An ambitious new study has added considerable weight to the claim that exercise can lower the risk for colon cancer. Researchers at Washington University School of Medicine in St. Louis and Harvard University combined and analyzed several decades worth of data from past studies on how exercise affects colon cancer risk. They found that people who exercised the most were 24 percent less likely to develop the disease than those who exercised the least.

"What's really compelling is that we see the association between exercise and lower colon cancer risk regardless of how physical activity was measured in the studies," says lead study author Kathleen Y. Wolin, Sc.D., a cancer prevention and control expert with the Siteman Cancer Center at Barnes-Jewish Hospital and Washington University. "That indicates that this is a robust association and gives all the more evidence that physical activity is truly protective against colon cancer."

Colorectal cancer is the third most common type of cancer. Each year more than 100,000 people in the United States are diagnosed with colon cancer and about 40,000 are diagnosed with rectal cancer. The study suggests that if the American population became significantly more physically active, up to 24 percent, or more than 24,000, fewer cases of colon cancer would occur each year.

Wolin's report was published Feb…