⏱ 6-minute read

I want to share something personal with you. Something I wish I knew years ago and that I believe is an important piece of health information that needs to be shared.

There was a season in my life when I was struggling with depression. Real, exhausting, heavy, hard-to-get-out-of-bed depression. Every day was a struggle, and it was hard trying to ‘push through’. As a nurse I understood the clinical picture, and it made sense at the time when my doctor suggested an antidepressant. I understood the reasoning — serotonin is low, this medication raises it, you will feel better.

While I did take an antidepressant for a short period, it really only helped a little, but also made me feel even sleepier than I already was, so I decided an antidepressant was not the right choice for me.

Before we go further, I want to be clear about something. This newsletter is not here to dismiss or discredit antidepressants. For many people, antidepressants have been a lifeline during some of the darkest and most overwhelming seasons of their lives. The information I share here is not a replacement for that. It is an invitation to understand what may be happening at a deeper level in your body so that you can have more informed, empowered conversations with your doctor about your own health journey. If you are currently taking an antidepressant, please know this — never stop it abruptly. Discontinuing antidepressants without medical guidance can cause serious withdrawal effects and should always be done slowly and under the direct supervision of your prescribing physician. My goal is simply to pull back the curtain on the underlying biology so that whatever path you are on, you are walking it with more knowledge than you had before.

What I know now — after studying the gut-brain axis, the enteric nervous system, and the microbiome — is that the conversation I was having with my doctor was happening in entirely the wrong location.

Because serotonin is not primarily a brain issue.

It is a gut issue.

And understanding that has changed everything about how I approach mental wellness — for myself and for every person I work with.

Before We Go Further — A Quick Connection to Last Issue

If you read last week's newsletter on the enteric nervous system — your second brain — you already know that your gut contains over 500 million neurons organized into two sophisticated neural networks embedded in the gut wall. You know that those networks govern digestion, immune function, and the bidirectional communication with your brain through the vagus nerve. If you have not had a change to read it, you can find it here:

Today we are going one layer deeper into that system — specifically into a group of specialized cells that live within the gut lining called enterochromaffin cells. If the enteric nervous system is the second brain, enterochromaffin cells are among its most important workers. And what they do is directly connected to your mood, your emotional resilience, your sleep, and your mental health in a way that most people — and most doctors — have never been taught.

Scattered throughout the lining of your gastrointestinal tract — from the stomach through the small and large intestine — are specialized sensory cells called enterochromaffin cells (EC cells). They make up only a small fraction of the cells in your gut lining, but their contribution to your health is wildly disproportionate to their size.

EC cells are the primary producers of serotonin in the human body. They detect chemical and mechanical signals in the gut environment — the presence of nutrients, the stretching of the gut wall as food moves through, the composition of the microbiome around them, the presence of inflammatory signals — and they respond to those signals by releasing serotonin into the gut lining.

That serotonin then does several critical things. It regulates gut motility — the muscular contractions that move food through your digestive tract. It modulates pain and pressure sensitivity in the gut. It communicates with the immune cells embedded in the gut lining. And most importantly for the conversation we are having today — it signals upward through the vagus nerve to the brain, where it shapes mood, emotional regulation, stress resilience, and sleep.

And here is the critical piece: EC cells do not operate in isolation. They are in constant chemical conversation with the microorganisms living in your gut — your gut bacteria. The health, diversity, and composition of your microbiome directly determine how well your EC cells produce serotonin. A rich, diverse microbiome stimulates robust EC cell serotonin production. A depleted microbiome produces impaired EC cell function — and with it, impaired serotonin signaling to the brain. This is the mechanism behind the connection between gut health and depression.

Approximately 90 to 95% of your body's serotonin is produced in your gut — primarily by those enterochromaffin cells — not in your brain.

The serotonin produced in your gut does not cross the blood-brain barrier to directly lift your mood. Instead, it works through the gut-brain axis — communicating states of gut health or distress upward through the vagus nerve, which the brain then translates into emotional and psychological experience. A healthy gut with well-functioning EC cells sends signals of calm, safety, and emotional stability to the brain. A dysbiotic, inflamed gut with impaired EC cell function sends distorted signals that the brain experiences as anxiety and low mood.

1. Eat tryptophan-rich foods daily. EC cells require tryptophan — an essential amino acid — as the raw material for serotonin production. Without adequate dietary tryptophan, even healthy EC cells cannot produce optimal serotonin. The best sources are turkey, chicken, pasture-raised eggs, wild-caught salmon, pumpkin seeds, and full-fat dairy. Pair them with complex carbohydrates for better absorption into the gut lining. For example, turkey or eggs with sweet potato.

2. Feed the bacteria your EC cells depend on. Your EC cells respond directly to the chemical signals produced by gut bacteria. Daily fermented foods — plain yogurt, kefir, refrigerated sauerkraut, and kimchi — replenish the Lactobacillus and Bifidobacterium species that most directly stimulate EC cell serotonin production. Consistency matters far more than quantity — a few tablespoons of sauerkraut daily produce meaningful microbiome shifts over weeks.

3. Get morning sunlight and move your body. Natural morning light and physical movement both stimulate serotonin synthesis — the combination of a 15-minute morning walk outside is one of the most powerful, most accessible, and most underutilized serotonin interventions available. It costs nothing and the biology behind it is unambiguous.

4. Protect and activate your vagus nerve. Because EC cell serotonin communicates with your brain through the vagus nerve, the tone of that nerve directly determines how well the serotonin signal is transmitted. Extended exhale breathing, humming, cold water on the face, and prayer and stillness all activate the vagus nerve and improve the gut-to-brain serotonin communication pathway.

I have always been in awe of the human body and how it works. The flawless design. The intelligence throughout every system, every cell, every process and without having to even think about it. Learning about serotonin—that it begins not in the gut but in the brain—has only deepened that wonder for me. God did not design us haphazardly, but with great intention and intelligent design.

Scripture tells us we are fearfully and wonderfully made. Fearfully —to treat our body with reverence and care. Wonderfully— realizing the beauty and complexity of our body.

Perhaps the most hopeful truth of it, is the path to emotional wellbeing runs through something we can actively nourish and restore.

"He heals the brokenhearted and binds up their wounds." — Psalm 147:3

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Your serotonin is not primarily a brain problem. It is a gut problem — specifically, it is an enterochromaffin cell problem, rooted in the health of the microbiome those cells depend on to do their job.

The path to restoring it runs through what you eat, how you sleep, the bacteria you nourish, and the vagus nerve you activate every single day.

Your body was beautifully and intentionally designed. Nourishing it the right way will help you to not just survive, but to truly thrive.

With faith, science, and wellness,
Liz, The Wellness Nurse

Registered Nurse | Certified Mental Wellness Coach

P.S. Have you ever wondered whether your mood challenges were rooted in your gut? Hit reply and tell me your story- I would love to hear it.

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