August 6 (HealthDay News) -- Physical activity can reduce the risk of colon cancer, but few American adults are aware of this, a new study shows.

A sedentary lifestyle accounts for as many as 14 percent of all colon cancer cases in the United States. People who get lots of exercise have a 30 percent to 40 percent lower risk of developing colon cancer, according to study co-author Elliott Coups, of the Division of Population Science at the Fox Chase Cancer Center in Cheltenham, Pa., and colleagues.

But their analysis of survey data from 1,932 adults who answered questions about colon cancer risk found that only 15 percent said they used physical activity as a way of reducing their colon cancer risk. The findings were published in the August issue of Patient Education and Counseling.

Several factors may contribute to this lack of knowledge about the link between exercise and colon cancer risk.

"Patients may not be learning this information from their health-care providers and information regarding colon cancer prevention is not as well publicized as it could be," Coups said in a new release from the Center for the Advancement of Health.

Doctors may find it easier to tell patients about the general health benefits of exercise, rather than specifically referring to colon cancer, even if a patient has a family history of colon cancer or other risk factors for the disease.

"In the context of busy clinic visits, it is, in some ways, efficient for patients to be reminded that physical activity is good for their health in general. Going through each specific health benefit of physical activity would take considerable time," said Coups.

Sedentary people can greatly benefit from starting a modest exercise program, such as gardening or walking two to three hours a week, according to Dr. Edward Giovannucci, a professor at the Harvard School of Public Health.

"Sedentary people should first set such moderate, achievable goals. More benefits could accrue from higher levels and more intense exercise, such as jogging, running or tennis. To some extent, more may be better, but it is important to note that a little is much better than nothing," Giovannucci said in the news release.

SOURCE: Center for the Advancement of Health, news release, July 17, 2008