How the Gut Controls our Thoughts and Moods (Gut-Brain Axis Part 1)

Have you ever been told to trust your gut feeling?  Well, it turns out, that your gut actually tells you a lot!

This week, we’re going to take a look at the “Brain-Gut” or "Gut-Brain" Axis and see how you get those “gut feelings,” why you should listen to them, and how to keep your gut healthy.


  1. Gut-Brain Axis Part 1
  2. Gut-Brain Axis Part 2
  3. Gut-Brain Axis Part 3
  4. Gut-Brain Axis Advanced

What’s The Gut?


So what do we mean by gut?  The gut can refer to the entirety of the human digestive system which includes your esophagus, your liver, and your gastrointestinal tract.  But it can also refer to the gastrointestinal (or GI) tract by itself.  When I talk about your “gut” this week, that’s what I’ll be referring to.

The GI tract is comprised of your stomach, intestines, colon and rectum which altogether weighs as much as your brain!  You’ve got more microorganisms in your gut than you have cells in your body and those microorganisms contain more than 100 times as many genes as the human genome.  All these microorganisms together are called your microbiota.

When we’re born, we have a low diversity of microorganisms in our microbiota.  Starting with contact with our mothers through breast feeding, our microbiota becomes more diverse.  Humans have been interacting with “good” microorganisms since the beginning of time and have evolved to need these microorganisms in our bodies.  These microorganisms produce nucleic acids that activate genes that benefit health and prevent diseases.

When there is something wrong with your microbiota, your whole body can be affected.  Dysbiosis is the scientific name for this microbial imbalance and it can be caused by many things like too much exposure to antibiotics, poor diet, or alcohol and drug abuse.  Although it can occur outside your gut (such as on your skin) it is most commonly associated with issues in the gut.

How Does It Work?

So how do the effects of your gut microbiota reach the brain and the rest of your body?  One way is through the intestines.  When you digest food, the nutrients are absorbed in the small intestine and transmitted to the rest of the body.  The acids from your microbiota (both good and bad) go along, too.

The second connection between the brain and gut is through the enteric nervous system or ENS.  The ENS is sometimes called the “Second Brain” because it is responsible for maintaining many vital functions throughout the body including the gut.  A major part of this is the vagus nerve.  The vagus nerve goes from your brain through your neck to your gut.  It travels to many parts of the body like a “vagabond.”   

In addition, the brain and gut are a two way street.  So, what is produced by the microorganisms in the gut can travel to the brain and signals from the brain can travel down to the gut.  As a result, many brain functions are particularly sensitive to changes in your microbiota.  I’ll explain these effects in my next post.

TLDR: The bacteria in our gut are vital for helping us stay healthy.

In My Next Post

Feel like you’ve experienced some brain-gut connection?  Send me your story on instagram!  For now, you can try these recipes:

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