Calcium May Prevent Polyps, But Effect on Cancer Still Not Known
Calcium Supplements and Polyps
Although calcium supplements might prevent development of polyps that sometimes lead to colon cancer, there is not enough evidence that the mineral can prevent colorectal cancer itself, according to a new study.
The study, a review of two earlier well-designed randomized controlled trials, found a moderate protective effect on development of colorectal adenomatous polyps, the small, generally benign types that about 30 percent of middle-aged and older Americans have. But "this does not constitute sufficient evidence to recommend the general use of calcium supplements to prevent colorectal cancer," says an Israeli team of researchers headed by Michael Asher Weingarten of Rabin Medical Centre.
Polyps can lead to colorectal cancer if unchecked. Because it is difficult to conduct studies on the effect of preventive doses of calcium on colorectal cancer itself -- due to the relatively small number of cases and the length of time they could be watched -- the reviewers looked instead at prevention of polyps, which occur frequently in the population, as a potential predictor of later cancer.
Previous experiments in animals and surveys of people who had high calcium diets have indicated a possible protective effect. In looking at the two best studies done so far, Weingarten and colleagues found results that "suggest a clinically relevant protective effect of dietary calcium supplementation on the development of colorectal adenomatous polyps."
"Although it is likely to be safe, this