Diets rich in calcium reduce women’s risk of colorectal cancer, and women who also take calcium supplements can cut their risk even more, researchers said on Thursday.

The protective effect of calcium likely works in men as well as women, though dairy products rich in calcium are also known to heighten the risk of prostate cancer, doctors from the University of Minnesota Cancer Center said.

Roughly 150,000 people in the United States are diagnosed with colorectal cancer annually, and it ranks second to lung cancer as the leading cause of cancer death, the report published in the journal Cancer Epidemiology, Biomarkers and Prevention said.

Of the more than 45,000 cancer-free women surveyed at the start of the study, 482 developed colorectal cancer after being tracked for an average of 8.5 years.

Those who consumed at least 800 milligrams of calcium daily had a 26 percent lower risk of the disease compared to women who consumed less than 530 milligrams.

Women who consumed more than 412 milligrams of calcium from dietary sources and also took more than 800 milligrams in supplement form had a 46 percent lower risk.

The U.S. government recommends a daily calcium allowance of 1,200 milligrams.

“Risk reduction was present regardless of the source of the calcium,” said study author Andrew Flood. “It was the calcium per se, and not merely dairy products or some other variable that accounted for the reduction in risk.”

One theory holds that calcium neutralizes bile acids produced during the digestion of fat that can irritate the cells lining the colon, he said. Or, calcium might act on the cells’ biochemical pathways that regulate how they grow and mature, and determine whether the cells become cancerous.