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Study finds calcium supplements may reduce colon cancer risk

IOWA CITY, Iowa -- Researchers at the University of Iowa played a major role in an important study that showed calcium supplements might reduce the risk of colon cancer. The study results are published in the Jan. 14 New England Journal of Medicine.

The four-year study involved 832 people. More than 200 participants enrolled in the study at the UI, the largest group at any of the sites in the multi-center study.

Results of the clinical study demonstrate that supplementation with calcium can reduce the recurrence rate of large bowel adenomas (also called polyps) in people with a history of such growths in the colon. Even though the adenomas themselves are benign, they are often precursors to cancer.

The researchers found that the people who took the calcium supplements had fewer polyps re-develop. "Because they had fewer of the polyps return, they had a lower risk of developing colon cancer, " said Dr. Robert Summers, professor of internal medicine and a gastroenterologist at the UI Hospitals and Clinics. He was a member of the research team.

According to the American Cancer Society (ACS), colon and rectal cancers (often referred to collectively as colorectal cancer) were responsible for approximately 28,600 deaths among women and 27,900 deaths among men in the U.S. in 1998. In addition, the ACS estimated that there were 67,000 new cases of colorectal cancer among American women and 64,600 news cases among American men in 1998. Overall, colorectal cancer accounted for about 11 percent of new cancer cases reported in 1998 and was responsible for 10 percent of all cancer deaths in the U.S, making it the second leading cause of cancer deaths overall.

UI researchers collaborated locally with specialists at the Iowa City Veterans' Affairs Medical Center, Gastroenterology Associates of Iowa City, Internist P.C of Cedar Rapids, and PCI Gastroenterology in Cedar Rapids.

Participants in the study took either calcium carbonate supplements (1200 milligrams of elemental calcium) or an identical-looking placebo. Overall, there was a 19 percent decrease in the incidence of the recurrence of one polyp and a 24 percent decrease in the total number of polyps.

"This is the first study to conclusively show that we can do something to significantly lower someone's risk for developing colon cancer," Summers said. "Plus, taking calcium supplements is inexpensive, and it has the added benefit of helping to strengthen bones. Calcium won't prevent every case of colorectal cancer, but this is important news in the fight against the disease."

The researchers say while calcium supplements do reduce the recurrence rate of polyps, they do not eliminate the pre-cancerous lesions. Therefore, the findings of this study do not change the requirements that patients with adenomas receive follow-up colonoscopies (examinations of the colon) at regular intervals as recommended by their gastroenterologists. In addition, no one should take supplements of any kind on a long-term basis without first consulting a physician.

Even though these results are significant, the most important safeguard against developing colon cancer is screening sigmoidoscopy and colonoscopy. It is essential to discuss these issues with your personal physician.