Calcium May Protect Against Colorectal Cancer

Jun 23, 2004 04:09 AM EDT

Recent research has found that taking calcium supplements may help prevent polyps in the colon, a risk factor for colorectal cancer.

The study, published in the June 16 issue of the Journal of the National Cancer Institute, found that supplements of the mineral seem to offer the most protection against the advanced polyps most strongly associated with invasive colorectal cancer.

Reduces risk up to 45%

Earlier research showed a 20% reduction in polyps with calcium intake.

But the new study found that with more advanced polyps, there was a more marked reduction, suggesting that calcium might have a more pronounced effect in preventing advanced polyps—reducing the risk of colorectal cancer 35% to 45%.

Most colon and rectal cancers begin as a polyp, a growth of tissue into the center of the colon or rectum. Removing polyps (also known as adenomas) early may prevent them from becoming cancerous.

1,200 mg supplement used

During the study, researchers analyzed data from 913 patients enrolled in the Calcium Polyp Prevention Study. Patients took either a 1,200mg supplement of calcium or a placebo, and had follow-up colonoscopies one and four years after they began the calcium therapy.

Compared with those on a placebo, people taking calcium supplements had fewer of all types of polyps. But the protective effect was most pronounced for the kind of advanced lesions that are most strongly associated with colon cancer. The risk for advanced polyps was reduced by about 35%.

May prevent cancer-promoting effects of bile acids

While it's not known exactly how the calcium may help prevent the polyps, researchers speculate that calcium prevents the irritating and cancer-promoting effect of bile acids and other fats in the bowel.

An estimated 106,370 new cases of colon cancer and 40,570 cases of rectal cancer will be diagnosed this year in the United States, according to the American Cancer Society, and about 56,730 deaths will result.


1. K. Wallace, JA. Baron; “Effect of Calcium Supplementation on the Risk of Large Bowel Polyps,” Journal of the National Cancer Institute, 2004: 96: 921-925.