Calcium Supplements Can Reduce the Risk of Colorectal Adenomas

29/01/07 Previous studies have shown that people with noncancerous colorectal tumors called adenomas who take calcium supplements for 4 years can reduce their risk of an adenoma recurrence. A new study shows that the protective effect of those supplements lasts for up to 5 years after stopping supplementation.

In the Calcium Polyp Prevention Study, 930 people with a recent adenoma were randomly assigned to receive 4 years of daily 1200-milligram calcium supplements or a placebo. The study revealed that those assigned to calcium supplements had a 17 percent lower relative risk of an adenoma recurrence than those who got the placebo.

In the new study, Maria V. Grau, M.D., and John A. Baron, M.D., of Dartmouth Medical School, and colleagues followed 822 of the patients from that trial after the end of the treatment. Their aim was to compare the risk of recurrence among participants who had taken calcium with the risk among those who had taken a placebo.

The researchers found that, in the first 5 years after the end of the treatment, people in the calcium group continued to have a lower risk of adenomas than those in the placebo group: 31.5 percent of people who had taken calcium had recurrences compared with 43.2 percent of those originally in the placebo group. However, after 5 years, this protective effect disappeared.

"Our study provides further evidence of the potential of calcium as a chemopreventive agent against colorectal adenomas among individuals with a history of these tumors," the authors write. "Our data indicate that, in these patients, the protective effect of calcium may extend for up to 5 years after the cessation of active treatment."

"Where do we go from here--and, more important, what public health recommendations related to calcium do we provide for risk reduction of colorectal cancer?" ask editorial writers María Elena Martínez, Ph.D., and Elizabeth T. Jacobs, Ph.D., of the Arizona Cancer Center in Tucson. They note that current guidelines recommend that people simply consume recommended levels of calcium (1000 mg/day for adults up to age 50 years and 1200 mg/day for those older than 50 years). "Because no protection for colorectal cancer is apparent at higher levels of calcium intake, this recommendation is justified," they write.