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The Gut, the Microbiome, and the Power of the Second Brain

The digestive system extends beyond its role in food processing. Often termed the "second brain," the gut contains a complex, autonomous network of neurons known as the enteric nervous system (ENS), which possesses the capacity to function independently of the central nervous system.

BBan biên tập SciencepediaPublished Sep 09, 20262 min read1

Contents

Notable figures
Why is the gut called the "second brain"?
Autonomic digestive system control
Close connection to emotions
Gut microbiome
How do gut bacteria influence appetite?
Impact on neural signaling
Can the gut microbiome be "reprogrammed"?
Conclusion
Further reading

Notable figures

Approximately 500 million neurons are located in the enteric nervous system.
About 95% of the body's serotonin is produced in the digestive tract, with only about 5% created in the brain.
The vagus nerve connects the brain and the gut, with the majority of signals transmitted from the gut to the brain.

Why is the gut called the "second brain"?

Autonomic digestive system control

The gut can control itself through:

Peristalsis.
Secretion of digestive enzymes.
Nutrient absorption.

all without constant commands from the brain.

Close connection to emotions

The brain and gut communicate constantly via the Gut-Brain Axis.

This is why:

Stress can cause stomach pain or diarrhea.
Intestinal issues can affect mood and sleep.

Gut microbiome

The gut contains trillions of microorganisms that form the Gut Microbiome.

These microorganisms produce various chemicals that play a role in neural communication and influence:

Appetite.
Metabolism.
Mood.
Overall health.

How do gut bacteria influence appetite?

Impact on neural signaling

Gut bacteria can produce chemicals that influence vagus nerve activity, thereby affecting the centers that control feelings of hunger and satiety.

Ghrelin (the hunger hormone).
Leptin (the satiety hormone).
PYY and GLP-1 (hormones that help reduce appetite).

Can the gut microbiome be "reprogrammed"?

It is possible to change the composition of the microbiome through diet.

Beneficial habits include:

Eating plenty of vegetables and fruits.
Increasing fiber intake.
Consuming fermented foods such as yogurt and kimchi.
Limiting sugary drinks and ultra-processed foods.

These changes can influence appetite and digestive health over time.

Conclusion

🧠🦠 The gut does not literally "think" like the brain, but it possesses a complex nervous system and communicates constantly with the brain through the Gut-Brain Axis. It is this connection that makes gut health significantly influential on human digestion, appetite, mood, and overall health.

Notable figures

Approximately 500 million neurons are located in the enteric nervous system.
About 95% of the body's serotonin is produced in the digestive tract, with only about 5% created in the brain.
The vagus nerve connects the brain and the gut, with the majority of signals transmitted from the gut to the brain.