Calcium’s lingering effect slows growths

From Anaheim, Calif., at a meeting of the American Association for Cancer Research

Taking calcium supplements protects against colorectal cancer even years after a person stops taking them, a study finds.

Starting in the early 1990s, scientists randomly assigned 930 patients with a history of precancerous growths in the colon or rectum to receive either a daily calcium tablet or an inert pill. Researchers ended the calcium supplementation in 1997.

Over the subsequent 5 years, participants regularly completed follow-up questionnaires about health and lifestyle, and 597 participants had colonoscopies. The data showed that people who had been in the calcium group had only two-thirds as many precancerous colorectal growths, often called polyps, as did people in the placebo group, says John A. Baron of Dartmouth Medical School in Hanover, N.H.

The role of diet in cancer is poorly understood, Baron notes. For example, some research suggests that calcium supplements might increase the risk of prostate cancer, although Baron’s data suggest the opposite. “This issue needs to be put to rest before we [can] make a broad recommendation” regarding calcium supplements, he says.