A six-week program of exercise markedly increased the types of healthful colon bacteria and their functions in healthy but previously sedentary people (Med Sci Sports Exerc, Apr 2018;50(4):747-757). The 18 lean and 14 obese study participants followed a supervised program of treadmill running or cycling at increasing intensity from moderate to vigorous, in 30-60 minute sessions three times a week. They then returned to their sedentary habits and were checked again after an additional six weeks.
At the end of the six-week exercise program, the lean group had more of the healthful types of colon bacteria that ferment unabsorbed soluble fiber into short chain fatty acids (SCFAs). The gut bacteria changes in the obese group were not as pronounced. SCFAs reduce:
• harmful inflammation,
• high cholesterol,
• high blood pressure, and
• excess body fat.
The participants also markedly increased their fitness level as measured by their VO2max (maximal ability to take in and use oxygen), increased their muscle size and reduced their body fat. However, the exercise-induced beneficial changes in their colon bacteria were lost soon after they had stopped exercising.
Differences Between Healthful and Harmful Colon Bacteria
The healthful bacteria in your colon are perfectly happy to eat the same foods that you do, so they stay within the colon and do not try to invade the cells lining it. The harmful types of bacteria try to penetrate the cells lining your colon and your body responds by turning on your immunity to its full ability to fight the invading bacteria. This is called inflammation. After your immunity kills invading germs, it is supposed to shut down. However, with the constant invasion of your colon cells by harmful bacteria, your immunity continues to stay active, using the same cells and cytokines that kill germs to attack your own body. This inflammation causes or worsens virtually all of the common intestinal disorders: ulcerative colitis, Crohn’s disease, irritable bowel syndrome, colon cancer and so forth. The same inflammation can damage DNA to increase your risk for cancers, punch holes in your arteries to start plaques forming there, and even cause heart attacks by breaking off the plaques.
Lifestyle Factors that Encourage the Growth of Healthful Bacteria
• Exercise: This new study and many others suggest that exercise is a healthful way to increase the colony of good bacteria in your colon. Another study showed that competitive athletes had much healthier ratios of the healthful to harmful colon bacteria than non-athletes (Gut, April 2018;67(4):625-633). Animal studies show that exercising improves the composition of healthful bacteria in your gut to reduce excess body fat (PloS one, 2014;9(3):e92193), improve immunity (Environmental Health Perspectives, 2013;121(6):725-30), reduce inflammation (Metabolism: Clinical and Experimental, 2012;61(8):1058-66), improve insulin sensitivity (Frontiers in Endocrinology, 2014;5:137), and improve mental function (Cell, 2014;156(1-2):84-96). Exercise decreased the ratio of the harmful firmicutes to the healthful bacteroidetes in the colons of male mice to prevent diet-induced body fat increase and bone loss (PLoS ONE, 2015;10(5):e0125889; Bone, March 28, 2018).
• Diet: A high-fiber diet, full of vegetables, fruit, legumes, whole grains and nuts, increases growth of healthful colon bacteria (Gut, 2014;63(12):1913-1920). Bacteroidetes are examples of healthful bacteria and Firmucutes are harmful bacteria. A high ratio of Firmicutes to Bacteroidetes is associated with obesity, type II diabetes, and high blood sugar (Beneficial Microbes, 2014;5(1):33-43). Several studies show that healthful colon bacteria can lower high blood sugar levels that help both to treat and to prevent diabetes (Diabetologia, Jun 2017;60(6):943-951). You also encourage the growth of healthful bacteria by maintaining a healthful weight.
Checked 2/17/23
