Gut and Brain Axis – How Does The Gut Affect The brain?

When a person suffering from depression and anxiety goes to their local GP, they are often prescribed with antidepressants and anxiety medication. When a person complaining of a bowel issue goes to their GP they are treated for something completely different.

Or should it be different?

Over the past few years there has been numerous studies done on the relationship between the gut and the brain and why some mental health issues (physiological) could just be SYMPTOMS of an underlying intestinal problem (physiologically).

How can the gut and the brain be linked? It seems very surprising, to me anyway, that an organ as complicated and sophisticated as the brain is so easily affected by a part of the body that gets overlooked so often throughout the day.

And scientists have made an incredible discovery that the Gastro- Intestinal tract (GI tract) plays a critical role in how well the brain functions.

So today, I thought I would write about this Gut and Brain Axis and explain why the answer to the mental health crisis could be found, not in our heads, but in our bellies; And that the problem is not psychological but physiological.

Our Bodies are Home to Other Organisms.


Most people go about their lives completely oblivious to the fact that their bodies are home to trillions of other living organisms.

Millions of fungi, bacteria and viruses live on and within our bodies too tiny to be seen by the human eye.

Scientists have mainly focused their research on the bacteria in the body as it seems most of the benefit is attributed to these little guys.

Shockingly, there are more bacterial cells in your body than human cells.

There are approximately 40 trillion bacterial cells (Around 1-2kg worth of bacteria!) in your body and only 30 trillion human cells. That means there are more bacteria than there is you, inhabiting you.

This is why scientists have decided to call this mass of bacteria the ‘Body’s Extra Organ’. Most of this ‘organ’ is found within our large intestine.

These microbes can help fight off bad bacteria and yeasts within the gut, improve the body’s immune system, help the cells absorb fatty acids, digests carbohydrates, produce vitamins B and K for the body and even produce serotonin- the body’s “happy” chemical.


Can my gut bacteria heal my mental illness?

As mentioned in the last paragraph, the gut’s flora or ‘microbes’ can produce serotonin in the body. In fact, 90% of serotonin is produced in the gut.

In the study “Serotonin, tryptophan metabolism and the brain-gut-microbiome axis“, it explains how the brain-gut axis “is a bidirectional communication system between the central nervous system and the gastrointestinal tract [gut].”

Serotonin is used as the primary neurotransmitter at both ends of this brain-gut axis and evidence suggests that the “gut microbiome plays a critical role” in making sure this axis is working efficiently.

The study concludes that there is a definitive link between the gut microbiota and serotonin levels. “Therapeutic targeting of the gut microbiota might be a viable treatment strategy for serotonin-related brain-gut axis disorder”.

This means that any mental illness associated with lack of serotonin such as major depressive disorders, as well as other mood disorders, anxiety disorders, schizophrenia, addiction, attention deficit hyperactivity disorder (ADHD), and even autism can be treated by focusing on improving the gut microbiome.

The Entric System – the Gut’s Personal Nervous System:

The Enteric Nervous System (ENS) is defined as the arrangement of neurons and supporting cells throughout the gastrointestinal tract, from the esophagus to the anus (Goyal and Hirano, 1996).

The Gut-Brain Axis talks to each other through biochemical signaling between the ENS, the Gut’s personal nervous system, and the central nervous system, which includes the brain.

ENS is a very complicated system of millions of neurons(as many as the spinal cord) that control the behaviors in the gut independently of the central nervous system (CNS).

ENS is often called the “second brain” by scientists or “the brain in the gut” because it can operate independently of the brain and spinal cord. Interestingly, researchers also call it the “first brain” because they have found evidence that the ENS could have existed long before the CNS.

I have included this short YouTube video that explains this is more detail:

‘The Second Brain’ Book Available Online:

I have read many books on this topic in the hope I can learn more on how to treat mental health problems with food. Here are two of the best books I have read so far on the subject:

The Second Brain“: The Scientific Basis of Gut Instinct and a Groundbreaking New Understanding of Nervous Disorders of the Stomach and Intestines” by Dr. Michael D. Gershon: It goes into more detail than I have on this article, and I advise anyone wanting to better their mental state, Gastrointestinal issues, heartburn problems, or overall energy levels to read this book.

You can save money on medication for these problems by simply educating yourself about how your body works.

–>Available on Amazon; click the link here<—

Bacteria that can affect behavior and thinking:

It is very important to eat foods that will put these good microbes in your gut so you can receive health benefits.

Gut bacteria affects brain health, so changing your gut bacteria may improve your brain health.

Probiotics are defined by the Oxford dictionary as a microorganism that is introduced into the body for its beneficial qualities. However, not all probiotics are the same. My advice is to consult a doctor/dietitian about which probiotics to use; there are also various companies that can send you a stool sample test kit, that you can then send to a laboratory for analysis.

Probiotics that are specifically for targeting the brain are called “Psychobiotics“, a term that was first coined by Professor Ted Dinan of University College Cork in Ireland. These types of microbiota, according to researchers, could potentially have the same impact on the brain as medication does.

One of the pioneering studies led by Premsyl Bersick, proved that stomach bacteria could affect cognitive behavior. In the study they took fecal transplants from mice that were genetically bred to be confident and curious, and transferred it to mice that were genetically bred to be anxious and reserved.

Incredibly, the timid mice after the transplant began to behave in much the same ways as the confident and curious mice. Unfortunately fecal transplants are still not readily available to people as studies are still being carried out.

Nonetheless, this suggests that such “psychobiotics” could have a tremendous effect on people’s behavior and cognitive functioning.

What can i eat to boost my good bacteria?

In order to have a healthy amount of good bacteria, make sure you are eating plenty of fermented foods.

Fermented foods contain healthy bacteria, some examples are listed below:

  • sauerkraut
  • kefir
  • non-pasteurized yoghurt
  • Miso soup
  • bone broth (chicken or fish)
  • Dark green vegetables
  • Kimchi
  • Kombucha
  • ginger
  • tumeric
  • lemon juice (organic)

Supplements I recommend: “Garden of Life Dr. Formulated Probiotics Mood+ – Acidophilus Probiotic Supplement – Promotes Emotional Health, Relaxation, Digestive Balance – Non-GMO, NSF Gluten Free – 60 Vegetarian Capsules”. Available on Amazon click here

Ketogenic Diet and Fasting. The Keto diet (high fat low carb)and fasting have been shown to improve gut health.

I have written a lot on these two topics already if you would like to take a look:



Thanks so much for reading! If you have any questions or anything you would like to add please feel welcome to leave them in the comment section down below! 🙂


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