Calcium lowers colon polyp formation up to 5 yrs

NEW YORK, Jan 17 (Reuters) Treatment with calcium supplements for four years appears to provide protection against recurrent colorectal adenomas -- the type of polyp that leads to cancer -- for up to five years after the supplements are stopped, new research shows. Beyond that point, however, no apparent effect is seen.

''In the Calcium Polyp Prevention Study, we showed that daily calcium supplementation was associated with a reduced risk of colorectal adenomas'' in patients with a previous adenoma, study co-author Dr John A Baron, from Dartmouth Medical School in Lebanon, New Hampshire, told Reuters Health. The current data from the Calcium Follow-up Study indicates that the beneficial effect is prolonged, he added.

Baron said that experimental studies have suggested calcium may reduce the risk of colorectal adenomas (and colorectal cancer) by forming a complex with bile acids and preventing potential carcinogens from contact with the inner mucosal lining of the colon.

He added that there is also evidence that calcium may have a specific effect on blocking formation of colon cells.

The Calcium Follow-up Study, which is reported in the Journal of the National Cancer Institute, included an analysis of data for 597 subjects who underwent at least one colonoscopy (a guided endoscopic colon exam to detect cancer) after the conclusion of the earlier Calcium Polyp Prevention Study. The average follow-up period after calcium supplementation stopped was seven years.

In the first five years of the study, the rate of any adenoma formation among former calcium users was 31.5 per cent, significantly lower than that of a comparison group of untreated patients at 43.2 per cent.

Previous calcium use was also associated with a reduced risk of advanced adenomas, but the association fell short of statistical significance.

As noted, beyond five years, previous calcium use had no apparent effect on the adenoma risk.

Baron said he would like to see the current findings replicated in other studies. He emphasized that it is too early to recommend calcium supplementation as a means of staving off colorectal cancer and noted that there is some evidence that such use may actually increase the risk of prostate cancer.

Reuters BDP GC0906