The benefits of calcium not only apply to the strength of bones. A study published in the American Journal of Clinical Nutrition (November 2004 80(5):1358-1365) shows that high calcium intake from supplements reduces the risk of cancer of the distal colon and rectum. The authors state that "Calcium can reduce risk of colorectal tumors by binding bile and fatty acids in the bowel, thus reducing exposure of colonic epithelium to these potentially carcinogenic compounds." Previous studies have shown that calcium supplementation can reduce recurrence of adenomas. There has been conflicting evidence from epidemiologic data regarding the effect of calcium intake in lowering risk of colon cancer, so researchers conducting the present study aimed to definitively answer whether calcium can reduce the risk.
A large study was conducted comparing calcium intakes in nearly 3700 patients with confirmed adenomatous polyps of the distal colon and almost 35000 control subjects who had negative sigmoidoscopys. Calcium intake was quantified by questionnaire including dietary and supplemental intake. The results showed that the risk of distal adenoma was decreased with increasing total calcium intake (supplemental plus dietary calcium) after adjustment for possible confounding factors. Interestingly, the authors observed that the associations were strongest for calcium from supplements and nondairy food sources.
Three other randomized clinical trials also support the results of this study. These other studies examined the effect of calcium supplementation in the range of 1200-2000mg daily. The authors of the study are uncertain why dietary non-dairy calcium sources only offer moderate protection and calcium derived from dairy sources has no effect. However, they do state that "milk and dairy products also contain components that possibly trigger the development of cancer, such as saturated fat or insulin-like growth factor I." What we can take away from this study is the importance of calcium supplementation, not only for increasing bone density, but also for reducing the risk of colon cancer.
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