Taking calcium supplements is associated with a decreased risk of advanced colon polyps, according to a new study. Although high calcium intake has been shown to inhibit colon cancer in animal experiments, these effects have not been seen consistently in human studies.

To explore in greater detail the chemopreventive effects of calcium supplementation, Kristin Wallace, MS, and John A. Baron, MD, of the Dartmouth Medical School analyzed data from 913 patients who took either a 1,200 mg calcium supplement or a placebo. All had a follow-up colonoscopy 1 and 4 years after enrolling in the trial.

The researchers found that supplemental calcium slightly decreased the risk of all types of colorectal polyps. The effect was greatest for the advanced lesions that are felt to be most strongly associated with invasive colorectal cancer. In addition, there was some evidence that a diet high in fibre and low in fat increased the preventive effect of calcium, but these results were not statistically definitive.

These findings “suggest that total calcium intakes above 1,200 mg are necessary, and perhaps that high dietary fibre and modest dietary fat are required to optimize this [anticancer] effect. Additional data regarding nutrient interactions with calcium will help further refine optimum cancer protective strategies and may clarify the mechanisms by which calcium has its effects in the large bowel,” the authors write.

Journal of the National Cancer Institute, Jun 15, 2004