The hottest area of medical research today may well be on the bacteria that live in your gut to affect how much you weigh, how long you live, and your susceptibility to many diseases. In the largest and most complete study of its kind ever, researchers analyzed genes of colon bacteria from 1,046 healthy Israelis and found that the bacterial composition of your colon is determined primarily by your lifestyle and what you eat, and has less than a two percent association with your genes (Nature, March 8, 2018;555:210–215).

Analyzing a person’s colon bacteria is far more dependable than analyzing a person’s genes for predicting their:
• weight
• fasting blood sugar
• ability to respond to insulin
• HDL cholesterol
• waist and hip circumference
• waist-hip ratio
• lactose level (the amount of dairy products person eats)

The authors also found that genetically unrelated people living in the same household tended to have the same bacteria in their colons, while a person’s relatives who did not live in the same household had totally different colon bacteria. This is an incredibly exciting study because motivated people can change their lifestyles but at this time scientists have no safe way to change a person’s genes.

Mediterranean Diet and Bacterial Endotoxins
Another recent study shows how the Mediterranean diet helps to prevent diseases and prolong life by changing the colon bacteria and reducing the harmful endotoxins produced when your body turns food into energy (Advances in Nutrition, May 15, 2018;9(3):193–206). Hundreds of studies show that an overactive immunity (inflammation) is a major cause of disease and premature death in North America today. Several recent papers suggest that certain bacteria in your colon can cause a two- to three-fold increase in blood levels of bacterial endotoxin that can cause inflammation. Diets high in sugar and saturated fat and low in fiber contribute to bacteria in your colon releasing bacterial toxins, and changes in your bile production that contribute to disease-causing inflammation. The Mediterranean diet is rich in unsaturated fats and fiber, and low in added sugars and saturated fats. An anti-inflammatory diet such as the Mediterranean diet also changes colon bacteria to reduce arterial stiffness, a significant risk factor for heart attacks (European Heart Journal, May 9, 2018).

Healthful and Harmful Colon Bacteria
Two to five pounds of bacteria, or about 40 trillion bacterial cells, live in your body (PLoS Biol, Aug 19, 2016;14(8):e1002533). Of the more than 1000 different types of bacteria that live in your colon, some are good for you while others can be harmful (Nature, 2014 Jan 23; 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, and heart attacks. 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. The damage caused by invading colon bacteria turns on your immunity to cause inflammation (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.

Gut Microbiome and Your Weight
Several studies show that obesity may be caused by unhealthful colon bacteria (Postgrad Med J, May 2016;92(1087):286-300). Studies in twins of which one is fat and the other is skinny show that transferring the colon bacteria from the fat twin to mice made mice fat, while the stool of the skinny twin did not fatten the mice (Science, 2013 Sep 6; 341(6150):10.1126). Overweight people may have colon bacteria that specifically help them to absorb more calories and form more fat in their bodies (Nature, 2006;444:1027–1031).

How to Grow a Healthful Microbiome
• Eat lots of fruits, vegetables, whole grains, beans, nuts and other seeds. They are high in fiber that fosters healthful colon bacteria (Food Funct, Apr 2016;7(4):1788-96).
• Eat whole grains that contain lots of fiber and beta-glucan (Br J Nutr, Jan 2008;99(1):110-20).
• Try a plant-based diet (Environ Microbiol Rep, Oct 2013;5(5):765-75).
• Restrict mammal meat (J Transl Med, Apr 8, 2017; 15: 73).
• Restrict refined carbohydrates (Diabetes Metab Syndr Obes, 2012;5:175-89).
• Restrict fried foods (Amer Journal Clin Nutr, Aug 2014;100(2):667–675).
• Avoid artificial sweeteners. Some artificial sweeteners appear to stimulate the growth of unhealthful colon bacteria (Gut Microbes, 2015; 6(2): 149–155).

How Fiber Promotes Good Gut Bacteria
How Gut Bacteria Affect Weight

Checked 4/20/23