When we think about mental health, our minds typically jump to the brain. However, emerging research is shedding light on a fascinating, little understood aspect of our nervous system: the enteric nervous system (ENS), often referred to as our “second brain.” If fact it should be referred to as the first brain, the neurons in the gut start to develop before those in our head. This complex network of neurons line the gastrointestinal tract and play a crucial role in our overall well-being, including our mental health. Yet, most people know little about it and have even less idea of its importance.
The Enteric Nervous System: Your Gut’s Hidden Brain
The enteric nervous system is a vast network of neurons embedded in the lining of your gastrointestinal tract, stretching from the oesophagus to the rectum. This “second brain” contains approximately 100 million neurons – more than in your spinal cord or peripheral nervous system. Despite its complexity and importance, the ENS remains a mystery to many.
Unlike the central nervous system (CNS), which consists of the brain and spinal cord, the ENS can function independently. It controls digestive processes like peristalsis, enzyme release, and blood flow in the intestines without input from the brain. This autonomous functioning is why you can still digest food even if the vagus nerve, the primary connection between your gut and brain, is severed.
The Gut-Brain Axis: A Two-Way Street
The connection between your gut and brain, known as the gut-brain axis, is bidirectional. This means that your brain can influence your gut function, and conversely, your gut can send signals that affect your brain function and mental state. You know that “gut feeling” it is more than we think.
The vagus nerve serves as the primary highway for this two-way communication. It transmits signals from the brain to the gut, controlling various digestive processes. More importantly, it also relays messages from the gut back to the brain, influencing mood, cognition, and even behaviour.
This gut-to-brain communication is where the enteric nervous system plays a crucial role. The ENS constantly monitors the state of the digestive system and sends this information to the brain via the vagus nerve. These messages can include information about:
1. Nutrient status
2. Presence of harmful bacteria or toxins
3. Inflammation levels
4. Gut hormone production
How Your Gut Influences Your Mind
The impact of these gut-derived messages on brain function and mental health is profound and multifaceted:
1. Neurotransmitter Production: Your gut produces a significant amount of neurotransmitters, including about 95% of your body’s serotonin, often called the “happiness hormone.” These neurotransmitters play crucial roles in regulating mood, sleep, appetite, and pain sensation.
2. Immune System Regulation: The gut houses about 70% of your immune system. Signals from the gut can influence inflammation levels throughout the body, including in the brain. Chronic inflammation has been linked to various mental health disorders, including depression and anxiety.
3. Stress Response: The gut communicates with the brain’s stress response system, influencing how we react to stressful situations. An unhealthy gut can lead to an overactive stress response, potentially contributing to anxiety disorders.
4. Cognitive Function: Emerging research suggests that gut health may influence cognitive functions like memory and learning. Some studies have even found associations between gut microbiome composition and conditions like Alzheimer’s disease.
You know that gut feeling, well it is more than you think, the ability to work in tandem with the brain has led to it being seen as the seat of intuition, when you feel good about something your decision making is more relaxed and likely to be more accurate.
Even when not consciously utilised, intuition often provides benefits in daily life. The common feeling of unease when contemplating a decision is a clear example of gut instinct at work.
The Role of Diet in Gut-Brain Communication
Given the importance of the gut in influencing brain function, it’s not surprising that what we eat can have a significant impact on our mental health. Here’s how diet affects this gut-brain communication:
1. Nutrient Absorption: The nutrients we absorb from our food provide the building blocks for neurotransmitters and support overall brain health. A diet lacking in essential nutrients can lead to suboptimal brain function.
2. Microbiome Health: Our gut microbiome, the trillions of bacteria living in our intestines, plays a crucial role in digesting food, producing certain vitamins, and even generating neurotransmitters. A diverse, healthy microbiome supported by a varied, fiber-rich diet can promote better mental health.
3. Inflammation: Certain foods, particularly those high in refined sugars and unhealthy fats, can promote inflammation in the gut. This inflammation can be communicated to the brain via the gut-brain axis, potentially contributing to mood disorders.
4. Gut Hormone Production: What we eat influences the production of various gut hormones that can affect mood and behaviour. For example, the hormone ghrelin, often called the “hunger hormone,” has been shown to have antidepressant effects.
The Impact of Modern Diets on Gut-Brain Communication
Unfortunately, many aspects of the modern Western diet can negatively impact this delicate gut-brain communication system:
1. Processed Foods: High in refined sugars and unhealthy fats, these foods can promote inflammation and negatively alter the gut microbiome.
2. Lack of Fibre: Many modern diets are deficient in fibre, which is crucial for maintaining a healthy gut microbiome. Fibre is what feeds the beneficial bacteria in the gut, modern diets have less than 50% of what an adult needs on a daily basis and in children it is even less.
3. Artificial Additives: Some food additives have been shown to negatively impact gut health, potentially disrupting gut-brain communication. The chemistry of the modern ultra-processed diet contains additives that are designed to keep you coming back for more, see my article on ultra-processed foods here.
4. Lack of Variety: A diet lacking in diverse plant foods can lead to a less diverse gut microbiome, which may impact mental health.
Supporting Mental Health Through Gut Health
Understanding the importance of the enteric nervous system and gut-brain communication opens up new avenues for supporting mental health. Here are some strategies:
1. Eat a Diverse, Plant-Rich Diet: This supports a healthy, diverse gut microbiome.
2. Include Fermented Foods: Foods like yogurt, kefir, and sauerkraut can support gut health.
3. Manage Stress: Chronic stress can negatively impact gut health. Practices like meditation or yoga may help.
4. Stay Hydrated: Proper hydration is crucial for maintaining a healthy gut lining.
5. Consider Pre and Probiotic Supplements: While more research is needed, some studies suggest a properly supported gut biome may help support mental health through their effects on the gut.
Final thoughts
The enteric nervous system and the gut-brain axis represent a frontier in our understanding of mental health. By recognizing the importance of this “second brain” in our gut, we can take a more holistic approach to mental well-being. While nutrition and gut health aren’t the only factors influencing mental health, they play a crucial role that has been overlooked for far too long.
As research in this field continues to evolve, one thing is clear: the health of our gut is inextricably linked to the health of our mind. By nurturing our enteric nervous system and supporting healthy gut-brain communication, we may be able to open new doors in the prevention and treatment of mental health disorders.
