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Colorectal Cancer Health Center

Calcium May Reduce Colon Cancer Risk

Calcium seems to protect high-risk people from developing the polyps that can lead to colorectal cancer -- and the benefits appear to last long after calcium supplementation ends.
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WebMD Health News
Reviewed by Louise Chang, MD

Jan. 16, 2007 -- Calcium seems to protect high-risk people from developing the polyps that can lead to colorectal cancer -- and the benefits appear to last long after calcium supplementation ends.

Patients with a history of nonmalignant polyps took either 1,200 milligrams of calcium in supplement form or a placebo daily for four years in a study previously reported by researchers from Dartmouth Medical School. Calcium use was associated with a 17% lower relative risk for polyp recurrence.

This risk reduction not only persisted in the years after treatment ended, but it seemed to strengthen, the Dartmouth researchers report in a newly published follow-up that included 822 of the 930 original study subjects.

During the first five years after the end of treatment, 31.5% of patients in the calcium group developed new polyps, compared with 43.2% of the study participants who did not take calcium. The protection did not appear to extend beyond five years, however.

The findings are published in the Jan. 17 issue of the Journal of the National Cancer Institute.

"It really does look like calcium interferes with carcinogenesis [cancer development] in the large bowel," researcher John A. Baron, MD, tells WebMD. "The fact that this reduction in risk persisted for years after people stopped taking calcium is really amazing."

Polyps are growths in the colorectal area. Some polyps can become cancerous tumors.

But Baron says it is still not clear if the benefits of taking calcium supplements outweigh the risks among men because some studies have linked the treatment to an increase in prostate cancer risk.

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