As often as we talk about “gut instincts” and “gut feelings,” we shouldn’t be surprised to learn there is a substantial connection between our gut and our cognitive and emotional health. This connection is called the gut-brain axis. It is a complex system that oversees communication between the gut and the brain.
How does your gut affect your brain? Your gut affects your brain by contributing to hormones and neurotransmitters in the body, impacting mood and behavior. All of this occurs through an intricate series of interactions. Don’t worry — we’ll walk you through it.
Your 2 Brains
Chances are you already know about your first brain. Comprised of around 100 billion neurons and even more glial cells, this is the head of your central nervous system or CNS. The spinal cord is the other half of your CNS.
Your second brain is the enteric nervous system, or ENS. This system is known as the “brain in the gut” due to its 200-600 million neurons. (For reference, the number of nerve cells in the ENS equals the number of nerve cells in the spinal cord.)
The network of neurons in the ENS extends from the esophagus to the rectum and controls the gastrointestinal tract or GI tract. It can do this independently of the CNS, sensing stimuli and responding accordingly all on its own.
When the ENS and CNS need to communicate, they do so mainly through the vagus nerve. This single nerve starts in the brain stem, extends through the neck and thorax, and finishes in the abdomen, making it the body’s longest cranial nerve.
The vagus nerve is a key component of the autonomic nervous system and the parasympathetic nervous system. The parasympathetic nervous system is in charge of resting and relaxation. The autonomic nervous system is part of the ENS. It impacts functions such as:
- Heart rate
- Blood flow and vasomotor activity
- Digestive reflexes (such as swallowing and vomiting)
- Respiratory reflexes (such as coughing and sneezing)
Although the ENS can operate independently of the CNS and vice versa, these two systems typically communicate bi-directionally. They work together to maintain a functional digestive system. The bi-directionality of this communication network has interesting implications for mental health, but more on this later.
How Your Microbiome Helps
Your gut is full of trillions of live bacteria. Most of these microbes are good. They help produce neurotransmitters that influence mood and cognitive function. They also produce microbial metabolites and other byproducts like short-chain fatty acids (SCFAs) that impact your metabolism and immune system.
Here are some other ways healthy gut microbes help us:
- They absorb nutrients and digest food
- They help synthesize vitamins
- They reduce inflammation and promote homeostasis
The gut microbiome is a diverse ecosystem of microorganisms that thrives in a delicate balance. When that ecosystem becomes imbalanced, we can end up with microbial dysbiosis. Dysbiosis is linked to a wide range of conditions, including:
- Inflammatory bowel disease (IBD)
- Irritable bowel syndrome (IBS)
- Crohn’s disease
- Rheumatoid arthritis
- Type 2 diabetes
- Alzheimer’s disease
- Parkinson’s disease
Gut microbiome health has also been linked to brain function and mental health. Conversely, mental well-being factors, such as psychological stress, can have negative repercussions on gastrointestinal microbiota.
Fortunately, there are plenty of natural ways to help maintain a healthy gut and even heal an unhealthy gut. We’ll cover some of these later on.
Neurotransmitters are chemicals that help regulate numerous bodily functions. Imbalances in neurotransmitter levels have been associated with neurological disorders like depression.
You’re probably already familiar with some neurotransmitters, like serotonin and dopamine. Serotonin is largely associated with mood and happiness. But did you know that serotonin, dopamine, and several other neurotransmitters are produced in your gut?
Here are some of the big ones:
- Serotonin: regulates behavior, mood, and memory. The gut produces up to 95% of the body’s serotonin.
- Dopamine: regulates motor functions, motivation, and emotion. The gut produces about 50% of the body’s dopamine.
- Norepinepherine: also called noradrenaline. Norepinephrine helps regulate attention, learning, motivation, arousal, and reward.
- GABA (gamma-aminobutyric acid): inhibits the central nervous system. GABA can help reduce anxiety and produce a calming effect.
Our bodies regulate hormones through our endocrine systems. Hormones impact our growth, sexual function, and mood, as well as help us regulate appetite. It turns out this is another two-way street. Having certain bacteria in our gut microbiota can impact hormone release in the gut.
Some of the hormones influenced by our gut bacteria include:
- Leptin: responsible for satiety. Leptin helps balance our intake and output of energy. It also impacts appetite and metabolism.
- Ghrelin: responsible for hunger. Ghrelin stimulates our bodies to eat, store fat, and release human growth hormone.
- Glucagon-like peptide 1 (GLP-1): responsible for insulin secretion. Low levels of GLP-1 may lead to obesity. High levels of GLP-1 may contribute to certain types of hypoglycemia.
- Insulin: responsible for regulating blood glucose levels. Insulin resistance can lead to obesity and diabetes.
It’s a Two-Way Street: Mental Health Can Alter Digestion
Mental health disorders and digestive issues often go hand-in-hand. Those dealing with irritable bowel syndrome, for instance, are significantly more likely to experience symptoms of depression or anxiety.
Here are some of the symptoms that stress can cause:
- Abdominal pain
Initially, the body’s stress response is adaptive. It helps us deal with threats and trauma. This response, however, is intended to be short-term. While normally helpful, the stress response becomes unhealthy when stress is frequent or consistent over extendedperiods (chronic stress).
Chronic stress is a major cause of both mental and physical problems. It is linked to anxiety and depression and disrupts homeostasis, leading to a variety of gastrointestinal disorders. In fact, the effects of prolonged stress in the body are connected to 80% of health disorders, including physical, neurological, and psychological.
That’s not all. The neurological pathways activated in response to physical pain overlap heavily with the pathways activated in response to social or emotional pain. This suggests that physical and psychological stress may produce similar physiological responses.
Perhaps this is a factor in the two-way street between stress and digestive issues. Fortunately, it also means that there may be treatment options for any one condition than traditionally thought.
Can behavioral treatment help with GI disorders?
Behavioral treatments such as cognitive behavioral therapy (CBT) are generally associated with mental health. However, recent research shows that CBT can help reduce symptoms of IBS. In fact, implications for behavioral treatment of gastrointestinal disorders have led to an entirely new field of medicine called behavioral gastroenterology.
Behavioral gastroenterology explores psychological and lifestyle factors that may impact digestive health. Treatment options may include CBT, hypnotherapy, and meditation, as well as dietary and other lifestyle changes.
Dietary modification plays a major role in treating GI disorders. With dysbiosis so heavily linked to illnesses, following a dysbiosis diet may significantly improve gastrointestinal health. This may include removing foods that contribute to dysbiosis and adding gut-healing foods, probiotics, and prebiotics.
Steps You Can Take
Whether you want to prevent gastrointestinal issues or reverse them, here are a few steps you can take to get started:
- Get into a meditation practice. Remember that it is equally important to take care of your mental health as it is to take care of your physical health.
- Add psychobiotics to your diet. Psychobiotics are probiotics that positively affect mental health through your gut bacteria. These probiotics can be found in kefir, sauerkraut, kimchi, and miso. They are also available as supplements.
- Get your exercise. Regular exercise has been shown to positively impact IBS and psychological health.
- Vagus Nerve Stimulation. This Nerve connects the brain to the gut where it controls the rest and digest response of the nervous system. Massaging behind the ears, gargling, deep breathing exercises, and contrast cold/ hot water therapy has been shown to stimulate the vagus nerve.
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