Colon cancer is the second leading cause of cancer related death in the U.S. and the third most common malignancy in US women. Much research is being done on the prevention of colon polyps, which is thought to be the first step in the development of colon and rectal cancer. A large study by Dr. J. Baron revealed that calcium supplementation was associated with a significant reduction in the rate of recurrent colon and rectal polyps(1). This study used 1200 milligrams of calcium over a four-year period and found a 15% reduction in polyp recurrence. This reduction was seen within the first year of the study. Other studies have also revealed positive benefits from calcium supplementation and polyp protection. Therefore, consuming an adequate amount of calcium for optimal ‘bone health’ may also help to reduce the risk of colon and rectal malignancies.

In a second well controlled intervention study, Dr. Baron found reason for continued optimism regarding calcium and colon cancer prevention. In this study, 803 men and women who had a prior colon polyp were given calcium (1200 milligrams) or placebo and followed for 4 years. The investigators measured levels of vitamin D in the study participants and found that the benefit of calcium on polyp prevention was seen in individuals with higher levels of vitamin D(2).

In a new survey study by the American Cancer Society, they found an association between higher calcium intake and a lower risk of colon cancer for both men and women, while vitamin D might help cut risk in men. The association was strongest in people who took supplements, rather than getting these nutrients from foods. McCullough and her colleagues studied more than 60,000 men and more than 66,000 women who were already participating in an American Cancer Society study of nutrition and cancer prevention. The participants were all between 50 and 74-years old when they enrolled in the study in 1992 and 1993. People who took calcium supplements had about a 30% lower risk of developing colon cancer than people who did not take supplements(3).

In the future, more studies are needed to determine the exact amount of calcium and vitamin D needed for colon and rectal cancer prevention.

References:

(1) Calcium Supplements for the Prevention of Colorectal Adenomas
Baron, J.A., et al. N Engl J Med 1999; 340: 101-7.
(2) Grau MV, Baron JA, Sandler RS, et al. Vitamin D, calcium supplementation, and colorectal adenomas : Results of a randomized trial. J Natl Cancer Inst 2003;23:1765-71.
(3) Cancer Causes and Control (Vol. 14, No. 1: 1-12). http://www.cancer.org/docroot/NWS/content/NWS_2_1x_Study_Calcium_May_Reduce_Risk_Of_Colon_Cancer.asp