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by
Emeran Mayer
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December 23 - December 30, 2021
The intensity of this experience engraved itself into the deepest layers of my emotional memory—a permanent reminder of just how powerful gut sensations (and their memories) can be.
In your intestine, the toxin binds to receptors located on the serotonin-containing cells. This signal immediately switches your GI tract’s setting to “horrific vomiting and hurricane-like diarrhea.”
This is an inbuilt survival mechanism: when your gut detects enough of a toxin or pathogen, your enteric nervous system issues an evacuation order to your entire GI tract aimed at expelling the toxin from both ends of your digestive tract—a smart reaction, if not a pretty one.
The reaction is driven by serotonin-containing cells in the upper gut, which are particularly important in the generation of gut sensations.
Just like the other hormones contained in the endocrine cells of the gut, the released serotonin activates sensory nerve endings in the vagus nerve and the enteric nervous system (ENS), which in turn keep the ENS informed about what is moving down the intestinal tract, enabling it to trigger the all-important peristaltic reflex.
Serotonin is the ultimate gut-brain signaling molecule.
Serotonin-containing cells are intricately connected to both our little brain in the gut and to our big brain.
serotonin-containing nerves in the gut play a key role in regulating the peristaltic reflex,
Given the gut’s enormous serotonin stores, located close to vagal nerve pathways that link directly to the brain’s affective control centers, it’s certainly conceivable that a constant stream of low-level, serotonin-related gut signals are being sent to our brain’s emotional centers, in response to intestinal contents rubbing against the serotonin-packed cells, or in response to gut microbial metabolites.
Food as Information
when it comes to collecting, storing, analyzing, and responding to massive amounts of information, the gut-brain axis is a true supercomputer—a far cry from the plodding digestive steam engine it was once thought to be.
the gut microbes play a prominent role in this connection between what we eat, and how we feel.
The vast majority of gut microbes are not only harmless, but are in fact beneficial for our health and well-being; these are referred to by scientists as symbionts or commensals.
vagal inflammation, the sensitivity of vagal nerve terminals to satiety signals decreases, compromising the normal mechanism that stops you from eating after a full meal.
cytokines may spill into the bloodstream, travel to the brain like a hormone, transverse the blood-brain barrier, and activate immune cells—called microglial cells—inside the brain.
Some of these metabolites can increase the production of serotonin in enterochromaffin cells, making more of this molecule available for signaling to the brain via the vagus nerve. They can also alter your sleep, pain sensitivity, and overall well-being.
play a role in how good you feel after a healthy meal rich in fruits, whole grains, and vegetables, or how bad you feel after eating too many greasy potato chips or a basket of deep-fried chicken.
when stress or high anxiety causes the brain’s emotional operating programs to create dramatic plots that play out in our guts, it alters gut contractions, rates of transit from the stomach to the large intestine, and blood flow. This can dramatically alter living conditions for microbes in the small and large intestine, and is probably one of the reasons why the composition of your gut microbes is altered during stress.
brain-gut-microbiome axis.
If it’s important, humans listen to their gut.
Gut feelings and intuitions can be viewed as opposite sides of the same coin. Intuition is your capacity for quick and ready insight.
Gut feelings reflect an extensive and often deeply personal body of wisdom that we have access to, and that we trust more than the advice provided by family members, highly paid advisors, and self-declared experts or social media.
book, How Do You Feel? An Interoceptive Moment with Your Neurobiological Self,
Feelings (including gut feelings) are sensory signals that tap into your brain’s so-called salience system.
Salience is the level to which something in the environment can catch and retain one’s attention, because it is important or noticeable; something that stands out.
signals, are encoded by a vast array of receptors in the gut wall and sent to the brain via nerve pathways (in particular the vagus nerve) and via the bloodstream.
Even though they originate in the gut, gut feelings are created from the integration of many other influences, including memory, attention, and affect.
insular cortex, which is the central hub of the brain’s salience network.
better you are at tracking your own heartbeats, the better you are at experiencing the full gamut of human emotions and gut feelings.
The more viscerally aware, the more emotionally attuned you are.
lactobacillus that makes a metabolite of GABA—a substance that acts on the same brain receptors as the anxiety-reducing drug Valium.
a leading expert on the VENs, says that when you meet someone, you create a mental model of how that person thinks and feels. You
These areas are also active when you experience pain, fear, nausea, or many social emotions.
Humor serves to resolve uncertainty, relieve tension, engender trust, and promote social bonds.
During REM sleep, your breathing becomes more rapid, irregular, and shallow, your eyes jerk rapidly in various directions, and your brain becomes extremely active.
while our body movements are turned off, the brain-gut-microbiota axis is more active during sleep than at any other time.
Why is dreaming significant? One proposed theory is that dreaming during REM sleep helps to integrate and consolidate various aspects of our emotional memories.
analytical psychology, an elaborate conceptualization of psychology that includes such key concepts as a shared (collective) unconscious; universal, inborn patterns of unconscious images (so-called archetypes) that guide our behavior; and the concept of individuation, a psychological process of integrating opposite psychological tendencies, like introversion and extroversion.
dream analysis as the key strategy to get access to our unconscious.
Ericksonian hypnosis is one. Milton Erickson, a famous hypnotherapist, was a master at putting his patients into a trance by directing his elaborate, hypnosis-inducing stories alternatively to the conscious, rational (left) side of the brain and to the wise, all-knowing unconscious (right) side of the brain.
They may view themselves as always having had a “sensitive stomach”
THE ROLE OF FOOD: LESSONS FROM HUNTER-GATHERERS
Millions of years of evolution have perfected the gut to sense, recognize, and encode everything we eat and drink into patterns of hormones and nerve impulses sent to regulatory centers in the brain.
also learned about one unique aspect of the Yanomami’s eating habits: the complete lack of salt as a food additive.
Decreased biodiversity affects the marine life living on the coral reefs, and the honeybees and monarch butterflies in North America.
first two and a half to three years shape our gut microbiome for a lifetime.
Harvard University studied the acute effect of switching healthy individuals from their normal diet to either a plant-based diet (rich in grains, legumes, fruits, and vegetables) or an extreme animal-based, high-fat diet (composed of meats, eggs, and cheeses). The short-term switching of individuals from their regular diet to either a plant- or an animal-based diet also changed their gut microbial composition.
The diet you choose determines not only the tunes it plays, but also the quality of these tunes. And you, ultimately, are the conductor of the symphony. CHAPTER
Many of us can relate to a scenario like this—on a day when we’re feeling particularly stressed or anxious, we reach for foods—donuts, bagels, muffins, candy—that make us feel a little better. Our emotional states are closely related to our fat and sugar intake, and many of us aren’t paying enough attention to what we’re eating.
belly (so called visceral fat), were the primary source of inflammatory molecules, called cytokines or adipokines, that circulate in the blood, reaching the heart, the liver, and the brain.
