When your gut controls your mood: the gut-brain axis

From as early as the 1930’s, scientists were beginning to understand that the health of our digestive system could influence our mood.  The state of our intestinal lining and the balance of bacteria within our digestive system have a major role to play in the production of our neurotransmitters: chemical transmitters that tell our brain whether we should be feeling such ways as happy, sad, agitated, or calm.  But even though the research in this area sky-rocketed in the last decade and continues to grow every day, the concept of our gut-brain connection isn’t very well known.

The gut is linked to the brain

Did you know – When you were just starting to grow in your Mumma’s womb, your brain and your digestive system developed from the same lump of tissue.  During this process of dividing up cells (embryogenesis) this lump of tissue divides and forms our central nervous system and our enteric nervous system (this is the nervous system of our gut – sometimes called the second brain).  These two are connected by an important ‘wire’ – our vagus nerve.  This development can help us understand why there are so many similar chemicals and receptors in both our brain and our digestive system, for instance serotonin.

Gut bugs and your mood

As soon as you’re born, bacterial colonies start to develop in your digestive system.  Within the first few days, the bacteria starts sending messages to the nervous system and can actually determine our nervous system ‘set point’ long term (1).

When the balance of our gut bacteria (collectively referred to as the microbiome) is affected, this can affect your mood.  Studies have found that the microbiome can have a major impact on stress levels and anxiety (2).  In fact, by treating imbalances in our microbiota, it is possible to support a wide range of mental health disorders (3), (4), (5), (6), (7).

The second brain

The nerves in your digestive system are constantly speaking to your central nervous system.  If your gut is irritated for some reason – say you’ve eaten something that you’re intolerant to (like gluten, for example), you’ve generally got a bad diet, there’s an imbalance in your microbiome (that’s your collective gut bacteria, remember) or you’ve got an infection – this can create an inflammatory reaction and will certainly make you irritated as well.  We know that depression is both associated with, and worsened by inflammation.  This inflammation in the brain can be driven by inflammation in the gut, which can be caused by intestinal permeability (leaky gut) and bacterial imbalances (dysbiosis).  Treating leaky gut can help reduce the severity of depression (4), (8), (9), (10), (11).

Neurotransmitters in our gut

Serotonin is produced in large amounts in our digestive system.  In people with Irritable Bowel Syndrome (IBS) there is too much serotonin in their digestive system.  This is why antidepressants known as SSRI (selective serotonin reuptake inhibitors) can improve the symptoms of IBS: these act by reducing the amount of serotonin taken into cells in the rest of our body which allows more to get into the brain.  However anti-depressants can affect the gut negatively as well, because if you weren’t making enough serotonin in the gut in the first place, you’d end up with even lower levels in the digestive tract and so it can become irritated, affectively you’ll get a depressed gut (12), (13).

A vicious cycle

When your gut is upset, you feel upset.  But stress can affect your digestive system just as much as it affects your mood.  It can impair the secretion of digestive acids, slow down the motility of the gut, allows the unfriendly bacteria to grow, reduces your friendly bacteria and exacerbates intestinal permeability (leaky gut) (14), (8).  This is a recipe for an unhappy digestive system, and as you know this can then go on to send more messages to your brain: so you can see how the cycle continues.

People with gut problems are more likely to experience anxiety and depression.  Some studies have found a high proportion of anxiety in those with gut conditions such as Irritable Bowel Syndrome(IBS), Crohn’s disease and coeliac disease (15), (16), (17).

Helping the gut-brain axis.

By treating digestive problems, sealing leaky gut and balancing your microbiome it is possible to help with conditions such as anxiety and depression, and there’s even research showing the benefits of treating the gut in conditions like chronic fatigue syndrome, schizophrenia and autism (10), (18), (11).  Probiotics are one of your major tools when it comes to treating the gut, but it’s a good idea to consult with a health practitioner to make sure you’re getting the right type, and also to get a good gut healing treatment program to go along with it ⁽¹⁹⁾, (4), (9).

Related articles:

• Probiotic stress busters: http://www.naturopathnsw.com.au/probiotic-stress-busters
• Depression starts in the gut?:  http://www.naturopathnsw.com.au/depression-begins-in-the-gut
• What is Dysbiosis: http://www.naturopathnsw.com.au/what-is-dysbiosis
• Fermented foods (foods to stop bloating and farting): http://www.naturopathnsw.com.au/foods-to-stop-bloating-and-farting-fermented-foods
• Enhance your health with probiotics: http://www.naturopathnsw.com.au/enhance-your-health-with-probiotics
• The benefits of soaking and sprouting: http://www.naturopathnsw.com.au/the-benefits-of-soaking-and-sprouting-plus-a-sprouted-chickpea-hummus-recipe

Works Cited

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