Colon Cancer May Be Caused by Bacteria

More than 1.3 million North Americans have had colorectal cancer, a disease associated with lifestyle factors that encourage cancer-causing bacteria to thrive in your colon:

• eating lots of red and processed meats, sugar added foods, sugared drinks and fried foods

• not eating enough vegetables, fruits, nuts and whole grains

• not exercising

• being overweight

• smoking

• drinking alcohol

A new study shows 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 those who did not change their lifestyles (JAMA Oncol, April 12, 2018). The changes 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 Can Increase Colon Cancer Risk Your colon has more bacteria in it than you have cells in your body and certain bad bacteria increase colon cancer risk, while other good bacteria help to decrease risk. What you eat and other lifestyle factors determine which types of bacteria grow in your colon. 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, published online January 26, 2017).

These bacteria 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).

Lifestyle Factors to Reduce Risk for Colon Cancer Limit or Avoid 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 meats 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).

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).

Avoid High Rises in Blood Sugar after Meals: Normal-weight people with markers of high blood sugar or metabolic syndrome 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 causing a fatty liver that causes high blood sugar levels (J Hepatol, Mar 19, 2018). Markers of metabolic syndrome include systolic blood pressure over 120 at bedtime, triglycerides over 150, blood sugar over 140 one hour after eating, a good HDL cholesterol under 40, or being able to pinch more than two inches of fat under your skin near the belly button.

My Recommendations The same lifestyle factors that increase risk for colon cancer also increase risk for heart attacks, strokes, obesity, diabetes and certain other cancers, so making the recommended lifestyle changes will help to protect you from most of the major diseases that are associated with aging.

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