The hottest area of research in medicine today is about the bacteria in your colon called the microbiome. More and more studies show that exercise, in addition to a healthful diet, helps to increase the numbers of healthful bacteria in your colon that may prevent or treat obesity, diabetes, heart attacks, inflammation and even certain cancers (Ex and Sport Sci Rev, April 2019;47(2):75-85).

More than 100 trillion microorganisms live in your body (FEMS Microbiol Rev, 2014;38:996-1047) and weigh two to five pounds (PLoS Biol, Aug 19, 2016;14(8):e1002533). Of the more than 1000 different types of bacteria that live in your colon, some are healthful while others can be harmful (Nature, Jan 23, 2014;505(7484):559–563). The healthful bacteria are content to eat what you eat as food passes through your intestines, so they stay in your colon and do not try to cross into your cells and bloodstream. Healthful colon bacteria can form metabolites that help to prevent obesity, diabetes, heart attacks and even depression. On the other hand, the harmful bacteria are not happy with your food supply so they try to find food somewhere else by invading the cells lining your colon. Your immune system responds by producing proteins and cells that attack and try to kill the invading bacteria. If the invading bacteria continue to try to penetrate your cells day after day, your immune system stays active all the time. This is called inflammation. The same antibodies and cells that are supposed to kill invading germs can attack and damage your arteries to cause plaques to form, and can damage your DNA to cause cancer (PLoS One, Apr 13, 2017:12(4):e0176062). The harmful bacteria can also convert nutrients in your colon to other chemicals that can be harmful and cause diseases.

Exercise Can Increase Good Bacteria in Your Colon
In 2016, researchers showed that exercise increases the number of healthful gut bacteria in mice and decreases the numbers of harmful ones (PLoS One, Mar 8, 2016;11(3):e0150502.) A later study showed that just six weeks of exercise markedly increased levels of healthful gut bacteria in humans, and after the study subjects stopped exercising, the levels of healthful gut bacteria dropped to their previous lower levels (Med Sci Sports Exerc, Apr 2018;50(4):747-757).

There are many theories on how healthful gut bacteria dampen inflammation to help prevent disease (Gut Microbes, Mar 4, 2018;9(2):115-130). Healthful intestinal bacteria:
• convert soluble fiber in your colon into short chain fatty acids (SCFAs) that dampen inflammation, lower high cholesterol and blood pressure, and help you lose excess weight (Diet Microbiome Health, 2018:299–345).
• markedly reduce pro-inflammatory cell-signaling proteins and increase anti-inflammatory ones, as well as antioxidant enzymes (Exercise and Sport Sciences Reviews, April 2019;47(2):75-85)
• lower high blood sugar to help prevent diabetes (Annual Rev Med, (2011) 62:361–80)
• increase mucus production to help protect the colon linings from harmful bacteria
• increase intestinal motility (J Neurogastroenterol Motil, 2012; 18(1):64–9) and push gas through (Am J Med, 2004; 116(8):536–9) to move food faster through the intestines and help to prevent constipation
• increase the circulation of bile acids from the liver; accumulation of bile acids increases inflammation (J Hepatol, 2013; 58(5):949–55).

My Recommendations
You can help to prevent heart attacks and certain cancers by adopting a lifestyle that promotes the growth of healthful bacteria in your colon and reduces inflammation:
• Try to exercise every day
• Eat a plant-based diet with lots of vegetables, fruits, whole grains, beans, nuts and other seeds
• Restrict pro-inflammatory foods, such mammal meat, processed meats, fried foods, and drinks with sugar in them
• Avoid being overweight
• Avoid smoke and alcohol