Colorectal cancer is the second most common cause of cancer-related deaths in the United States. Following screening recommendations is essential to prevention, but lifestyle choices are also important.
Are You at Risk? Cancers of the colon and the rectum are often grouped together as colorectal cancer. This cancer is more common in people over age 50, Jews of Eastern European descent, and Black adults. Most colorectal cancers begin as growths called polyps. If you have a personal or family history of polyps or colorectal cancer, or if you have an inflammatory bowel disease, you may be at increased risk. Additionally, people who have type 2 diabetes are diagnosed with this cancer more often than people who don’t.
While some of these factors are out of your control, lifestyle choices have a major impact on your chances of getting colorectal cancer. Being sedentary, smoking, and excess alcohol intake increase risk. Excess body weight is also a risk factor. “Each five additional points on the Body Mass Index (BMI) scale is associated with a five percent increase in the risk of developing colorectal cancer,” says Fang Fang Zhang, MD, PhD, a cancer epidemiologist and associate professor at the Friedman School.
This cancer also has a strong tie to food choices. In 2019, Zhang and her colleagues published a paper estimating the annual number of new cancer cases in the U.S. attributable to certain dietary factors. Of all cancers, colorectal cancer had the largest number and proportion of diet-related cases. “Our results suggest there are more than 52,000 new cases of colorectal cancer each year due to poor diet among U.S. adults,” says Zhang, “and the burden is particularly high among low-income Americans.”
Dietary Danger. Too much of some foods and too little of others is clearly linked to increased colorectal cancer risk. “In our study, consuming red and processed meat was associated with increased risk,” says Zhang. “whereas consuming whole grains, foods containing dietary fiber, and dairy foods was associated with lower risk. An overall poor dietary pattern, characterized by a low consumption of fruits and vegetables and a high consumption of sugar-sweetened drinks, may also increase colorectal cancer risk.”
Processed meats: “Regular intake of processed red meats (like cold cuts, bacon, sausage, and hot dogs) is associated with higher risk of colorectal cancer,” says Joel Mason, MD, lead scientist on the Vitamins and Carcinogenesis Team at the Jean Mayer USDA Human Nutrition Research Center on Aging, “and the evidence indicating it is a true causal factor is compelling.” The nitrites used to cure these meats contribute to the formation of carcinogenic (cancer-causing) compounds. Products marked “no nitrates or nitrites added’’ still contain nitrites from an alternate form, such as cultured celery juice or sodium nitrate. The total amount in some of these products can be higher than in conventionally cured meats. According to the American Cancer Society, unprocessed red meats (beef, pork, and lamb) have also been associated with higher colorectal cancer risk, although this continues to be a matter of debate.
Alcohol: The more alcohol you consume beyond one drink a day, the greater your colorectal cancer risk. Alcohol (ethanol) is metabolized in the body to acetaldehyde, which is a known carcinogen. The metabolism of alcohol also creates free radicals—unstable atoms that steal electrons from other atoms to bring themselves back into balance. Stealing from DNA can damage it in ways that increase cancer risk. It is possible that alcohol also acts as a solvent that makes it easier for carcinogens to penetrate the cells lining the colon.
Sugar-sweetened beverages (SSB): High SSB consumption can increase cancer risk through weight gain, as well as possibly through higher risk of diabetes. “Consumption of sugar-sweetened beverages is known to contribute to obesity,” says Zhang, “and obesity is a known risk factor for cancer.”
Dietary fiber: Although some large studies have shown conflicting results concerning the impact of dietary fiber on colorectal cancer risk, the fiber in fruits, vegetables, whole grains, beans, lentils, and nuts slows digestion, which may help with maintenance of body weight, and contributes to a healthy microbiome, which may lower risk of cancer.
Whole grains: A higher intake of whole grains is associated with lower risk of colorectal cancer. Whole grains contain a wide variety of nutrients with important health benefits and are an excellent source of dietary fiber.
Fruits and vegetables: These healthy choices contain fiber and an array of vitamins, minerals, and phytonutrients to help keep your body healthy.
Dairy products: Consuming dairy foods is associated with a lower risk of developing colorectal cancer. “This is possibly attributed to the calcium content of dairy foods,” says Zhang.
What to Do. “The high number of diet-attributed colorectal cancer cases reinforces the importance of eating a healthful diet for colorectal cancer prevention,” says Zhang. In general, the American Cancer Society and other experts recommend limiting red and processed meats and eating more vegetables, fruits, and whole grains to help lower your risk. The components of this dietary pattern are consistent with those recommended for the prevention of heart disease and type 2 diabetes.
Other lifestyle choices that may lower colorectal cancer risk include getting regular physical activity and avoiding exposure to tobacco products.
The most important thing you can do is get screened. Screening is recommended every 10 years, starting at age 45. If you have been told by your healthcare provider you are in a high risk category (due to personal or family history of polyps or colorectal cancer, for example) you may start sooner and be tested more frequently. A colonoscopy—examining the rectum and colon with a camera at the end of a long, flexible tube—is the most accurate test available to date, although there are other forms of screening available.
Lower your risk for cancer of the colon or rectum—and improve your health in general—by starting your shift to these dietary and lifestyle choices today.