A review of 45 prospective studies found that risk for suffering colon cancer is increased by drinking alcohol and eating red meat, and decreased by eating more fiber and yogurt (JAMA Netw Open, Feb 16, 2021;4(2):e2037341). More than 1.3 million North Americans have had colorectal cancer, a disease associated with lifestyle factors that cause bad bacteria to thrive in your colon:
• eating a lot of red meat (meat from mammals), processed meats, sugar added foods, sugared drinks and fried foods
• not eating enough fruits, vegetables, nuts and whole grains
• not exercising
• being overweight
• smoking
• drinking alcohol

People diagnosed with colon cancer that had already spread from the colon, who changed to a more healthful diet and exercise program, had a 42 percent lower risk of dying over seven years, compared to those who did not change their lifestyles (JAMA Oncol, April 12, 2018). The American Cancer Society (ACS) Nutrition and Physical Activity Guidelines for Cancer Survivors recommend these lifestyle changes: follow a plant based diet with a variety of vegetables, fruits, whole grains and other seeds; avoid red meat and processed meats; avoid being overweight; and exercise regularly.

Gut Bacteria May Explain All of the Colon Cancer Risk Factors
What do these have in common: excess weight, lack of exercise, and eating certain foods known to increase risk for colon cancer? All of these behaviors affect the kinds of bacteria that grow in your colon. Your colon contains trillions of bacteria that help to control your digestion and just about everything that happens in your body. What you eat determines the types of bacteria that thrive in your gut. Certain types of bad gut bacteria, such as Fusobacteria, increase colon cancer risk, while some good types of bacteria can help to decrease risk. Fusobacteria are associated with suppression of a person’s natural immunity and activation of growth pathways to form colon cancer cells. See Colon Cancer, a Preventable Disease? and Colon Cancer, Gut Bacteria and Diet

Red Meat and Processed Meats: Many studies associate eating mammal meats with increased colon cancer risk (Colorectal Cancer 2011 Rep Lond WCRF/AICR, 2011:1-40). A prospective study of 32,147 women followed for an average 17.2 years found that avoiding red meat was associated with a statistically significant decreased risk for distal colon cancer and a non-statistically significant decreased risk for total colon cancer (International Journal of Cancer, April 1, 2018). A prospective study of Seventh Day Adventists found that people who eat fish and avoid red meat have a reduced risk for colon cancer (JAMA Intern Med, 2015;175:767-76). Those who eat meat regularly have a higher risk for colon cancer than those who eat fish and no meat, or those who eat meat less than once a week (Sci Rep, 2015;5:13484). The World Health Organization (WHO) reported that eating processed and red meat increases risk of colorectal cancer (J Gastroenterol, Dec 2, 2016; British Medical Bulletin, Dec 23, 2016; J Hum Nutr Diet, Jun 14, 2016; Br Med Bull, Dec 18, 2016).

Overweight: Colon cancer is far more common in people who are overweight, a major risk factor for having high blood sugar levels and diabetes. Obese people have different bacteria in their colons than skinny people do (Nature, 2009;457:480-484). Gaining excess weight is associated with having certain colon bacteria that increase the absorption of more calories from your colon (Nature, 2006;444:1027-1031). See How Gut Bacteria Affect Weight People with markers of high blood sugar called metabolic syndrome are at more than double the risk of developing colon cancer (Cancer Epidemiology, Biomarkers & Prevention , Feb, 2017). Eating sugar added foods and red meat may increase colon cancer risk by causing a fatty liver that causes high blood sugar levels (J Hepatol, Mar 19, 2018).

Lack of Exercise: A prospective study of 226,584 participants over age 45 found that both being overweight and not having an exercise program are independent risk factors for colon cancer (BMC Public Health, March 6, 2018). Other studies show that sitting more than 11 hours each day is associated with increased colon cancer risk (Br J Cancer, Mar 3, 2015;112(5):934-942). Exercising regularly reduces an overweight person’s chances of developing colon cancer (Med Sci Sports Exerc, 2002;34(6):913-9). Exercising regularly also reduces colon cancer risk in people who sit for long periods each day (Lancet 2016;388(10051):1302-10; Cancer Epidemiol Biomark Prev, 2010;19(11):2691-709).

My Recommendations
The same lifestyle habits that increase risk for heart attacks also increase risk for obesity, diabetes and certain cancers, particularly colon cancer. All of the risk factors for colon cancer are associated with increased numbers of bad bacteria called Fusobacterium in the colon. You can reduce your risk for colon cancer by:
• avoiding red meat and processed meats, fried foods, sugar-added foods and drinks with sugar in them
• avoiding smoke and alcohol
• maintaining a healthful weight
• exercising regularly