The largest prospective study yet of 121,111 adult health professionals in the Nurses’ Health and Health Professionals Follow-Up Studies found 2733 cases of colon-rectal cancer, with 901 deaths. Sugar-sweetened beverages were associated with significantly increased risk for suffering and dying from colon cancer (Am J Clin Nutr, Apr 25, 2022). Another study of 96,000 participants reported that women who drank more than two sugar-sweetened beverages a day suffered more than double the risk of developing colorectal cancer, compared with women who drank less than one sugary drink a week (Gut, May 6, 2021). Since the 1990s, the incidence and death rate of colorectal cancer has been rising steadily among adults younger than 50 (National Cancer Institute News, Nov 5, 2020).

How Sugared Drinks Can Harm Your Colon
More than 100 trillion bacteria live in your colon, and these bacteria help to govern your immune system. Good and bad bacteria compete for space in your colon. The healthful bacteria are happy eating the food that reaches them in your colon, while the harmful bacteria are not happy with the food that you eat and instead try to invade the cells lining your colon. Your immune system tries to defend you by producing huge amounts of white blood cells and chemicals that work to destroy the invading bacteria. The damage caused by invading colon bacteria turns on your immune system to cause inflammation (PLoS One, Apr 13, 2017:12(4):e0176062).

One study in mice found that diets high in sugar caused severe colitis by increasing harmful colon bacteria and decreasing healthful colon bacteria (Sci Transl Med, Oct 28, 2020;12(567):eaay6218). Feeding mice a high-sugar diet for just seven days destroyed their gut’s protective mucus layer to increase risk for persistent diarrhea, abdominal pain, and rectal bleeding. Furthermore, feeding feces from the sugar-treated mice to mice that had not received the sugar diet, caused the same gut changes. This suggests that the intestinal damage was caused primarily by the increased growth of harmful bacteria caused by the high-sugar diet. Harmful bacteria produce enzymes that break down the mucus that lines and protects your colon from invasion by other bacteria, while the healthful bacteria markedly increase this mucus protective layer.

Sugar in foods and drinks is supposed to be absorbed in the upper intestinal tract, but taking in large amounts of sugar can cause some of the sugar to pass through the intestines unabsorbed. This sugar arrives in your colon where it can harm you by keeping healthful bacteria from growing in your colon and encouraging the overgrowth of harmful bacteria (PNAS, Dec 17, 2018). See Eating Lots of Sugar May Damage Your Colon

My Recommendations
I recommend limiting all sources of added sugars in your diet, particularly all drinks with sugar in them. Added sugars go by many names; see my report on Hidden Sugars. Read the list of ingredients on any new food you buy and realize that you are getting sugar if you see any of these terms: anhydrous dextrose, brown sugar, cane juice, confectioner’s powdered sugar, corn syrup, corn syrup solids, crystal dextrose, dextrose, evaporated corn sweetener, fructose, fruit nectar, galactose, high-fructose corn syrup (HFCS), glucose, honey, invert sugar, lactose, malt syrup, maltose, maple syrup, molasses, nectars, pancake syrup, raw sugar, sugar cane juice, sucrose, and so forth. Sugars extracted from fruits (such as grapes or apples) are no more healthful than any other source of sugar.

In addition to limiting sugar intake, you can reduce your risk for colon cancer by:
• avoiding red meat (meat from mammals), processed meats, and fried foods
• avoiding smoke and alcohol
• maintaining a healthful weight
• exercising regularly

See: Gut Bacteria and Colon Cancer Risk Factors
Eating Fermented Foods Can Improve Colon Bacteria