Serotonin: Why Your Gut Produces 95% — And What Diet Really Changes

by Laurent Glatz – for Athletic Carnivore

In 2018, a research team at the Mayo Clinic uncovered a key mechanism behind intestinal serotonin release. Their discovery focused on a microscopic structure called Piezo2, an ion channel sensitive to mechanical forces.

In other words: a pressure sensor.

This finding sheds light on a phenomenon physiologists have long observed. When food enters the intestine, certain cells release serotonin in large amounts.

But it’s neither the taste of the food nor its chemical composition that triggers this.

It’s the physical pressure of digestion.

95% of Serotonin Comes From the Gut

To grasp the significance of this discovery, we must recall a fundamental biological fact: about 90 to 95% of all serotonin in the human body is produced in the gut, not the brain.

This production occurs in specialized cells called enterochromaffin cells. They line the intestinal mucosa and form one of the major interfaces between the digestive system and the nervous system.

Embedded in their membrane is the Piezo2 channel. When the intestinal wall stretches as food arrives, the cell membrane deforms. This deformation opens the channel. Ions then enter the cell, creating an internal electrical signal that triggers serotonin release.

Digestion thus becomes not only a chemical but also a mechanical process.

Pressure Triggers Chemistry

Every movement of food through the intestine exerts pressure on digestive tissues. This pressure activates the Piezo2 mechanoreceptors. Enterochromaffin cells release serotonin.

The effect is immediate: serotonin activates the enteric nervous system, sometimes called the second brain. This neuronal network in the gut contains about 500 million neurons and controls digestive motility.

Serotonin acts as a messenger. It stimulates muscular contractions of the digestive tract, coordinates peristalsis, and facilitates the progression of food through the intestine.

Without this chemical signal, digestion would become slow and chaotic.

A Digestive, Mechanical, and Metabolic Molecule

Intestinal serotonin doesn’t remain confined to the gut. Some is taken up by blood platelets and circulates throughout the body. It participates in vascular regulation, immune communication, and certain metabolic signals.

This mechanism also contributes to the gut-brain axis — the ongoing communication between the digestive system and the central nervous system via the vagus nerve and several hormonal pathways.

In other words, part of what we call mood could be indirectly influenced by what happens in our digestive tract.

What Does Diet Change?

This reality raises a question science is only beginning to explore: what happens when diet changes radically, as in low-carb or carnivore diets?

In a diet rich in carbohydrates and plant fibers, intestinal volume is generally larger. Fibers absorb water, increase the bulk of the food bolus, and cause greater intestinal distension. This distension can strongly activate Piezo2 mechanoreceptors.

In a carnivore or very low-carb diet, digestion works differently. Proteins and fats are digested more efficiently in the small intestine and usually leave fewer bulky residues in the colon.

Mechanical volume may be lower.

But the relationship with serotonin is far more complex than this simple factor. Serotonin production also depends on tryptophan, an essential amino acid found in high amounts in animal-based foods: meat, eggs, fish.

Tryptophan is the direct precursor of serotonin.

The Brain May Not Be the Only Commander

Science has yet to definitively settle all the consequences of these dietary changes. But one thing is already clear.

Serotonin is not simply a happiness molecule produced by the brain.

It is a digestive, mechanical, and metabolic molecule. It depends on the pressure of food in the gut, the activity of Piezo2 mechanoreceptors, and the nutrients we consume.

In other words, our biological state may be influenced far more by the mechanics of our digestion than by our thoughts.

And if 95% of serotonin comes from the gut, then one question becomes hard to ignore.

Are we truly guided by our brain… or by how we eat?