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What is the Mind-Gut Connection?

Woman looking out to see, thinking about mind-gut connection, in red

Have you heard of the mind-gut connection? Our team has been reading so much about this trendy concept recently. As usual, we have questions and to help us answer them our wonderful naturopaths were on hand.  Here’s our Naturopath Kelly to simplify the mind-bending, mind-gut connection!

Kelly, is the mind-gut connection the same as a ‘gut feeling’?

It is – but it is also so much more! We have lots of phrases like this to describe the gut-level sensations we experience following particular thoughts or feelings.

We have a ‘gut feeling’ when we sense we know the right answer or approach without having to really think about it – we just know.  This is instinct – hardwired behaviour or knowledge that we can call upon without conscious thought.  And after our ‘gut feeling’, we may then ‘go with our gut’ to make a decision based on instinct or intuition alone.

Similarly, we might experience ‘butterflies’ in our stomach when we’re nervous.  Of course, there aren’t any actual butterflies in our stomach, but we know that fluttery feeling is located there. At times, we might have to make a ‘gut-wrenching’ decision or even feel ‘sucker punched’ in the gut when we’ve received shocking news.

So why do we feel these sensations in our gut when these thoughts and feelings arise from our brains?

The reason is because of our ‘gut-brain’ connection sometimes called the gut-brain axis or mind-gut connection.  This refers to the two-way communication network between our brains and our gut. This means the brain and gut are constantly in communication with each other and can influence how the other works.

The brain, of course, needs to keep tabs on the gut, like it does the rest of the body. It’s in charge.  But the gut can also influence how our brain works, having an impact on our thoughts, feelings and behaviours.  Scientists are making new discoveries all the time to understand how the gut can influence the brain and our moods.

Ok, so break that down, how does that two-way communication (the mind-gut connection) actually work?

The two-way communication network between our brain and gut occurs through a physical connection and a chemical connection.

The neuronal ‘superhighway’

The physical mind-gut connection occurs via the vagus nerve – the main ‘superhighway’ that links our brains to our gut.  This connection starts in utero with the brain and the gut originating from the same type of tissue. As the embryo grows, the brain stays at the top end and the gut slides down to other end with the vagus nerve serving to keep both connected.

In fact, our gut has such an extensive neuronal network of its own it’s been dubbed our ‘second brain’.  It’s other name is the enteric nervous system (ENS). Whereas our central nervous system (CNS), comprising our actual brain and spinal cord contain 100 billion nerve cells, our ENS contains 500 million nerve cells. That’s over 5 times more nerve cells than our spinal cord!  It’s our ‘second brain’ because it is capable of acting independently of our first brain (the CNS). This means it can carry out localised functions in the gut without the brain having any direct involvement at all.

Chemical messengers

The chemical connection between our gut and brain occurs in the form of neurotransmitters. These are substances that act as messengers moving between nerve cells to signal distant areas of the body to carry out specific functions.  Neurotransmitters are known to control our feelings and emotions. We know serotonin is associated with mood and happiness, and GABA is associated with feelings of calm and relaxation.

But the gut also produces many of the same neurotransmitters as the brain through specific digestive cells as well as by our gut bacteria.  In fact, in the case of serotonin, 95% of it is actually made in the gut! In our brain, it has a role in mood regulation (whether we are happy or sad) as well as our body clock.  But in our gut, it’s responsible for motility (how quickly or slowly food passes through), sensitivity (how likely we can feel gut sensations including pain) and also the secretion of fluids.

Other chemical messengers also play their part, including hormones and immune signalling chemicals.

Gut microbiome

The other important chemical connection between the brain and the gut is our intestinal microbiome or gut bacteria.  Not only are they capable of making neurotransmitters, they also produce chemicals known as ‘short-chain fatty acids’ (SCFA) by fermenting their favourite foods – dietary fibre and resistant starch.  SCFAs include the chemicals butyrate, propionate and acetate, which are also capable of affecting brain function. Butyrate, for example, helps to strengthen the protective barrier between the brain and the rest of the body called the ‘blood-brain barrier’ (BBB).  Propionate is capable of affecting appetite regulation by the brain.

What processes in the body are controlled or influenced by the mind-gut connection?

So both our gut and our brain can communicate back and forth and make substances that affect both our brain and our gut function.

It’s no surprise then that if one of these areas isn’t functioning as it should, it can have an effect on the function of the other.  This is why many gut disorders have a psychological impact, and why psychological stress can have a negative effect on our digestive function.

As another example – let’s look at the neurotransmitter GABA (gamma-aminobutyric acid). This is produced both in our brain and by microbes in our gut.  In our brain, it is associated with feelings of relaxation and calmness, and when deficient, with feelings of anxiety.

The gut is lined with receptors that bind GABA which indicate that GABA has a functional effect in the gut.  These functions include gut motility, gastric emptying, gastric acid production, lower esophageal sphincter relaxation and the visceral sensation of pain in the gut.

But research carried out on mice has also demonstrated how GABA-producing probiotic species (such as Lactobacillus rhamnosus JB-1)1 can also affect the GABA receptors in the brain reducing stress-induced anxiety and depression-like behaviour.  The study also found that when the vagus nerve was cut the beneficial effects ceased. This indicated that the vagus nerve was the main communication pathway between the gut and the brain.

Of course, there is a big difference between a mouse and a human! Mice don’t tend to be exposed to the many assaults (eg alcohol, cigarettes, bad diets, toxins and chemicals etc), that humans expose themselves to so it’s not possible to extrapolate findings from animal studies to the same direct effect in people. However, this is an exciting area of current research so it’s definitely a ‘watch this space’ situation!

So to look after our mind, we need to look after our gut health? Is there anything specific we can do for the gut to look after our mind in particular?

Yes!  When the gut is working at its best, the mind will follow – and vice versa.

To improve gut function that will have a beneficial effect on the brain, there are three main areas to consider.

  1. The health of the gut itself

This includes looking at how well our digestive system is currently functioning – are there any digestive symptoms suggesting that there is a problem with how it is working? For example excessive bloating may indicate an imbalance with between the beneficial and not so beneficial bugs in our gut, or it may suggest that you are eating a food that doesn’t agree with you.

It also involves understanding the health of the intestinal barrier – the layer of cells that line the gut and form a barrier between the gut and the body. A ‘leaky gut’ causes inflammation that can impact the brain.  It can occur when a person continually eats foods that do not agree with them or when their microbiome is not healthy and balanced.

Obviously, consideration of diet is crucial here as many of the reasons the gut becomes dysfunctional can be related back to eating the wrong foods.

  1. Vagus nerve ‘tone’

‘Vagal tone’ represents the activity of the vagus nerve and how well it’s working.  The vagus nerve is predominately associated with the ‘resting and digesting’ / parasympathetic nervous system.  This is an indication of how well our body can relax.  High vagal tone indicates we can more quickly initiate a calm, resting state after stress. Whereas low vagal tone suggests we aren’t as able to quickly recover from stress and that the ‘fight or flight’ / sympathetic nervous system is more overly activated.

We can activate the vagus nerve and improve its tone through a number of mechanism, including slow, deep breathing; exposure to cold, singing, humming or chanting; meditation; laughter; massage; exercise and supplementing with probiotics and omega 3 fatty acids.

  1. The health of your microbiome

That collection of living organisms that reside inside us is so important to our overall health that it’s essential to ensure that it is healthy and well balanced.

There are also other ways to support brain health outside of supporting our gut health too.  This includes getting plenty of restorative sleep.  Stress can also be harmful to the brain long-term so using techniques to manage stress such as mindfulness can also be beneficial.

 

Thanks to Kelly for answering our questions! If you have a question about the mind-gut connection, get in touch and we could answer it next time.

The Nutra-Life team x