Your Body Keeps the Score — The Gut-Brain Connection Nobody Told You About

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Your Body Keeps the Score — The Gut-Brain Connection Nobody Told You About<br>The Examined Life · Issue #2

maheen ahmed<br>May 30, 2026

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Last issue we talked about why you can’t stop scrolling. This week we go somewhere most people have never been taken — inside your own body. What you’re about to read will change how you understand your mood, your anxiety, and your mind. Permanently.

Here is a number that should stop you in your tracks.<br>95.<br>That is the percentage of your body’s serotonin that is produced not in your brain — but in your gut.<br>Read that again.<br>The chemical most associated with happiness, emotional stability, and mental wellbeing. The chemical that antidepressants like Prozac are designed to regulate. The chemical your doctor is thinking about when you describe feeling low, anxious, or hollow.<br>Ninety-five percent of it lives in your intestines.<br>Not your head. Your gut.<br>If that surprises you — if nobody ever mentioned this in any conversation about your mental health — you are not alone. The science has been sitting in peer-reviewed journals for decades. And yet the idea that your stomach might be the organ most responsible for how you feel on any given Tuesday remains almost entirely absent from mainstream conversations about mental wellbeing.<br>That ends today.

The second brain you didn’t know you had

The digestive system — far more than a food processor. It is a neurological command centre.

Your gut contains approximately 500 million neurons.<br>To put that in perspective: your spinal cord contains around 100 million. The network of nerve cells lining your gastrointestinal tract — from your oesophagus all the way to your colon — is so vast, so complex, and so functionally independent that neuroscientists have given it its own name: the enteric nervous system. Informally, they call it the second brain.<br>This is not a metaphor. The enteric nervous system can sense, process, and respond to information entirely on its own, without any instruction from the brain in your skull. It has its own reflexes. Its own memory, in a functional sense. Cut the vagus nerve — the primary communication highway between gut and brain — and your digestive system keeps working.<br>Your gut does not need your brain to function. In evolutionary terms, the enteric nervous system is ancient — far older than the cerebral cortex. Some researchers believe the brain we think with may have evolved from the gut nervous system, not the other way around.<br>Let that sit for a moment.

The vagus nerve: your body’s secret broadband cable

The vagus nerve — the body’s most important communication highway, running from brainstem to gut.

The vagus nerve is the longest cranial nerve in the human body. It runs from your brainstem down through your neck, your heart, your lungs, and deep into your abdomen, connecting your central nervous system to almost every major organ along the way.<br>For a long time, scientists assumed it was a one-way street — the brain sending instructions downward to the body. Then researchers started measuring traffic on the line.<br>What they found was extraordinary.<br>Approximately 80 to 90 percent of the signals travelling along the vagus nerve are going upward — from the gut to the brain. Not the other way around.<br>Your gut is not waiting for orders. It is constantly, silently, sending a stream of information directly into the decision-making and emotional centres of your brain. Every meal, every moment of stress, every shift in your microbiome — your gut is reporting up.<br>This has enormous implications for how we think about anxiety, depression, and mood. Because if the gut is the dominant communicator in this relationship, then the state of your gut — its microbial health, its inflammation levels, its chemical output — is shaping how your brain feels in ways that no amount of positive thinking or cognitive reframing can fully override.<br>You cannot think your way out of a sick gut.

The microbiome: 38 trillion silent tenants

Your body contains approximately 37 trillion human cells.<br>It also contains approximately 38 trillion microbial cells — bacteria, fungi, viruses, and other microorganisms living primarily in your gut. You are, technically, slightly more microbial than human by cell count.<br>This community of organisms — your microbiome — is not merely a passive passenger. It is an active, metabolically complex ecosystem that produces neurotransmitters, regulates inflammation, trains your immune system, and communicates directly with your brain via the vagus nerve and the bloodstream.<br>Your gut bacteria produce:<br>GABA — the primary inhibitory neurotransmitter in your brain, directly associated with calm and the reduction of anxiety

Dopamine precursors — the raw material your brain uses to manufacture the motivation and reward chemical we discussed in Issue #1

Short-chain fatty acids — which cross the...