For thousands of years, traditional medicine has claimed gut health is the foundation of all health.
As the research slowly catches up, increasing evidence shows that digestive health is intricately connected to the healthy function of all physical systems – especially when it comes to mental health and immunity.
The Role of Bacteria in Gut Health
Our body is home to trillions of bacteria, viruses, fungi, and other microbes – collectively known as the microbiome. The balance and diversity of these bacteria are crucial for maintaining and regulating immune, heart, mental and digestive health.
The majority of these microbes reside in the intestinal tract, making up the gut microbiome.
Gut microbiota plays a pivotal role in:
- Aiding the digestive process
- Breaking down toxic food
- Absorbing key nutrients and minerals
- Maintaining the structural integrity of the gut mucosal barrier
Gut health largely depends on a balanced co-existence of healthy and unhealthy (or pathogenic) bacteria and a wide range of bacteria diversity. When this balance is disturbed, it throws the gut and the rest of the body out of homeostasis.
Gut Dysbiosis: A Disturbance in the Force
A disturbed balance of gut bacteria is called ‘gut dysbiosis’. This can be caused by certain diets, infectious illnesses, and prolonged use of antibiotics or medications that likewise impact the microbiome.
Gut dysbiosis disturbs immune function and contributes to increased permeability of the intestinal barrier (what many call ‘leaky gut’), ultimately driving systemic inflammation. Gut dysbiosis is associated with weight gain, high cholesterol, and high blood sugar. It also can lead to the development and exasperation of inflammatory diseases and gastro-disorders.
Studies link gut dysbiosis to an increased risk of developing:
- Crohn’s disease
- Ulcerative colitis
- Irritable bowel syndrome (IBS)
Why is gut health important for immune health?
The microbiome plays a critical role in shaping and training our innate and adaptive immune systems.
With roughly 70-80% of our immune cells residing in the gut, there is a delicate interaction between gut microbiota, our intestinal lining, and the mucosal immune system. The immune system and gut microbiota engage in bidirectional communication, with gut bacteria not only ‘educating’ immune cells, but also producing metabolites that are vital in activating or soothing our immune response.
Mucosal Barrier Function
A single layer of thin tissue separates the intestinal lumen (the tunnel of the intestine) from the underlying tissues.
Many mechanisms are devoted to maintaining the integrity of this barrier, which blocks food antigens, toxins, and pathogenic (disease-causing) bacteria from entering the rest of the body. This is called mucosal barrier function, and the breakdown of this function can lead to systemic inflammation, aberrant immune responses, and mucosal tissue damage. Some call this condition ‘Leaky Gut’, although this is not a term used often by medical professionals.
Current research has linked the disruption of the mucosal barrier integrity to the development and worsening of IBD, as well as a number of other conditions.
Mucosal Healing & Homeostasis
One of the ways the body maintains the integrity of the mucosal barrier is through binding molecules produced by the microbiome.
For example, Short Chain Fatty Acids and AhR ligands metabolized from certain food or herbal compounds have been found to activate pathways that act directly to modulate immunity, regenerate mucosal barrier function, and maintain gut bacteria balance.
The AhR pathway has actually become a new target for IBD therapies and is the main mechanism through which the herbal compound Qing Dai (QD) induces remission in UC patients.
Qing Dai (QD) contains the Indole alkaloid which is metabolized into a binding molecule that activates the AhR pathway, signaling the upregulation of anti-inflammatory cytokines (such as IL-22) that contribute to mucosal healing. In fact, QD is the first IBD therapy found to induce remission through this pathway.
Gut Health & Mental Health
Research has revealed bidirectional communication between the gut, the nervous system, the brain, and mental health. This complex network is referred to as the ‘brain-gut axis’.
The brain-gut axis involves the vagus nerve, both the sympathetic and parasympathetic nervous systems, certain gut hormones, cytokines, and the intestinal microbiome.
Gut Health & The Nervous System
The nervous system is comprised of two main components:
- The central nervous system (CNS), made up of the brain and the spinal cord.
- The peripheral nervous system (PNS), made up of the nerves branching from the spinal cord and extending throughout the body.
The enteric nervous system (ENS) makes up the largest and most complex part of the PNS. It’s main role is controlling digestion, and modulating immune and endocrine functions, motor functions, blood flow, and mucosal secretions.
This network of nerves, sensory neurons, and neurotransmitters runs along the walls of the GI tract, extending from the esophagus through the stomach and intestines to the rectum.
Accompanying the enteric neurons embedded in the gut are cells called ‘enteric glia’ that assist the ENS in maintaining the integrity of the epithelium barrier (an important part of the intestinal mucosal barrier), playing a role in intestinal inflammation and microbiome interaction.
GI Conditions linked to the ENS:
- Irritable Bowel Syndrome
- Crohn’s Disease & Ulcerative Colitis
- Reflux & Acid Reflux
So, how does the enteric nervous system affect mental health?
Researchers believe that disturbances in the gastrointestinal system may send signals to the central nervous system via the gut-brain axis that eventuate in mood changes.
One such possible mechanism was recently found in a study on peptidoglycan, which is part of a bacterial cell membrane and a “major gut microbial signal”. The researchers found that when peptidoglycan translocates to the blood through a dysfunctional gut barrier wall, it preferentially moves on to the brain, whereas this selective migration to the brain does not happen if the peptidoglycan is injected directly into the bloodstream.
The mounting evidence that gut health impacts mental health and mood explains the large amount of IBS and IBD patients who also suffer from depression and anxiety.
Neurotransmitters & Gut Microbes
Gut microbiota play a pivotal role in the production and supply of our most important mood-regulating neurotransmitters: GABA, serotonin, and dopamine.
Roughly 95% of the body’s serotonin is produced by gut bacteria. Basically, certain gut microbes convert the diet-derived amino acid, tryptophan, into serotonin. Serotonin acts as both a hormone and a neurotransmitter and is crucial in regulating our mood, cortisol levels, digestion, bone health, sexual health, and sleep cycles.
Disturbed gut function can therefore lead to an imbalance of serotonin, which is implicated in various mental health conditions, including depression, anxiety disorders, obsessive-compulsive disorder, and PTSD.
Roughly 50% of the body’s dopamine is also produced in the gut. While serotonin is viewed as the ‘happy and content’ hormone, dopamine is our ‘motivation’ hormone, connecting feelings of pleasure to certain behaviors the body deems beneficial. These include eating, sex, spending time with loved ones, and enjoying music and the arts.
There’s a dark side to this reward system, though. Dopamine is heavily implicated in the development of addiction to drugs, alcohol, video games, gambling, and social media – especially TikTok, which some call “Digital Crack Cocaine.”
These activities can raise dopamine levels beyond the healthy amount, causing a depletion that leads to low moods, exhaustion, lack of concentration, moodiness, anxiety, depression, low sex drive, and a lack of pleasure from experiences that are usually enjoyable.
Gamma-aminobutyric acid (GABA)
Gamma-aminobutyric acid (GABA) is perhaps one of the most important neurotransmitters for mental health as it plays a key role in inhibiting stress signals and calming the nervous system.
It does so by decreasing the stimulation of neurons so that certain excitatory signals aren’t passed along to other neurons. By blocking signals related to anxiety, fear, and stress, GABA helps slow down the brain, calm the body before sleep, and improve sleep quality.
Lower or fluctuating levels of GABA have been associated with anxiety disorders, schizophrenia, autism spectrum disorder, and major depression.
For those with mild anxiety, it may be helpful to know that there are many foods, herbs, and natural supplements that boost GABA production, making them promising alternative treatments for anxiety. Many of these have been used for thousands of years to soothe ‘nerves’, especially ashwagandha, chamomile, St John’s wort, and valerian.
The Main Causes of Poor Gut Health
The main causes of poor gut health include:
- Prolonged stress
- Cigarette smoking
- A lack of diversity in one’s diet
- Highly processed foods and sugars
- Excessive alcohol consumption
- Poor sleep quality, or lack of sleep
- Antibiotics and certain medications
The Risks of Poor Gut Health
The evidence suggests that gut health does not stand alone, but is intricately tied to the health of all other physical systems. Firstly, dysbiosis (an imbalance of good and bad gut bacteria) has been linked to Crohn’s disease and ulcerative colitis, as well as numerous other autoimmune diseases.
Other conditions linked to poor gut health include:
- Weight gain
- Multiple sclerosis
- Cancer growth
- Rheumatoid arthritis
- Anxiety and depression
- Skin conditions (dermatitis, psoriasis, acne, and rosacea.
Signs of an Unhealthy Gut
One of the clearest signs of an unhealthy gut is an upset stomach. Frequent symptoms such as abdominal discomfort, bloating, diarrhea, heartburn, and gas all indicate issues with the digestive system.
That said, a disturbance in the gut can manifest elsewhere. Signs to watch out for include:
- Trouble sleeping
- Food intolerance
- Extreme food cravings (watch out for sugar)
- Extreme weight gain or weight loss
- Skin irritations
- Mood swings
How to Support Your Gut Health
The best way to support gut health is to work on restoring a healthy balance of gut bacteria through diet, which has the most significant role in the composition of the microbiome.
- Eliminate processed foods from your diet as much as possible
- Limit alcohol intake as much as possible
- Include more seasonal fruits and vegetables for more diversity
- Include more plant-based and home-cooked foods into your diet
- Include more fermented foods that help break down nutrients and ease digestion
Movement, staying hydrated and stress relief have also been found to improve gut health and digestive function.
Another fun way to improve gut health is to go outside and get your hands in the soil. Contact with soil (and its microbiome) is beneficial to the health of our gut microbiota. Interestingly, getting your hands in the soil also stirs up bacteria that, when inhaled, stimulate serotonin production.
Getting into nature and spending time with animals appears to be just as beneficial. A research team in Finland found that children from rural areas with exposure to nature and animals had a more diverse range of bacteria on their skin, fewer allergies, and stronger immune systems.
Essentially, the more in tune we are with nature, the happier and healthier our gut microbiome becomes.