The Gut-Brain Connection: Understanding the Gut-Brain Axis

What Is the Gut-Brain Axis?

The gut-brain axis is the term that refers to the communication network between your brain and gut. These organs are connected physically as well as biochemically through many different ways, such as the nerves, neurotransmitters and the immune system.

What systems constitute the gut-brain axis?

This bidirectional communication network includes:

• Central Nervous System (CNS): This constitutes your brain and spinal cord.
• Autonomic Nervous System (ANS): These are the nerve networks that handle unconscious tasks like heart rate, respiration, blood pressure and so on.
• Enteric Nervous System (ENS): Interestingly called the “second brain”, ENS is one division of the autonomic nervous system found on the walls of your gastrointestinal tract (from the oesophagus to the anus) that controls the digestive system.
• Hypothalamic-Pituitary-Adrenal (HPA) Axis: The HPA axis is one main neuroendocrine system of your body, involved in physiological homeostasis, stress response, and release of cortisol (stress hormone).

How Does the Gut-Brain Axis Work?

What does a two-way street do? It allows traffic to flow in both directions. This is exactly how the gut-brain axis works – your emotions can cause a stomach upset, and your gut health can influence your mood and behaviour.

What forms this two-way communication? 

1. Neural Pathways

Neurons are the structural and functional units of your nervous system. Neurons are distributed throughout your body but are most concentrated in your brain and spinal cord. 

Did You Know?

The enteric nervous system (ENS), the network of nerve pathways in your gastrointestinal tract, contains around 500 million neurons, making it the organ system with the second-largest number of neurons, after the brain and spinal cord, giving it the name “second brain”.

The vagus nerve is the main nerve that connects the gut and brain, which carries signals in both directions.

2. Neurotransmitters

How are messages transmitted from one nerve cell to another or to a muscle or gland? Here’s where chemical messengers called neurotransmitters come into play. 

Serotonin, a neurotransmitter, is a natural mood booster and regulates your sleep-wake cycles. Here’s something interesting – 90% of the total serotonin is produced in your gut. 

A study has shown that your gut microbiome (collection of microbes that live in your gut) can synthesise Gamma-Aminobutyric Acid (GABA), a neurotransmitter known for its calming and anti-inflammatory effect.

3. Immune System

Did you know that your gut houses about 70-80% of immune cells? The gut microbiome plays a significant role in the development of the gut immune system. Changes in your gut health or a disturbed balance of the gut microbiome can lead to inflammation, causing auto-immune disorders and mood changes.

The Role of Gut Microbiota

Not all bacteria are harmful; in fact, some are incredibly beneficial for your health. The term’ gut microbiota’ or ‘gut microbiome’ refers to a large group of up to 100 trillion microbes that reside in your digestive system and support digestion, boost immunity and maintain your overall health.

How do these microbes affect the gut-brain axis?

• A healthy gut microbiome produces and regulates neurotransmitters like serotonin, which regulates your mood and behaviour.
• Studies have shown that gut dysbiosis, a disruption in the gut microbiota, has been linked to conditions like anxiety and depressive-like behaviours.
• Foods that boost your gut microbiome, such as probiotics (fermented foods like yoghurt and kefir) and prebiotics (fibre-rich foods), also have a positive impact on your brain. 

Impact on Mental Health

Have you ever wondered how the food you eat can shape your mood and thoughts? The connection between your gut and brain means that every bite you take has the potential to impact your mental health. Here’s how:

• Research has shown that imbalances in your gut microbiota can cause conditions such as anxiety and depression. In recent research, faecal samples from depressed humans were transplanted into rats, which caused depressive behaviour in them. These faecal samples lacked a gut bacteria called coprococcus, indicating that it may have a causative relationship with depression.
• Your gut can produce small quantities of cortisol (stress hormone), which can cause irritability or depression. Cortisol can affect the gut microbiome by disrupting the balance of good and harmful microbes in your gut and altering gut permeability, which allows harmful substances and bacteria from the intestines to enter your bloodstream, leading to inflammation.

Read more - Tips To Boost Your Gut Microbiome.

Signs Your Gut Health May Be Affecting Your Mental State

When you eat something, it doesn’t just affect your digestion; it influences your immunity, mood, energy levels, and even your emotions. Here’s how your gut impacts your physical and mental well-being:

1. Digestive Symptoms:

• You may experience symptoms like abdominal bloating, gas, or discomfort, which indicates an imbalance in your gut microbiome. This can affect your mood and lead to irritability and stress.

2. Cognitive Symptoms:

• Poor gut health can lead to difficulties in thinking, remembering, and making decisions, such as brain fog.

3. Emotional Symptoms:

• If you face anxiety, irritability or depression without a clear cause, it can be a result of gut health-related issues.

How to Support the Gut-Brain Axis

We have seen how your gut health affects your brain, and mental health impacts your gut. So, how can we support this gut-brain axis? It comes down to two key approaches:

• Promoting gut health.
• Promoting mental well-being.

Here are some practical tips to support your gut-brain axis:

• Eat a healthy and well-balanced diet. Include diverse foods like fresh fruits and vegetables, whole grains, lean meats, nuts, seeds and healthy fats like eggs and fish. Include probiotics like yoghurt, kefir, fermented vegetables, and high-fibre foods to support a healthy gut microbiome.
• Stay hydrated by drinking plenty of fluids. Your body requires water for all its functions, including digestion. It also helps maintain a healthy and diverse gut microbiome and prevent digestion-related issues like constipation.
• Limit your intake of processed and highly refined foods. Such foods contain less nutrients and fibre, making it a not-so-healthy option. Also, cut out sugary foods like desserts and beverages, as excess sugar promotes the growth of harmful bacteria in your gut, which outgrows the healthy ones and throws your gut microbiome off-balance.
• Practise stress-relieving techniques to keep your mind calm and clear. Physical exercises like jogging, swimming, or cycling, yoga, meditation, breathing exercises, and mindfulness can help you manage stress and anxiety. Engaging in your hobbies or other activities that you enjoy is also beneficial for your mental health.

Wrapping Up

Your gut is rightly called the second brain because of its importance in impacting both your mental and physical well-being. 

Why should you be aware of the gut-brain axis? It highlights why gut health is important for your mental well-being and why managing stress and mental health issues is crucial for gut health. 

Maintaining a healthy gut microbiome through dietary and lifestyle changes and managing stress can help support your gut-brain axis and keep you healthy physically, mentally and emotionally.