What is the gut-brain axis?
There’s been a lot of talk about the gut-brain axis, but what is it? Simply put, it is the communication between your gut (gut microbiome) and your brain. The gut microbiome can influence brain function and mental health through neural, hormonal and immune pathways–and for this reason it’s also known as the ‘second brain’.
Your gut and your brain are constantly communicating, and disruptions in one area can easily impact the other. For example, disruptions in gut health can contribute to anxiety, depression and brain fog. On the flip side, improving gut health has been shown to enhance mood, focus, and cognitive performance.
How the gut impacts brain and mental health
The gut microbiome is made up of trillions of microorganisms such as bacteria, fungi and viruses that call our digestive tract home. They are vital for digestion and immune function and produce essential neurotransmitters like serotonin that influence mental health and cognitive function.
Before we get into the benefits of a healthy gut on the brain, we need to understand that the gut-brain axis works through several pathways:
Neuronal Communication
The vagus nerve is the main communication pathway between your gut and brain, connecting the gut, heart, and lungs to the brain. It sends signals from the gut to the brain and vice versa. For example, when the gut experiences stress, signals are sent through the vagus nerve to the brain and these can impact mood and cognitive function. Similarly, stress from the brain can disrupt the gut leading to issues like IBS.
Neurotransmitters
As I mentioned earlier, neurotransmitters (chemicals that influence brain activity) are produced by the gut. These are:
- Serotonin: About 90% of serotonin, the "feel-good" hormone, is produced in the gut. Serotonin influences mood and helps prevent depression and anxiety. A healthy balance of serotonin is essential for both emotional wellbeing and proper bodily functions.
- GABA (Gamma-Aminobutyric Acid): Another key neurotransmitter produced in the gut helps regulate feelings of calm and reduces anxiety. An imbalance in the gut can lower levels, contributing to heightened anxiety and stress.
Gut Microbiome
The gut microbiome is essential in regulating brain chemistry and overall mental health. A balanced microbiome produces short-chain fatty acids (SCFAs), which reduce inflammation, protect the brain, and promote healthy brain function. However, an imbalanced microbiome can lead to:
- Increased inflammation in the body which negatively impacts brain health.
- Reduced production of neurotransmitters like serotonin and GABA.
- Altered communication between the gut and brain which contributes to mental health disorders like depression and anxiety.
Key Benefits of a Healthy Gut on Mental Health
A healthy gut has been proven to have a positive impact on your mental health and wellbeing. Here’s how:
- Mood Regulation: A balanced gut microbiome promotes the production of serotonin and other neurotransmitters that regulate mood.
- Reduced Anxiety and Depression: A balanced gut microbiome reduces feelings of anxiety and depression.
- Emotional Stability: A healthy gut can help stabilise emotions and reduce mood swings.
A 2023 study published in Nature Communications examined data from over 2,500 adults to better understand the link between gut bacteria and depression. The research found that the presence or absence of certain gut bacteria, such as an overabundance of Eggerthella, was associated with higher depressive symptoms, while other bacteria like Subdoligranulum were associated with fewer symptoms. This highlights how gut health influences wellbeing and supports the role of diet in managing depression.
Key Benefits of a Healthy Gut on Cognitive Function
In addition to mental health, gut health plays a crucial role in cognitive function:
- Improved Focus: A healthy gut supports better concentration and mental clarity, helping you stay focused and productive. This is because the gut produces neurotransmitters and other compounds that influence attention and alertness.
- Increased Energy: The gut helps regulate energy levels, and a healthy gut microbiome ensures your body efficiently processes nutrients for sustained energy.
- Enhanced Cognitive Performance: A balanced gut can boost memory, cognitive sharpness, and overall brain function. The gut’s impact on inflammation and neurotransmitter production directly supports brain health, improving tasks like memory recall and problem-solving.
A systematic review and meta-analysis investigated the effects of probiotics on cognitive function. The results showed that supplementing with specific strains like Lactobacillus and Bifidobacterium improved cognitive performance, particularly in older adults experiencing mild cognitive impairment. These improvements were linked to better gut microbiome balance, which reduced inflammation in the body, thus positively impacting attention, memory, and mental clarity. This shows that targeting the gut with the right probiotic strains can improve cognitive function and increase energy and focus.
How to Support a Healthy Gut for Brain Health
At this point it’s quite clear that a healthy gut is a powerful way to improve your mental health and cognitive function. Here are a few simply ways you can improve your gut health:
- Eat more fibre: Fibre-rich foods like vegetables, fruits, and whole grains promote the growth of beneficial bacteria in the gut.
- Incorporate fermented foods: Foods like yoghurt, kimchi, and sauerkraut contain probiotics that help balance gut bacteria.
- Take prebiotics and probiotics: Prebiotics (found in foods like garlic, onions, and bananas) feed the healthy bacteria in your gut, while probiotics (live beneficial bacteria) improve gut health.
