Colon cancer is the third most common cancer in the United States and the second most common cause of cancer-related death, according to the American Cancer Society. Most colorectal cancers arise from polyps in the colon, and removal of these polyps during a colonoscopy helps prevent their progression to cancer. Scientists are also studying other ways to reduce risk for colon cancer, such as daily doses of aspirin, vitamins or minerals.
Adenomatous Polyps
A December 2008 "American Family Physician" review reported that 30 percent of adults over the age of 50 had adenomatous polyps in their colon. Removing these polyps and/or preventing their occurrence significantly reduces your risk for colon cancer. A 2008 "Cochrane Database" review demonstrated that 1 g of dietary calcium daily may help to prevent adenomatous polyps from developing, but there is not enough evidence to support the notion that calcium supplementation will prevent colon cancer.
Differentiation
Healthy cells have the capacity to reproduce and form "offspring" that are similar in appearance and function to their parents. This ability of a specific cell type to retain its identity through successive generations is called "differentiation." Cancer cells lose this characteristic, with succeeding generations looking less and less like their progenitors. Hence, cancers are said to be "undifferentiated." A 2009 study published in "Cancer Epidemiology, Biomarkers and Prevention" showed that a daily 2 g dose of calcium improved cellular differentiation in the colons of individuals who already had adenomatous polyps. However, the authors conceded their findings did not prove that calcium prevents colon cancer.
Milk
Dietary and supplemental calcium appear to exert similar beneficial effects on the cells in your colon. A 2009 "Nutrition and Cancer" review suggested that individuals who consume more dairy products have a lower incidence of colon cancer than those who do not. High calcium intake from dietary and supplemental sources was associated with a lower risk for cancers in the lower colon and rectum. Vitamin D was associated with a "nonsignificant" reduction in colon cancer risk, but the review's authors noted that vitamin D intake was low among the study's subjects, so higher doses might confer more protection from colon cancer.
Considerations
Calcium appears to reduce the occurrence and recurrence of adenomatous polyps in the colon, but no clinical trial has yet demonstrated that calcium supplementation or high dietary calcium intake prevents colon cancer. Furthermore, some studies suggest that calcium intake in excess of 1,500 mg in men increases the risk for advanced and fatal prostate cancer. Current recommendations for daily calcium intake in adults range from 1,000 to 1,300 mg, depending on your age and pregnancy status. Ask your doctor if you should take more calcium.
References
- "CA, A Cancer Journal for Clinicians"; Cancer Statistics, 2008; A. Jemal et al.; February 2008
- "American Family Physician"; Colorectal Cancer: A Summary of the Evidence for Screening and Prevention; T. Wilkins, P.L. Reynolds; December 2008
- "Cochrane Database of Systematic Reviews"; Dietary Calcium Supplementation for Preventing Colorectal Cancer and Adenomatous Polyps; M.A. Weingarten et al.; January 2008
- "Cancer Epidemiology, Biomarkers and Prevention"; Effects of Vitamin D and Calcium on Proliferation and Differentiation in Normal Colon Mucosa: A Randomized Clinical Trial; V. Fedirko et al.; November 2009
- "Nutrition and Cancer"; Colorectal Cancer Risk and Dietary Intake of Calcium, Vitamin D, and Dairy Products: A Meta-analysis of 26,335 Cases From 60 Observational Studies; M. Huncharek et al.; 2009
- "Nutrition in Clinical Practice"; Calcium Supplementation in Clinical Practice: A Review of Forms, Doses, and Indications; D.A. Straub; June 2007
