One in 20 North Americans can expect to develop colon cancer, with more than 100,000 new cases each year. A recent review of 80 studies found that most cases of colon cancer are linked to poor lifestyle choices (BMJ Gut, Sept, 2020). Dietary and medication factors that reduce colon cancer risk include:
• fruits and vegetables, associated with 52 percent reduced risk
• fiber, associated with 22-43 percent reduced risk
• aspirin appears to lower the risk by 14-29 percent at doses as low as 75 milligrams/day
• non-steroidal drugs (NSAIDs), taken for up to five years, are associated with 26-43 percent reduced risk
• high intake of folic acid, associated with up to 15 percent reduced risk
• dairy products appear to reduce risk by 13-19 percent, but this is still controversial
• several studies report reduced risk with magnesium, folate, beta carotene, or selenium

Factors that were found to increase colon cancer risk include:
• Meat, particularly meat from mammals and processed meats. One of the studies showed that each daily 50-gram portion of processed meat is associated with an 18 percent increase in colon cancer risk (BMJ, Feb 14, 2018;360:K322).
• Alcohol, with one or two drinks per day associated with increased risk.

The researchers found no proven effect on colon cancer risk from tea, coffee, garlic, onions, fish, soy products, vitamins E or C, multivitamins, high calcium intake or statin drugs. One study that followed 60,000 Chinese men for almost 10 years found that consumption of saturated fatty acids, monounsaturated fatty acids or polyunsaturated fatty acids were not significantly associated with colon cancer risk (International J of Cancer, July 7, 2020).

How Your Diet Affects Your Chances of Developing Colon Cancer
The leading theory on the cause of colon cancer is based on inflammation, and everything you do to reduce inflammation can help to prevent and treat colon cancer. When a germ gets into your body, your immune system produces cells and chemicals that try to attack and kill that germ. Then when the germ is gone, your immune stystem is supposed to dampen down. If your immune system stays active all the time (inflammation), it uses these same cells and chemicals to attack and damage your tissue, which can cause heart attacks, certain cancers and premature death.

What you eat and other lifestyle factors determine the types of bacteria that live in your colon, with healthful bacteria helping to reduce inflammation and harmful bacteria promoting inflammation (J of Medical Microbiology, Sep 18, 2019;68(10); World J Gastrointest Oncol, Mar 15, 2018;10(3):71-81). High concentrations of a family of bacteria called Fusobacterium were found in most colon cancer tissues removed from more than 1000 people during cancer surgery (J of Biosciences and Medicines, 2018;6:31-69). Another study of almost 140,000 people showed that the typical Western diet, high in sugar and meat, is strongly associated with colon cancers in people whose colons harbor Fusobacterium nucleatum (JAMA Oncol, January 26, 2017). A diet rich in soluble fiber helps to reduce the growth of Fusobacterium in your colon (JAMA Oncol, 2017 Jul 1;3(7):921-927). After just two weeks on a diet restricting red meat and adding lots of fruits, vegetables, beans and seeds, a group of African-Americans had a significant reduction in specific colon bacteria and other risk factors for colon cancer (Nature Communications, April 28, 2015).

Cancer of the colon is also associated with eating a lot of refined carbohydrates found in sugared drinks, sugar-added foods, bakery products and pastas. These foods cause high rises in blood sugar that cause your pancreas to release large amounts of insulin and insulin-like-growth-factor-1. Both of these hormones increase cancer risk by increasing cell growth. Furthermore, refined carbohydrates in bakery products and pastas are constipating, which prolongs contact between food and the inner surface of the colon (Cancer Epidemiology Biomarkers & Prevention, 2001;10(7):725-731). Whole grains appear to help prevent colon cancer by sweeping foods and carcinogens through the colon at a faster rate.

Mammal Meat and Processed Meats Increase Colon Cancer Risk
Meat from mammals and processed meats promote the growth of harmful bacteria that try to invade your colon cells to cause inflammation (Am J Gastroenterol, May 1999;94(5):1373-80) and increase risk for colon cancer (JAMA Oncology, Jan 18, 2018). Mammal meat includes beef, veal, pork, lamb, mutton, horse, and goat. A prospective study of 32,147 women followed for an average of 17.2 years found that a red-meat-free diet was associated with a statistically significant decreased risk for distal colon cancer and a non-statistically-significant decreased risk for all colon cancers (International Journal of Cancer, April 1, 2018). Many other studies associate eating mammal meats with increased colon cancer risk (Colorectal Cancer 2011 Rep Lond WCRF/AICR, 2011:1-40). A Seventh Day Adventist study found that people who eat fish and avoid red meat have a reduced risk for colon cancer (JAMA Intern Med, 2015;175:767-76). Another study shows that 992 people who were already diagnosed with colon cancer that had spread beyond the colon, and changed to a healthier diet and exercise program, had a 42 percent lower risk of dying over the next seven years compared to those who did not change their lifestyles (JAMA Oncol, April 12, 2018).

How Soluble Fiber Can Help to Prevent Colon Cancer
You cannot absorb soluble fiber and other resistant starches (from plants) in your upper intestinal tract, so they pass to your colon, where bacteria ferment them to generate short chain fatty acids (SCFAs) that reduce inflammation (Proc Nutr Soc, 2015;74:23-36). SCFAs can also cause your colon to produce thick mucus that keeps harmful bacteria from growing in your colon.

Other Inflammatory Lifestyle Factors That Increase Colon Cancer Risk
A study in Gastroenterology (December 2018;155(6):1805-1815.e5) found that colon cancer is also associated with other lifestyle factors that increase inflammation, including:
• lack of exercise,
• overweight,
• smoking, and
• alcohol consumption.
The authors of another study of 13,600 screening colonoscopies showed that these same factors are strongly associated with increased risk of all stages of colorectal cancers at time of diagnosis (International Journal of Cancer, November 23, 2018).

Smoking increases risk for developing colon cancer and those who smoked at the time of colon cancer diagnosis were 47 percent more likely to have a recurrence of colon cancer or to die from that disease (JNCI, Dec 6, 2000;92(23):1888-1896). Smoking produces tremendous amounts of free radicals that can enter your bloodstream and travel to and enter every cell in your body to damage the DNA to cause cancers. Alcohol also is a potent carcinogen that can damage cellular DNA (Gut, 2003 Jun; 52(6): 861-867).

My Recommendations
The same lifestyle factors that increase risk for colon cancer also increase risk for several other types of cancers, heart attacks, strokes, obesity, diabetes and dementia, so making the lifestyle changes recommended to reduce colon cancer risk will also help to protect you from most of the major diseases that are associated with aging.
• Follow a plant-based diet with plenty of vegetables, fruits, nuts, whole grains, beans and other seeds
• Avoid or restrict mammal meat, processed meats, sugar-added foods, sugared drinks and fried foods
• Try to exercise every day
• Maintain a healthful weight
• Avoid smoking, alcohol, unnecessary drugs and other toxic substances