What do the voices in your head say?

It’s a fascinating phenomenon with potential for both wonderful as well as tragic issues in human life: the power of the intestinal microbiome to influence your internal dialogue.

We all have a constant conversation going on with ourselves. Anyone who has tried to meditate and stop the internal dialogue in your head knows how difficult it can be to “turn off” this dialogue.

The content and mood of this internal dialogue can differ wildly from moment to moment. It could be a dialogue of happiness and optimism, or it could be a dialogue of criticism and hatred. It could be a dialogue of love and affection, or it could be a dialogue of anger and resentment. Obviously, personality traits, active circumstances (e.g., are you in traffic, in a business meeting, at a movie with a love story), interactions with other people and other factors all impact your internal dialogue. But the content and mood of your internal dialogue is, to a surprising degree, subject to the influence of microbes via the metabolites they produce, examples of the so-called “gut-brain axis” and of “psychobiotics.”

To illustrate, witness:

• When you restore the microbe lost by nearly all Americans, Lactobacillus reuteri, and thereby boost oxytocin, you experience an increase in love and empathy for other people, as well as reduced social anxiety, i.e., anxiety commonly experienced in social settings such as an office party or neighborhood get-together. Many also experience an increase in libido and in the erotic content of dreams. But you can also experience an “us versus them” mentality, i.e., a sense of belonging to a group but consider others as “outsiders,” as well as schadenfreude, i.e., gloating over someone else’s misfortune.
• Serotonin levels are lower in people experiencing depression, with 90% of all serotonin originating from the gastrointestinal (GI) tract. Turicibacter sanguinis is the main microbe that drives serotonin production by intestinal cells.
• The unhealthy species of small intestinal bacterial overgrowth, SIBO, such as E. coli, Klebsiella, and Pseudomonas, all have something called lipopolysaccharide (LPS) in their cell walls that is released into the intestines upon microbial death. In SIBO, a situation in which all 30-feet of GI tract are inhabited by these and other species, means that there is a flood of LPS, some of which enters the bloodstream, a process called endotoxemia in which high levels of LPS can be measured in the bloodstream. (There is greater entry of LPS in SIBO compared to dysbiosis confined to the colon, since the 24-feet of small intestine has a thin single-layer protective mucus barrier, compared to the thicker two-layer mucus barrier of the colon.) A German research group conducted two clinical studies in which they injected LPS (very dangerous: a small miscalculation in dose and you can kill somebody by injecting LPS) into the bloodstream of non-depressed volunteers. LPS injection provoked all the symptoms of depression after several hours, with brain MRI showing all the hallmarks of depression. In other words, bacterial LPS from intestinal microbes caused an internal dialogue of hopelessness, disinterest, and low self esteem.
• There is some clinical evidence that people with treatment-resistant depression with higher levels of inflammation respond to antibiotics. (Although not formally explored yet, you can predict that treatment-resistant depression with inflammation is almost certain to represent SIBO with endotoxemia.)
• When you embark on an effort to kill off bacteria in SIBO or of fungi in fungal overgrowth, the Jarisch-Herxheimer, or “die-off,” reaction that ensues due to the release of a flood of bacterial or fungal breakdown products is commonly associated by anxiety, panic attacks, depression, suicidal thoughts, and nightmares.

That’s just a sample. But you can appreciate that much of the internal dialogue we conduct in our heads reflects what the microbes in our GI tracts are doing.

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