How Good Gut Bacteria Improves Health


Eagle, CO

Last updated on Sep 30, 2021

Posted on Sep 30, 2021

Health column by Dr. Greg Feinsinger. Champion of Whole Food Plant Based Living and righteous person.

This is the second column in a series based on information from “Fiber Fueled,” by gastroenterologist Will Bulsiewicz, M.D. “Eat to Beat Disease,” by William Li, M.D., was also used for this column because it includes a particularly good description of the gut microbiome.

Last week’s column was about how the trillions of bacteria that make up the human gut microbiome can affect many aspects of human health. Some readers may find it hard to believe that these bacteria play a role not only gastrointestinal health, but also conditions as disparate as obesity, immune disorders, hormone problems, cardiovascular disease, mental health, diabetes, and cancer.

To understand the gut microbiome it’s first important to know that certain good gut bacteria make three short-chain fatty acids (SCFAs) that are critical for good health:  propionate, butyrate, and acetate. Propionate lowers cholesterol, reduces inflammation, prevents atherosclerotic plaque in arteries, improves digestive health, and activates immune cells. Butyrate is the main form of energy for the cells that line our colons, has anti-inflammatory effects, stimulates angiogenesis (formation of new blood vessels) needed for wound healing, and guides stem cells to morph into different types of organs. Acetate stimulates leptin, which suppresses hunger.

Other gut bacteria do the following (the list could go on for pages, and it gets longer with more research, but this will give you an idea):

  • Certain Lactobacillus species promote intestinal healing, by reducing inflammation.
  • Other gut bacteria suppress abnormal cells that cause breast cancer.
  • Lignans in certain plants are metabolized by gut bacteria to bioactive compounds that suppress breast cancer.
  • Other metabolites produced by gut bacteria reduce stress and anxiety.
  • Indolepropionic acid is a metabolite produced by gut bacteria that protects against type 2 diabetes.
  • The layer of cells that lines the gastrointestinal system is covered by a layer of mucus, and the health of both depends on good bacteria.
  • Certain good gut microbes secrete an enzyme that activates estrogen so it can do its job.
  • A variety of Clostridium bacteria convert glucocorticoids like cortisol into androgens.
  • Ninety percent of the serotonin and 50 percent of norepinephrine—both “happiness neurotransmitters”—are produced in the gut by good bacteria.

Fecal transplant—introducing stool from a healthy person into a sick person, via a tube, capsules, or enema—is illustrative of the healing power of a healthy gut microbiome. Following are two examples:  1) Clostridium difficile (C. diff) is a normal inhabitant of the human gut. In certain situations such as use of antibiotics, it can take over the microbiome and cause severe illness and even death. In the past, a specific antibiotic was used to treat it, but C. diff became resistant. Fortunately, fecal transplant from a normal person normalizes the microbiome of the affected person, and the illness resolves. 2) Central obesity (extra weight around the middle) is common today, and causes insulin resistance, where tissues can’t use insulin like they should. Insulin resistance leads to type 2 diabetes and heart disease. When overweight adult men with insulin resistance received a fecal transplant from a lean person, insulin sensitivity improved.

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