supplements and their effect on the risk of hip fractures, colon cancer and breast cancer (J Natl Cancer Inst 2008; 100:1581-1591). These women had already been evaluated by clinical breast exam and mammogram and were free of breast cancer at the beginning of the Women's Health Initiative two years before.

Half of the women were given 1000 milligrams of calcium plus 400 IU vitamin D on a daily basis and the other half were given placebos that looked the same as the calcium/vitamin D pills. For an average of seven years these women were tracked and given regular mammograms as well as other appropriate medical tests and treatment. At the end of the seven years the researchers evaluated the medical records of the participating women to see if the incidence of breast cancer between the two groups was different.

They found that there was no significant difference in the risk of breast cancer between those women who were taking calcium and vitamin D supplements and those who were not. Nor was there any significant difference in the size of the cancers that were found – those women who were taking the supplements had tumors that were a very little bit smaller than those in the women who were not taking the supplements. The stages of the tumors found, however, were much the same.

What this means for you

Breast cancer is a very scary disease and it's natural to want to do everything you can to help prevent it. However, supplements, no matter what kind they are and how helpful they might be in preventing other conditions, are no substitute for eating healthy, maintaining a healthy weight, and exercising regularly.

First posted: February 11, 2009