Lower Your Colon Cancer Risk with Calcium

Healthnotes Newswire (October 7, 2004)—Calcium supplements prevent the most serious types of colon polyps, and therefore colon cancer, according to the Journal of the National Cancer Institute (2004;96:921–5).

Colon polyps are growths that form inside the colon. Most have the potential to become cancer, with large polyps or those that show a high degree of cancerous change the most likely to progress. Colon cancer is the second most common cancer in Western societies. People with family members who have had colon cancer, and people with inflammatory bowel disease, such as Crohn’s disease and ulcerative colitis, are at high risk for colon cancer. Familial polyposis, an inherited condition characterized by frequent formation of colon polyps, also increases the risk of colon cancer.

A number of dietary factors might contribute to colon cancer risk. A diet that is rich in vegetables appears to be the most protective. In contrast, eating fried or darkly browned meat frequently more than doubles the risk of colon cancer, apparently because cancer-causing chemicals form during high-temperature cooking of meat. Some studies have found that increasing dietary fiber can reduce the risk of colon cancer, but other studies have failed to confirm those reports. A number of studies have suggested that calcium might prevent colon cancer. Some, but not all, have found that taking calcium supplements can lower the risk of developing colon cancer and precancerous polyps.

In the current study, 913 people who had at least one colon polyp surgically removed participated. They had all had the surgery within three months prior to entering the study, and were polyp-free upon entry. Dietary intake of calcium, fat, and fiber was assessed for each person through the use of a food questionnaire, and each was then randomly assigned to receive either 1,200 mg of calcium carbonate per day or placebo. Colonoscopic exams to look for new polyps were performed one and four years after the start of the study, and polyps that were found were analyzed to determine their type, size, and degree of cancerous change. At the end of the study, the risk of developing colon polyps was found to be14% lower in people taking calcium than in those taking placebo. Moreover, calcium supplementation reduced the risk of the most serious forms of colon polyps by 35%.

The results of this study suggest that supplementing with calcium might provide some protection against precancerous colon polyps in people at high risk due to a previous history of polyps. They further show that polyps that form while taking calcium might be less likely to be the most serious type. Future studies are needed to confirm these results. For now, it is reasonable to recommend calcium supplements to people who are at high risk of developing colon polyps.