Diet, smoking, exercise key in colon cancer risk

By Amy Norton

NEW YORK (Reuters Health) - People who want to reduce their risk of colon cancer may want to start exercising more and cutting down on red meat and alcohol, a new research review suggests.

Such measures -- along with not smoking -- may be key lifestyle choices in preventing the cancer, according to the analysis, which looked at more than 100 previous studies on colon cancer risk factors.

Overall, researchers found, high intake of red and processed meats, smoking, obesity and diabetes were all linked to a 20 percent increase in the risk of colorectal cancer. In contrast, people who exercised the most had a 20 percent lower risk of the disease than their sedentary counterparts.

Type 2 diabetes is closely linked to obesity, and both can be prevented or managed through a healthy diet and physical activity -- further highlighting the importance of lifestyle choices in colon cancer risk, the researchers report in the International Journal of Cancer.

As important as diet and exercise were, drinking habits emerged as the most significant lifestyle factor, according to the researchers, led by Dr. Rachel R. Huxley of the George Institute for International Health in Sydney, Australia.

Compared with adults who were light drinkers or teetotalers, those who averaged a drink a day or more had a 60 percent higher risk of colorectal cancer across the studies.

The key message, Huxley told Reuters Health, is that "colorectal cancer is a disease of lifestyle and that modifying inappropriate behaviors now -- such as reducing alcohol intake, quitting smoking and losing weight -- has the potential to substantially reduce a person's risk of the disease."

She added that this is likely to be true of all adults, including those who have a higher risk of colon cancer due to family history.

A 2007 report from the World Cancer Research Fund concluded that there was "convincing" evidence that obesity and high intake of red meat and alcohol contribute to colon cancer, Huxley's team notes. Studies on smoking and diabetes have been less consistent, however, and they acknowledge in the current study that many behaviors -- such as smoking, drinking alcohol, physical inactivity, and eating a diet high in meat -- tend to occur together, making the effect of each individual behavior difficult to measure.

The current findings, the researchers write, suggest that smoking and diabetes are as important in colon cancer risk as obesity and red meat consumption.

SOURCE: International Journal of Cancer, July 1, 2009.