What really determines our mood and controls stress? Did you know that the secret may not lie in the head, but in the gut? The gut, called the "second brain", is home to a vast network of neurons and a vibrant community of microorganisms whose activity affects the gut and the whole body, and therefore the brain. This intricate connection affects everything from our emotions to our immune system. In this article, you'll learn why the gut is called the second brain and how taking care of it can be the key to better mental and physical health.
Historical origins
The concept of the gut functioning as a second brain has deep historical roots, particularly in Asian cultures. For example, traditional Chinese medicine has long considered the gut to be central to physical and emotional health. The gut, often referred to as the "center" or "lower dantian" (丹田), is considered a center of vital energy that is integral to overall well-being. This ancient view is based on the belief that the intestines play a key role in maintaining balance and harmony in the body, affecting both physical health and emotional stability.
In Indian Ayurvedic medicine, the digestive system is considered the cornerstone of health. The concept of "agni" or digestive fire is paramount and a healthy gut is considered essential for processing nutrients and maintaining vitality. These traditions have been aware of the intricate connections between the gut, mind and overall health long before modern science began to address these relationships.
Why is the gut called the second brain?
In the last few years and decades, scientists have increasingly focused on gut research. When we say that the gut is a second brain, we are referring to the enteric nervous system (ENS). This is a network of nerves in our digestive system that is able to work independently of the brain and spinal cord.
The ENS controls various functions such as digestion, enzyme secretion and blood flow, and is connected to the central nervous system (CNS) via the vagus nerve. The enteric nerve network is extensive and consists of interconnected nerve bundles in the intestinal wall and contains more than 100,000,000 neurons - more than in the spinal cord. The system, like the brain, uses about 30 bioactive chemicals to transmit information between cells, and 80% of the body's serotonin is produced in the gut. Serotonin is one of the chemical mediators through which nerve cells communicate with each other; it serves as a transmitter in the interaction between the gut and the brain and regulates gut motility. The gut and the central nervous system therefore have a similar structure and function and are in constant interaction.
Scientists are discovering surprising connections between the digestive system, the brain and our overall health, especially mental well-being. One of the interesting questions they are exploring is, "Where is stress born? In the head or in the gut?" The answer seems to lie in the complex interplay between the brain and the gut, often referred to as the gut-brain axis.
Understanding the gut-brain axis
The brain-gut axis is a complex two-way communication network that connects the central nervous system (CNS), including the brain and spinal cord, to the enteric nervous system (ENS) of the gastrointestinal tract. As we have already mentioned, this connection provides constant interaction and feedback between the brain and the gut, affecting both physical and mental health.
The main parts of the brain-gut axis
- Central Nervous System (CNS): The central nervous system (CNS), which consists of the brain and spinal cord, processes and integrates information from throughout the body and coordinates responses. It plays a key role in regulating mood, cognition, and emotional responses.
- Enteric Nervous System (ENS): The ENS, often referred to as the "second brain", is a vast network of neurons located in the walls of the digestive tract. It controls digestive processes such as peristalsis, enzyme secretion and blood flow. The ENS can function independently of the CNS, but is in constant interaction with it.
- Vagus nerve: The vagus nerve is the most important part of the parasympathetic nervous system and serves as the main communication pathway between the gut and the brain. It transmits sensory information from the gut to the brain and motor signals from the brain to the gut, thereby influencing digestive processes and emotional state.
- Neurotransmitters and hormones: The gut and the brain interact through various neurotransmitters and hormones. Other important chemicals involved in the brain-gut axis include dopamine, noradrenaline and gamma-aminobutyric acid (GABA).
- Gut microbiota: The trillions of microorganisms living in the gut, known as the gut microbiota, play an important role in the brain-gut axis. These microorganisms produce metabolites that can influence brain function and behaviour. They also affect the immune system and help maintain the integrity of the intestinal barrier.
- Immune system: Gut-associated lymphoid tissue (GALT) is an important part of the immune system, which is located in the gut. It interacts with the gut microbiota and the CNS and plays a role in the body's response to stress and inflammation.
Axis function
The gut-brain axis regulates a variety of functions and has a significant impact on health:
- Mental health: the gut-brain axis influences mental conditions such as anxiety, depression and stress. Changes in gut microbiota composition have been linked to mood disorders, suggesting that gut health may influence emotional well-being.
- Stress response: The gut microbiota may influence the production of stress hormones such as cortisol, thereby affecting the way the body copes with stress.
- Immune function: The brain-gut axis plays a role in regulating the immune system. An imbalance of the gut microbiota can lead to chronic inflammation, which is associated with a number of health conditions including autoimmune disorders and mental disorders.
- Digestive tract health: The ENS controls digestion, including the movement of food through the gut, the secretion of digestive enzymes and the absorption of nutrients. Dysregulation of the brain-gut axis can lead to digestive disorders such as irritable bowel syndrome (IBS) and other functional bowel diseases.
How does the gut-brain axis affect irritable bowel syndrome and what is the vicious circle in IBS?
Irritable bowel syndrome (IBS) is an example of the intricate relationship between the gut and the brain. People with irritable bowel syndrome have symptoms such as abdominal pain, bloating, diarrhea and constipation.
In irritable bowel syndrome, there are often communication problems between the gut-brain axis. Stress and anxiety, which are controlled by the brain, can exacerbate IBS symptoms by sending signals that cause the gut to be overly sensitive and reactive. Imbalances in the gut microbiota, which affect digestion and the gut's response to stress, also contribute to IBS. The production of serotonin, a key neurotransmitter produced in the gut, can be disrupted in IBS, leading to changes in gut function and sensitivity.
This creates a vicious cycle: stress and anxiety increase IBS symptoms, and discomfort from these symptoms increases stress and anxiety. In addition, stress can alter the gut microbiota and lead to dysbiosis, worsening IBS symptoms, and unhealthy gut microbiota can send anxiety signals to the brain, increasing stress.
How to break the vicious circle
A holistic approach to gut health involves more than just therapy. It involves dietary changes, such as following a low-FODMAP diet to avoid foods that trigger irritable bowel. Regular exercise, quality sleep and adsorbents such as Enterosgel probiotics (beneficial bacteria) can also improve gut health. Combining these approaches can address both the physical and psychological aspects of bowel disorders.
Given the close connection between the gut and the brain, a holistic approach to treating gastrointestinal (GI) disorders such as IBS is essential. Psychotherapy, particularly cognitive behavioural therapy (CBT), has been shown to be effective in managing the symptoms of IBS. Cognitive-behavioural therapy helps patients develop coping strategies to manage stress and anxiety, break the vicious cycle and address the psychological aspects of the disease.
Mindfulness Based Stress Reduction (MBSR) and gut-focused hypnotherapy are also used. MBSR involves meditation and mindfulness techniques to reduce stress, while bowel-focused hypnotherapy uses relaxation techniques to improve bowel function and reduce symptoms.
Understanding that the gut is a second brain therefore highlights the need for an integrated approach to health. Awareness of the connection between the gut and the mind can lead to improved treatment and quality of life for people with conditions such as IBS.