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The Fog in Your Head: The Cause Was in Your Gut, Not Your Brain | Brain Fog
Blog October 10, 2025

The Fog in Your Head: The Cause Was in Your Gut, Not Your Brain | Brain Fog

Dr. Yeonseung Choe
Dr. Yeonseung Choe
Chief Director

Brain Fog: The Root Cause Was in the Gut, Not the Brain

"It feels like my mind is foggy."

Today's Core Message: Unexplained brain fog, anxiety, and chronic fatigue may actually be signals of chronic inflammation originating from the 'gut,' not the brain. Let's embark on an exploration to uncover the true root cause.

Minor Work Mistakes and Anxiety: It All Started with That Day's Presentation

CASE STUDY

Mr. A, a developer in his late 30s, can't forget the day he messed up a crucial presentation. The information was clearly in his head, but the moment he looked at the screen, his vision blurred, and his mind went blank.

He never used to be like this, but lately, he's noticed a significant slowdown in his mental agility. Minor work errors have become frequent, and with each one, his anxiety—"What if I make another mistake?"—snowballs, like smoke from an unseen ember.

Mr. A thought all of this was due to excessive stress and anxiety. So, he tried meditation and consciously attempted to block out work thoughts after leaving the office. But the fog in his head rarely lifted. Instead, his self-reproach—"Am I mentally weaker these days?"—only deepened.

The clue he overlooked was in an unexpected place. It was the indigestion that habitually followed his dinners, which often consisted of late-night work and delivered food. He simply took antacids whenever he had indigestion and didn't think much of it.

The Breached 'Fortress Wall' and the 'Embers' Spreading Throughout the Body

What if Mr. A's foggy mind and frequent indigestion are, in fact, symptoms of a single underlying issue? What if anxiety isn't the cause of this issue, but merely another victim? To find the true culprit behind this phenomenon, we must turn our attention to the place farthest from the brain: the 'gut.'

The intestinal lining in our bodies is like a strong 'fortress wall' that protects us from harmful external substances. However, frequent stress, processed foods, and lack of sleep can cause cracks to form in this wall. This is called 'Leaky Gut.'

When the wall collapses, 'enemies' like undigested food particles or harmful bacteria unlawfully invade our bodies through the bloodstream. In traditional Korean medicine (TKM), these sticky internal waste products resulting from impaired digestive function are called 'Dam-eum (痰飮).' This 'Dam-eum' was believed to circulate through the blood, hindering the ascent of clear qi (淸陽) to the head and thus causing fog. This concept remarkably aligns with modern medicine's concept of neuroinflammation.

Our body's immune system sounds an alarm against these invaders, triggering an inflammatory response. This is the 'small spark that originated in the gut.' The problem is that these embers spread throughout the entire body via the bloodstream. And one of the places where these embers have the most detrimental effect is the 'brain.'

Brain Fog: Uncovering the True Culprit

The brain also has an ironclad 'border checkpoint' called the 'Blood-Brain Barrier (BBB),' which prevents just any substance from passing through.

However, chronic inflammatory signals originating from the gut gradually compromise the integrity of this border checkpoint. Consequently, inflammatory substances penetrate the checkpoint and invade the brain, causing 'neuroinflammation.'

This is precisely the moment when the gut-originated embers finally cause a dense fog to rise in the brain. 'Brain fog'—characterized by a dull mind, decreased concentration, and impaired memory—is essentially an emergency signal sent by brain cells that are unable to function properly due to neuroinflammation.

In fact, in the case of a patient experiencing similar symptoms to Mr. A, high levels were found for dairy and gluten in an IgG Food Intolerance Test. After eliminating these foods, not only did their indigestion improve, but their brain fog also showed a remarkable pattern of improvement.

Ultimately, the problem plaguing Mr. A was not one of 'willpower' or 'mental strength.' It was a systemic issue where a compromised 'fortress wall (barrier)' was not repaired in time, allowing the 'smoke' of inflammation to spread throughout the body and paralyze the functions of the most crucial 'command center (brain).'

Could the 'brain fog' you're experiencing perhaps have originated from a slice of bread you ate yesterday, or a glass of milk you drank late last night?

Extinguishing the 'embers' in the gut and finding clues to repair the 'fortress wall' could very well be the greatest first step in navigating through the fog.

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Dr. Yeonseung Choe

Dr. Yeonseung Choe Chief Director

I have met many patients who came after visiting multiple medical institutions and departments for persistent or recurrent conditions. Symptoms normally handled by different specialties—such as abdominal pain, headaches, palpitations, dizziness, and insomnia—may overlap in one person. Sometimes there is no clear improvement despite taking medication for each symptom, and being unwell gradually becomes part of daily life. In these cases, I look beyond individual diagnoses and examine how the symptoms connect and change together. Asking only about the most uncomfortable symptom today does not reveal the full course. I look at when the body first began to change and what happened after illness, surgery, childbirth, or starting and stopping medication. I also review changes in weight, diet, and sleep, then trace which symptoms improved with previous treatment and which remained. Test results, diagnoses, and the course of previous treatment are important for understanding the current condition. Clinical research in modern Korean medicine, physiological and pathological research in modern medicine, and observations recorded in classical Korean medicine texts offer different perspectives on the same body. Rather than fitting a patient into one perspective, I consider what each can and cannot explain and look for clues that connect symptoms and treatment histories that were previously considered separately.

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