It is known that calcium supplementation lowers the risk of colorectal cancer. New findings from a study published in The Journal of the National Cancer Institute1 have determined the duration of the protective effect of this supplementation.
The researchers found a four-year intake of 1,200 mg of elemental calcium per day given to subjects with previous colorectal adenomas reduced their risk of recurrence of adenomas for a period of five years. The findings were consistent even in the absence of continued supplementation.
The authors state that this finding "suggests that a four-year course of calcium treatment alters the colorectal mucosa in such a way that it can resist the development of new adenomas that would otherwise become apparent several years later."
They offer two possible mechanisms to explain the results:
First, prior research has demonstrated calcium binds to bile acids and other free fatty acids in the gut. When these molecules are precipitated, they are rendered relatively inert and are unable to cause mucosal inflammation, and subsequent cellular proliferation. Interestingly, this theory was indirectly supported by another recent paper in the journal Cancer2 that showed both a decrease in fat intake and inflammation (via NSAID use) led to a lower incidence of adenomas. The researchers state "… total calcium intake of ≥ 900 mg/day was associated with a lower prevalence of adenomas among patients with lower fat intake but not among those with higher fat intake." In the author's words, "the data suggest that a lower-fat diet and regular NSAID use may enhance calcium's effectiveness as a colorectal cancer preventive agent."
The second possible mechanism is that colonocytes have been found to have a calcium sensing receptor (CaSR) that, when bound, might have anti-carcinogenic downstream effects.
With many Americans taking calcium supplementation for bone health, this research indicates a welcome beneficial "side-effect." It also appears this effect might be enhanced by the consumption of anti-inflammatory compounds and a low-fat diet.
In the Future-
Large Cohort studies are showing a negative correlation between dietary intake of magnesium and incidence of colorectal cancer in women.3,4 It's too early to tell, but it is possible magnesium supplementation will be of benefit as well.
1. Grau M, Baron J, Sandler R, et al. Prolonged Effect of Calcium Supplementation on risk of Colorectal Adenomas in a Randomized Trial. J Natl Cancer Inst 2007;99:129-136.
2. Miller E, Keku T, Sati J, et al. Calcium, Dietary, and Lifestyle Factors in the Prevention of Colorectal Adenomas. Cancer 2007;109:510-517.
3. Folsom A, Hong C. Magnesium intake and reduced risk of colon cancer in a prospective study of women. Am J Epidemiol 2006;163:232-235.
4. Larsson S, Bergkvist L, Wolk A. Magnesium intake in relation to risk of colorectal cancer in women. JAMA. 2005;293:86-89.
