June 15, 2004 - Calcium supplementation may help protect against advanced colorectal polyps, according to the results of a randomized trial published in the June 16 issue of the Journal of the National Cancer Institute.

"Clinical trials have shown that calcium supplementation modestly decreases the risk of colorectal adenomas," write Kristin Wallace, MS, from the Dartmouth Medical School in Lebanon, New Hampshire, and colleagues. "However, few studies have examined the effect of calcium on the risk of different types of colorectal lesions or dietary determinants of this effect."

Increased calcium intake has been shown in animal models to inhibit colon cancer, but this effect has not been consistently demonstrated in human studies. In this double-blind trial, 913 patients enrolled in the Calcium Polyp Prevention Study (CPPS) were randomized to receive a daily 1200-mg calcium supplement or a placebo. Patients had follow-up colonoscopy one and four years after enrollment.

Compared with placebo, supplemental calcium was associated with decreased risk of all types of colorectal polyps, especially for more advanced lesions most strongly associated with invasive colorectal cancer. Diets high in fiber and low in fat appeared to enhance the preventive effect of calcium, but this trend was not statistically significant.

"Our findings also suggest that total calcium intakes above 1200 mg are necessary, and perhaps that high dietary fiber and modest dietary fat are required to optimize this effect," the authors write. "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 National Cancer Institute and the National Institutes of Health supported this study.

Dr. Lemmo's Comments

References

1. J Natl Cancer Inst. 2004;96:893-894, 921-925