Supplemental calcium carbonate protects against all types of colorectal polyps, but the antineoplastic effect seems to be greatest for histologically advanced colorectal lesions, those most likely to progress to cancer, according to a new study.
In the randomized double-blind, placebo-controlled Calcium Polyp Prevention Study, patients took either a 1200 mg calcium supplement or a placebo supplement daily.”These new data makes it increasingly likely that calcium will have a protective effect on cancer itself, not just the benign precursor tumors,” Dr. John A. Baron, from the Dartmouth-Hitchcock Medical Center in Lebanon, New Hampshire told Reuters Health.Calcium supplementation has been tied to a modest reduction in the overall risk of precancerous colorectal adenomas. “However, few studies have examined at the effect of calcium on the risk of different types of colorectal lesions,” investigators note in the June 16th issue of the Journal of the National Cancer Institute.During 4 years follow up, 279 of 913 study subjects developed at least one hyperplastic polyp and 382 developed one or more tubular adenomas. “All types of polyps occurred less frequently in the calcium treatment group than in the placebo group,” the investigators report. Considered together, the risk for all adenomas was modestly reduced in the calcium group, with a risk ratio of 0.86. However, the individual risk reductions for hyperplastic polyps and tubular adenomas were not statistically significant. The chemopreventive effect of calcium “seemed particularly pronounced” for histologically advanced neoplasms, with a calcium risk ratio of 0.65 compared with placebo.The findings also suggest that a total daily calcium intake greater than 1200 mg as well as a high intake of dietary fiber and a low intake of fat is needed to “optimize” the chemopreventive effects of calcium.Commenting on the findings, Dr. Baron said: “Calcium is not a sexy drug, and to some people, it might seem implausible that something as simple and familiar as calcium might lower the risk of a major cancer. This new research shows that the calcium effect is particularly pronounced for advanced adenomas, those with the closest connections to cancer.”The authors of an editorial remind readers that this study does not prove a causal link between calcium intake and colorectal cancer. However, according to Dr. Arthur Schatzkin and Ulrike Peters of the National Cancer Institute in Bethesda, Maryland, “studies are now in place with the potential to provide a compelling – almost proven – case that a nutritional factor (calcium) can alter the occurrence of malignant disease (colorectal cancer).”That would be a tremendous advance,” they write.(SOurce: J Natl Cancer Inst 2004;96:893-894,921-925: Reuters Health News: Megan Rauscher: Oncolink: June 2004)