Last updated June 29, 2021 by Lisa Richards, CNC   Reviewed by Katie Stone, ND.

What Is the Gut-Brain Axis, And Why Does It Matter?

The gut-brain axis

Have you ever had ‘butterflies in your stomach’ before an exam? Or grieved so deeply that you’ve lost your appetite?

It’s not all in your head; the gut is more closely linked to your brain than you realize.

What Is The Gut-Brain Axis?

As you may already know, your gut flora play a key role in keeping your body healthy – which is why it’s important to support the balance of beneficial bacteria in the gut. But did you know they play a role in your mental health as well?

To understand the ‘gut-brain axis’, it’s important to first understand the enteric nervous system. The enteric nervous system is a vast network of neurons that line your intestinal tract and carry messages from the gut to the brain, and back.

Researchers have found that a direct line of communication exists between the brain and your enteric nervous system: this is what they call the gut-brain axis. This line of communication works both ways, linking the emotional and cognitive centers of the brain with peripheral intestinal function.

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That’s why the gut is also known as ‘the second brain’. The composition of your gut flora can change the signals that are sent from your gut to your brain. So an aggressive pathogen like Candida can literally change the way that you think.

The Link Between Your Gut and Your Brain

It’s not just your digestion and immune system that your gut microbiota is involved with – but your brain as well.

Amazingly, the microorganisms in your gut have been shown to interact with the nervous system, influencing all the messages and actions sent from the brain around the body. The mix of bacteria and yeast in your intestines can affect the messages and chemicals associated with your body’s response to stress, anxiety and even memory function.

The brain communicates with your gut via the parasympathetic, sympathetic and enteric nervous systems.

  • Parasympathetic nervous system: This is your body’s ‘rest and digest” response which controls digestion and relaxation. It conserves energy, slows heart rate, increases digestion, and relaxes sphincter muscles in the digestive tract.
  • Sympathetic nervous system: This is your body’s ‘fight or flight’ response which prepares the body to run away from a threat by stimulating blood-flow to major muscles, and restricting gut motility.

In fact, up to 90 percent of the cells involved in digestive sensations carry information TO the brain rather than receiving messages from it. This means your gut can influence your mood as much as your thoughts do!

Why The Gut-Brain Axis Matters

There are several reasons why the gut-brain axis can explain why you act and feel the way you do. If you feel cranky, irritable or depressed, it could be that your gut microbiota is out of balance. In the same way, your emotions and thoughts can affect how well your body digests food!

  • The health of your gut microbiota has a major impact upon your thoughts, emotions and mood. If the gut is inflamed, bloated or uncomfortable in any way, your gut microbiota sends this information to the brain – which can directly affect your mood.
  • Digestive discomfort, triggered by a Candida overgrowth or poor digestion, can both be caused by and contribute to low mood. This also means that irritation in the gastrointestinal tract may result in signals to the central nervous system that influence mood.
  • Those with IBS are often found to have higher rates of sympathetic nervous system function and lower rates of parasympathetic function. It also suggests that those with IBS are more prone to stress.
  • Stress stimulates the sympathetic nervous system, which leads to a decrease in digestive function and therefore pain, discomfort and altered bowel motility.
  • Studies have shown that almost 50% of patients with diagnosed with IBS have small intestinal bacterial overgrowth (SIBO). SIBO is a condition similar to Candida overgrowth, and is associated with conditions such as depression and some chronic digestive disorders.

In a nutshell: an upset gut can send distress signals to brain, just as an upset brain can send distress signals to the gut. Your stomach or gut problems may be the cause of your mood swings, depression, stress or anxiety.

Supporting The Gut-Brain Axis For Better Health

Imbalances in gut flora can lead to an overgrowth of potentially harmful bacteria and yeasts like Candida. This can lead to not just digestive symptoms, but mental and emotional issues as well. That’s why it’s so important to look after the health of your gut while also looking after your mind! Here are some ways to keep the gut-brain axis in balance:

  • Eat plenty of whole, natural foods to support healthy gastrointestinal microbiota. Look for natural prebiotic foods such as garlic, onions, asparagus, leeks, and seaweed.
  • Supplement with probiotics to boost numbers of ‘good’ bacteria, especially if you’re experiencing symptoms of dysbiosis. Look for a probiotic that will actually get its bacteria past your stomach acid and to your gut, like this one.
  • Avoid or limit things that can destroy the healthy microorganisms in your gut, such as processed food, alcohol, antibiotics, excess fat, and sugar.
  • Support your mental health by taking time out to relax. Meditate, do yoga, or just do something you enjoy.
  • Improve your physical and mental health by getting regular exercise such as walking, swimming or running.

Healthy Gut, Healthy Mind

The link between the gut and the brain is best understood when you’ve experienced the symptoms first-hand. If you suffer from low mood, fatigue and anxiety, your gut might be part of the problem. Looking after your gut will benefit your mind – just as looking after your mind will benefit your gut!

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  1. Lorraine Cullum says:

    I have been diagnosed with heavy overgrowth of candida and also imbalanced flora called citrobacter Freundi complex and dysbiotic flora called citrobacter farmeri levels are 4+ and klebsiella oxytocin levels are 4+.
    I am in so much pain I need help.

    1. Lisa Richards says:

      Firstly, it’s great that you got tested! Those bacteria and the Candida are all OK in small amounts, but when they overgrow they can start to cause significant health problems. Especially if your levels of Lactobacilli and Bifidobacteria bacteria are to low (these should also be listed in your test results). I would recommend speaking to your family doctor, and maybe getting a referral to a gastroenterologist, to rule out serious health issues. If it’s purely gut-related, and due to triggers like antibiotics or a high-sugar diet, then you can think about adopting some of the dietary/lifestyle tips on this site. It’s a good idea to have someone work through this with you (e.g. an integrative doctor), and do repeat testing along the way. I hope that helps!

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