Good bacteria that live in your gut can help to keep you healthy, while the bad colon bacteria increase your risk for heart attacks, strokes, diabetes, certain cancers and autoimmune diseases. Researchers have focused mainly on how diet affects the growth of good and bad gut bacteria, but now two new studies–one in humans and one in mice–show that exercise encourages the growth of good bacteria in your colon and reduces the number of bad ones. These studies suggest that exercise can do this without any changes in diet.
Exercise and Gut Bacteria in Humans
Researchers had 18 lean and 14 obese subjects exercise for 30 to 60 minutes, three days per week for six weeks (Medicine & Science in Sports & Exercise, Nov 11, 2017). Then they were told not to exercise for six weeks. All subjects were told not to change their diets. After the six weeks of exercise, all of the subjects, both obese and lean, had an increase in the good colon bacteria that make short chain fatty acids (butyrate) and suppress inflammation. The lean subjects had the greatest increase in the good bacteria after exercising and the obese subjects had a more modest increase in the good bacteria.
When the same subjects were checked after six weeks of not exercising, all had a marked drop in these good colon bacteria. This study shows that exercise appears to increase the number of good colon bacteria without any dietary change whatever, that lean people have a greater increase than obese people, and that the potential benefit does not last if exercise is stopped.
Exercise and Gut Bacteria in Mice
Researchers took fecal material from groups of exercising mice and sedentary mice, and transplanted it into the colons of the bacteria-free mice (Gut Microbes, published online Sep 1, 2017). The bacteria-free mice developed the same types of colon bacteria that they received from each donor group. Fecal samples taken from exercising mice gave the recipient mice much higher levels of the beneficial bacteria that produce high levels of short chain fatty acids (butyrate) that are anti-inflammatory and help to lower cholesterol.
Then the researchers gave the recipient mice chemicals that cause inflammation to damage their colons and cause colitis. The mice that had received bacteria from the exercising mice had far less inflammation, far less colon damage and much quicker recovery times than the mice who had received bacteria from the sedentary mice.
Functions of Gut Bacteria
More than 100 trillion microorganisms live in your colon (FEMS Microbiol. Rev, 2014;38:996–1047), which means that only about ten percent of the total number of cells in human body are human cells, with the rest coming from symbiotic bacterial cells (Nature, 2010 Jun 17; 465(7300):879-80). Over the last few years, a very large number of studies have increased our understanding of the many functions of gut bacteria. My reports on this important research include:
How Soluble Fiber Promotes Good Gut Bacteria
Gut Bacteria and Auto-Immune Diseases
How Gut Bacteria Affect Weight
Colon Cancer, Gut Bacteria and Diet
Anti-Inflammatory and Pro-Inflammatory Foods
Gut Bacteria to Help Treat and Prevent Cancers