Much of the promise for cancer prevention comes from studies that show associations between… Much of the promise for cancer prevention comes from studies that show associations between modifiable lifestyle factors or environmental exposures and specific cancers.

The most consistent finding, over decades of research, is the strong association between tobacco use and cancers of many sites. Hundreds of studies have confirmed this association. Further support comes from the fact that lung cancer death rates in the United States have mirrored smoking patterns, with increases in smoking followed by dramatic increases in lung cancer death rates and, more recently, decreases in smoking followed by decreases in lung cancer death rates in men.

Viral infections may also be associated with cancer development. Human papillomavirus infection is a necessary event for subsequent cervical cancer, and vaccine-conferred immunity results in a marked decrease in precancerous lesions. Likewise, Epstein-Barr virus has been associated with Burkitt’s lymphoma and Helicobacter pylori with gastric cancer, although specific anti-infective interventions have not yet been proven effective in preventing these cancers.

Additional examples of modifiable cancer risk factors include alcohol consumption (associated with increased risk of oral, esophageal, breast and other cancers), physical inactivity (associated with increased risk of colon, breast and possibly other cancers) and obesity (associated with colon, breast, endometrial and possibly other cancers).

Observational evidence shows associations between amount of alcohol consumption, physical inactivity and obesity and increased incidence of certain cancers. More research is needed to determine whether these associations are causal and thus whether avoiding these behaviors would actually reduce cancer incidence.

In 2001, experts concluded that cancers of the colon, breast (postmenopausal), endometrium (the lining of the uterus), kidney and esophagus are associated with obesity. Some studies have also reported links between obesity and cancers of the gallbladder, ovaries and pancreas.

Obesity and physical inactivity may account for 25 to 30 percent of several major cancers – colon, breast (postmenopausal), endometrial, kidney and cancer of the esophagus.

Preventing weight gain can reduce the risk of many cancers. Experts recommend that people establish habits of healthy eating and physical activity early in life to prevent overweightness and obesity. Those who are already overweight or obese are advised to avoid additional weight gain, and to lose weight through a low-calorie diet and exercise. Even a weight loss of only 5 to 10 percent of total weight can provide health benefits.

Questions about artificial sweeteners and cancer arose when early studies showed that cyclamate in combination with saccharin caused bladder cancer in laboratory animals. However, results from subsequent carcinogenicity studies (studies that examine whether a substance can cause cancer) on these sweeteners and other approved sweeteners have not provided clear evidence of an association between artificial sweeteners and cancer in people.

This information is from the National Cancer Institute at www.cancer.gov.