Calcium supplements can lower risk of advanced colon polyps
polyps, appears to have the greatest effect on advanced colorectal
adenomas, considered to be most strongly associated to invasive
colorectal cancer, according to a multi-centre study.
"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 from US-based Dartmouth Medical School and lead author on the study. "These findings highlight the need to consider 'polyp type' when assessing the efficacy of a given treatment."
Colorectal polyps, or adenomas, are bumps or fleshy tumours that occur on the inside lining of the colon that may become cancerous over time. By decreasing the size of the polyps and their number, there is less potential for colorectal cancer.
The study, reported in today's issue of the Journal of the National Cancer Institute (vol 96, no 12, pp 921-925), builds on prior research and provides more evidence that calcium supplementation appears to be a relatively safe and inexpensive way to reduce the risk of the most serious types of colorectal polyps.
Cancer of the colon or rectum is the second deadliest form of cancer after lung cancer but is also considered one of the most preventable types of cancer, as there are several dietary factors that appear to play a protective role against the disease.
"Previous studies have demonstrated an association between calcium intake and moderate decreases in the risk of precancerous colorectal tumours, but this is the first randomised trial to evaluate the effect of calcium on different types of colorectal lesions," added project leader John Baron, professor of medicine and of community and family medicine at Dartmouth and an investigator at Norris Cotton Cancer Center at Dartmouth-Hitchcock Medical Center.
Researchers analysed data from 913 patients enrolled in the Calcium Polyp Prevention Study, a randomized, double-blind trial. Patients took either a 1200 mg calcium supplement or a 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 fibre and low in fat increased the preventive effect of calcium, but these results were not statistically definitive.
