Although calcium supplements can decrease the risk of all types of colorectal polyps, calcium appears to have the greatest effect on advanced colorectal adenomas, according to an article in the June 16th issue of the Journal of the National Cancer Institute.

"Our results suggest that calcium supplementation may have a more protective effect on advanced adenomas than on other types of colorectal polyps," said Kristin Wallace, a graduate student who was the lead author on the study. "These findings highlight the need to consider 'polyp type' when assessing the efficacy of a given treatment."

John Baron, MD, lead investigator, said "Previous studies have demonstrated an association between calcium intake and moderate decreases in the risk of precancerous colorectal tumors, but this is the first randomized trial to evaluate the effect of calcium on different types of colorectal lesions."
Researchers analyzed data from 913 patients enrolled in the Calcium Polyp Prevention Study, in which participants were randomized to 1200 mg calcium supplement or daily placebo and had a follow-up colonoscopy one and four years after enrolling in the trial.

The results showed that supplemental calcium slightly decreased the risk of all types of colorectal polyps, but effect was greatest for the most advanced colorectal lesions. There was also some evidence that a diet high in fiber and low in fat increased the preventive effect of calcium, but those results were not statistically significant.