More than 1.3 million North Americans have had colorectal cancer, a disease associated with behaviors that encourage cancer-causing bacteria to thrive in your colon (Science, Feb 2, 2018:359(6375):592-597). Colon cancer is the second most common cancer cause of death in the United States today, yet it is rare in third world countries. The American Cancer Society reports that colon cancer has increased by 1-2.4 percent every year since the mid-1980s in individuals ages 20 to 39, and by 0.5-1.3 percent since the 1990s among those aged 40 to 54 (Digestive Disease Week, Nov 20, 2018, Washington DC).
Recently, several different studies have shown that certain lifestyle factors increase risk for colon cancer and that removing these factors helps to treat colon cancer. Colon cancer is linked to lifestyle factors that increase inflammation risk: an unhealthful diet, lack of exercise, excess weight, smoking, and alcohol consumption (Gastroenterology, December 2018;155(6):1805–1815.e5). The authors compared 4000 colon cancer patients with 3000 healthy controls and found that the more of these five lifestyle factors participants reported, the more likely they were to develop colon cancer. Furthermore, the relationships between the five lifestyle factors and colorectal cancer risk was independent of family history. Avoiding these five factors was also linked to fewer heart attacks and other diseases of inflammation.
The authors of a study that analyzed data from 13,600 screening colonoscopies in Saarland, Germany found that these same factors were strongly associated with increased risk of all stages of colorectal cancers (International Journal of Cancer, November 23, 2018). Another study showed that 992 people who were already diagnosed with colon cancer that had spread beyond the colon, who changed to a healthier diet and exercise program, had a 42 percent lower risk of dying over the next seven years compared to the control group who did not change their lifestyles (JAMA Oncol, April 12, 2018). The changes implemented in this study corrected each of the lifestyle factors listed above, as recommended by the American Cancer Society (ACS) Nutrition and Physical Activity Guidelines for Cancer Survivors.
How Lifestyle Factors May Cause Colon Cancer Your colon has more than 100 trillion bacteria in it, and what foods you eat and other lifestyle factors determine what types of bacteria grow there. Some types of bad bacteria increase colon cancer risk while other types of good bacteria help to decrease risk. 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). A 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, published online January 26, 2017). In another study, after just two weeks on a diet restricting red meat and adding lots of fruits, vegetables, beans and seeds, a group of 20 African-Americans had a significant reduction in specific colon bacteria and other risk factors for colon cancer (Nature Communications, April 28, 2015).
The Fusobacterium appear to increase colon cancer risk by suppressing a person's immunity that is supposed to kill cancer cells (World J Gastrointest Oncol, Mar 15, 2018;10(3):71–81). 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). Lack of fruits and vegetables increases colon cancer risk by the following mechanism: You cannot absorb soluble fiber and resistant starch from plants in your upper intestinal tract, so they pass to your colon where specific bacteria ferment them to generate short chain fatty acids (SCFA) that help you to avoid overweight and dampen down inflammation, which helps to protect you from colon cancer and other cancers (Proc Nutr Soc, 2015;74:23–36). A pro-inflammatory diet (high in foods that turn on your immune system and keep it overactive) increases risk for colon cancer (JAMA Oncol, Jan 18, 2018; Nutrients, Jul 30,2016;8(8):469; Arch Med Sci, 2010 Aug 30;6(4):605-10; Food Chem Toxicol, Feb 2012;50(2):95-103; Cancer Letters, 1992;65(3):227-232; Nutr Cancer, 2008;60:636-642; Mediators Inflamm, Oct 5, 2015; Annual Rev of Nutr, Aug 2017;37:293–320).
Avoid or Limit Mammal Meat and Processed Meats: A prospective study of 32,147 women followed for an average 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 meat with increased colon cancer risk (Colorectal Cancer, 2011 Rep Lond WCRF/AICR, 2011:1–40). A prospective 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). 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) has found that eating processed meat and red meat increases risk of colorectal cancer (J Gastroenterol, Dec 2, 2016; British Medical Bulletin, Dec 18 and 23, 2016; J Hum Nutr Diet, Jun 14, 2016), while vegetarians who eat fish have a 43 percent reduced risk for developing colon cancer, compared to people who eat meat (JAMA Internal Medicine, March 9, 2015).
Exercise and Avoid Being Overweight: A prospective study of 226,584 participants aged 45 years and over found that both being overweight and not having an exercise program are independent risk factors for colon cancer (BMC Public Health, March 6, 2018). Prolonged sitting time in this study was not a risk factor, but 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). Colon cancer is far more common in people who are overweight, which is also a major risk factor for having high blood sugar levels and diabetes. Overweight people have different types of bacteria in their colons than normal-weight people have (Nature, 2009;457:480–484). Normal-weight people with markers of high blood sugar are at more than double the risk of developing colon cancer (Cancer Epidemiology, Biomarkers & Prevention, Feb 2017). Eating sugar-added foods or red meat may increase colon cancer risk by leading to a fatty liver, which causes high blood sugar levels (J Hepatol, Mar 19, 2018).
Avoid High Rises in Blood Sugar after Meals: Cancer of the colon is associated with eating a lot of sugar and other refined carbohydrates found in sugared drinks, sugar-added foods, bakery products and so forth. 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 are constipating, which prolongs contact between food residue and the inner surface of the colon (Cancer Epidemiology Biomarkers & Prevention, 2001;10(7):725-731). Whole grains and other high-fiber foods may help to prevent colon cancer by sweeping stool and carcinogens through the colon at a faster rate.
Avoid Smoking and Alcohol: Smoking increases risk for developing and dying from 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 free radicals that can enter your bloodstream and enter every type of cell in your body to damage the DNA, which can cause cancers. Alcohol also is a potent carcinogen that can damage cellular DNA, and people who drink alcohol regularly are at increased risk for colon cancer (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 whole 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 and unnecessary drugs
At any age, you can reduce your risk for colon cancer and many other diseases by changing your lifestyle. Cancer survivors have been shown to live longer when they adopt a healthful lifestyle after their diagnosis and treatment, and many heart attack patients and diabetics can reverse much of the damage when they start to eat healthfully and get plenty of exercise.
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