New York City ? Calcium doesn’t just build strong bones, it may fight cancer too, a study said.

Researchers at the Ponce School of Medicine in Puerto Rico reported that women who took calcium had a 40 percent lower risk of getting breast cancer, while those getting multivitamins showed a 30 percent reduction in risk. The new findings, from a study of 744 women, were presented Sunday at the meeting of the American Association for Cancer Research in Washington.

The data contradict results of a December 2008 trial that showed no reduction in cancer risk from vitamin supplements. The scientists attributed the calcium benefit seen in the study to its effect on what they called DNA repair capacity — the biological process by which cells patch up damaged DNA that otherwise may cause cancer. The report suggests women may boost their cellular defenses with dietary changes and long-term use of supplements, they said.