Hundreds of studies done in the last 15 years have shown how your microbiome (gut bacteria) helps you to retain your health (Aliment Pharmacol Ther, 2019;49(5):506-515), and that what you eat determines the ratio of healthful to harmful types of bacteria in your colon. These bacteria govern your immune system that determines, to a large degree, what diseases you will develop and how long you will live. Your colon bacteria appear to determine your chances of suffering from obesity, diabetes, heart attacks, strokes, cancers and many other diseases.
Your colon contains trillions of bacteria that help to control your digestion and just about everything that happens in your body. What you eat determines the types of bacteria that thrive in your gut. Fiber in plants promotes the growth of the healthful bacteria, so when you eat lots of plants, you will build a large colony of these bacteria. The healthful bacteria convert the soluble and fermentable types of fiber into short chain fatty acids (SCFAs) that have immense health benefits (J Lipid Res, Sept 2013;54(9):2325-40). SCFAs can help to:
• reduce inflammation
• lower high levels of blood sugar, cholesterol and blood pressure
• reduce hunger
• cause your intestinal linings to produce beneficial mucus that lines your colon to help prevent the harmful bacteria from penetrating there
How Much Fiber Do You Need?
Eating a lot of the foods that contain soluble fiber helps the good bacteria to overgrow the bad ones by depriving them of oxygen (Science, Aug 11, 2017:357(6351):548-549). Soluble fiber is found in varying amounts in vegetables, fruits, beans, whole grains, nuts and other edible seeds. The more of these foods you eat, the higher your levels of SCFAs (Gut, Nov 2016;65(11):1812-1821). Insoluble fiber is usually not broken down in the colon, so it passes through your digestive tract intact and helps to move undigested food through your colon to help prevent and treat constipation. See Soluble and Insoluble Fiber
Less than five percent of North Americans meet the Institute of Medicine’s recommended fiber intake of 25 grams for women and 38 grams for men. The average person gets only 16 grams of fiber per day. A review of 185 prospective studies and 58 clinical trials shows that people who take in the most fiber had a 15–30 percent decrease in deaths during the study periods, reduced rates of heart attacks, strokes, diabetes, and colorectal cancer, as well as less high blood pressure, high cholesterol or obesity (Lancet, Feb 2, 2019;393(10170):434-445). The hunter-gatherer Hadza tribes in Tanzania take in up to 150 grams per day of fiber, which is more than ten times what North Americans eat, and suffer no apparent ill effects (PLoS Biology, 2018; 16(11):e2005396).
Lifestyle Changes Can Improve the Bacteria in Your Colon
Your current diet determines which bacteria live in your gut. Even if your colon is full of harmful bacteria, you can change your colon bacteria by switching to a high-fiber diet that includes a wide variety of plants.
Older people who live in long-term-care facilities and eat a very low-fiber diet lack healthful diversity and growth of the bacteria in their colons and have very high markers of inflammation and frailty (Nature, 2012;488:178–184).
Another study followed a large number of people who moved from Thailand, where they ate lots of plants, to Minnesota where they switched to the typical Western Diet of fast food, sugared drinks and foods, meat, and fried foods. Within just a few weeks they lost their advantage of diverse and healthful colon bacteria (Cell, Nov 1, 2018;175(4):962-972.e10).
Giving high doses of antibiotics commonly used to treat hospitalized patients with very serious infections did not kill all of their gut bacteria, but caused an immediate drop in healthful bacterial colon diversity. Clostridium species that had not been found before the patients received antibiotics appeared in large amounts. Clostridia overgrowth is responsible for many difficult-to-treat infections that can follow the use of antibiotics (Nat Microbiol, Nov 2018;3(11):1255-1265).
• Don’t fall for the latest “superfood” gimmick — just work on taking in plenty of fiber. Regardless what else you eat, try to eat lots of vegetables, beans, fruits, unground whole grains, nuts and other seeds — all rich sources of fiber, which helps to promote healthful gut bacteria.
• Daily exercise also encourages the growth of your colony of healthful bacteria.
• Restrict mammal meat, fried foods, foods with added sugar and all drinks with sugar in them, as these foods foster the growth of harmful bacteria in your colon.