The gut-mind connection

Updated: Apr 5

Those butterflies in your stomach actually hold some scientific truth.

No… you don’t actually have butterflies pirouetting into a tornado of torment when you are nervous, but you do have millions of nerves branching from your gut up to your brain. Your gut health affects your thoughts, feelings, memory, anxiety, depression, cravings, eating behaviours and life choices. They call it the gut-mind connection.

The way it works: You have a bunch of hormones and neurotransmitters sending signals along that gut-brain highway, as well as buckets of bacteria in your gut doing all sorts of things that affect how you think, feel and behave.

I recently presented a workshop on this topic at an exclusive health retreat in Byron Bay. Below is a brief overview of some of the sub-topics I covered. Contact me if you would like further information.

Gut feelings

We’ve all experienced them… those nervous feelings in our guts before a presentation, an exam, or starting a new job... Maybe you even feel that warm fuzzy feeling in your belly when think love.

These gut feelings are real. A good example of this is experienced when we are scared or fear for our lives.

Pretend that you are asleep and you wake up to find a snake in your pillow.

How do you feel?

During an experience like this, the brain sends signals to prepare the body for what is called the ‘fight or flight’ response.

  1. Adrenaline and cortisol are released into the blood

  2. Blood pressure, blood glucose levels and heart rate increase

  3. We get a boost of energy

  4. Digestion slows down or stops (the gut)

  5. We get anxious or aggressive

  6. We respond – kill that snake or run the other way

This ‘fight or flight’ response is regulated through the autonomic nervous system – a complex network of nerves that extend from the brain to all the major organs of the body, including the gut.

The body’s 2nd brain

The gut has been dubbed the body’s second brain. It contains over 500 million neurons (nerve cells) and plays a crucial role in both our digestive health and body systems, including our minds.

The guts neurons and neurotransmitters (nerve messengers) are the same as those found in the brain and spinal cord. They share similar functions and act in similar ways.

The gut nerves are collectively known as the enteric nervous system. All of these nerves eventually join up into a larger nerve, called the Vagus nerve – which connects directly with the brain.

If you can imagine a tree, all the branches would be the nerves surround the gut, the trunk would be the Vagus nerve, and the roots would be the brain in your skull.

If the Vagus nerve is blocked or damaged, it has profound effects on your gut health, including affects on digestion, appetite and eating behaviours.

Eating food

When we eat food, the nerves in the gut are stimulated, which then trigger the muscles in the digestive tract to contract and move the food forward. At the same time neurotransmitters, such as serotonin, are released from the gut to communicate messages back and forth to the brain. These messages affect our appetite and our feelings of fullness, as well as regulate the movement of food through our digestive tract.


It’s not only our bodies that are working on digesting and absorbing the foods we eat, but also the bacteria that live within our guts; these guys play an integral role in our health.

Gut bacteria - we are more than human

“One linear centimeter contains more bacteria than all the humans that have ever been born.”

The human gut contains 2-3kg of bacteria. These bacteria are referred to as microflora and outnumber our body cells by 10 to 1 - the human body contains about 10 trillion cells. (10 x 10 TRILLION BACTERIA IN OUR GUTS).

There are over 1000 different species of gut bacteria. Like a bird on a cow, majority of these live in harmony with us. They provide benefits such as helping with digestion, immune support, as well as producing some essential fatty acids and vitamins that support a healthy body.

If pathogenic (bad) bacteria move in and grow in undesirable numbers, they can damage our health (e.g. gastroenteritis) - Vomiting. Diarrhoea. Pain. Inflammation. Etc.

Some of the nerve fibres from the enteric nervous system (the gut nerves) protrude out into the gut and make contact with some of these bacteria - one of the reasons why we get abdominal pain and suffer other unhappy symptoms when we have a gut bug.

Gut bacteria therefore define a healthy or unhealthy gut.

Your gut health affects your thoughts, feelings and choices.

Some of the evidence

2 hormones/neurotransmitters associated with the gut-mind connection…


  • Functions = feelings of reward/pleasure, appetite and compulsions

  • ~50% of dopamine is produced in the gut

Gut-mind link (evidence on Dopamine)

  • Gut bacteria - can produce vast amounts of dopamine, influencing appetite, reward, motivation, pleasure and gastrointestinal motility (movement of food).

  • Parkinson’s disease – a degenerative condition that causes tremor and motor impairment is caused by a loss of dopamine-secreting neurons

  • Antipsychotic drugs – are dopamine antagonists (reduce dopamine activity)

  • Anti-nausea drugs - dopamine antagonist drugs (reduce dopamine activity)

  • ADHD - Scientists have observed that lower levels of dopamine are associated with symptoms of ADHD


  • Functions = regulates mood, cognition, memory, sleep and appetite

Main role - digestion and movement of food through the intestinal tract

  • Virtually all of the serotonin produced in the body (~90%) is made in the gut.

Gut-mind link (evidence on Serotonin)

  • Serotonin is a key neurotransmitter in the gut-mind connection.

  • Depression - deficiency of serotonin is linked to depression.

  • Anxiety – alterations in serotonin levels.

  • Food cravings – alterations in serotonin levels.

  • Anti-depressants and anti-anxiety medications – SSRI’s are the most commonly used and act to increase levels of serotonin in the circulation. Common side effects of SSRIs are nausea, diarrhoea and weight gain (the gut).

  • Tryptophan – is an amino acid that is required to make serotonin. Low tryptophan levels have been associated with memory alterations, lower mood and increased irritability and aggression. Tryptophan levels are affected by gut bacteria.

  • Gut bacteria - produce factors that can block or mimic serotonin action, and hence influence mood, cognition, sleep, appetite and digestive health.

Gut bacteria can influence your mind

So your gut microflora can influence how and why you may eat, your memory, your mood and your sleep.

They can do this directly, via mimicking the hormones normally produced by the gut.

They can do this indirectly, via stimulating things that will block hormone signaling.

Some studies have shown the following:

  • 50-90% of patients suffering from Irritable bowel syndrome have issues with anxiety, depression, panic disorders or social problems.

  • By changing gut microflora activity, food cravings can be reduced

  • Altering gut microflora can influence and potentially cure food allergies

  • Increased microflora diversity can improve food choices and satiety (feeling satisfied)

Symptoms of anxiety, nervousness, depression and even fatigue can be traced back to altered gut microflora.

Healthy gut = healthy mind = healthy gut

What can you do?

  • Eat a diet rich in both probiotic and prebiotic foods

  • Eat a well balanced, nutrient rich diet

  • Manage your stress levels

  • Move your body

  • Sleep well

My next blog post will focus on foods to optimise your gut health.

For more information on our health retreats, check out the link here SOL retreats.