We tend to think of our guts, if we think of them at all, as nothing more than a tube for transforming food into poop.
Even though we still have much to learn about the intricate world of intestinal microbiota and their influence on our health, treatment paradigms are being overturned as we realize the scope and depth of the relationship between the gut and the brain.
When we suffer from poor digestive health, it’s impossible not to pay attention to our guts. Between the pain, embarrassment and inconvenience of diarrhea, constipation, bloating, flatulence and cramping, and carefully avoiding foods that we once enjoyed, our guts take over our lives when we are not well.
From cardiac health to weight management, diabetes to premature aging, cancer to autoimmune disorders, our experience of health or disease is largely determined by the state of our gut. And our mental health is no exception.
Cutting edge research is finding that the gut communicates with the brain and has a powerful influence over both the physical condition of the brain and our cognitive function.
In order to understand the connection between our guts and our brains, we must understand the microbiome.
There are billions upon billions of tiny organisms living inside of each and every one of us, creatures that make their homes inside our bodies and consume our food to meet their nutritional needs. These microscopic squatters have a tremendous influence on our day to day wellbeing and are, in fact, intricately connected to our long term health because they’ve evolved to manipulate our thoughts and behavior in order to ensure their own survival.
The microbiome consists of trillions of microscopic creatures of thousands of different species. The majority are bacteria, but there are also some fungi, parasites and viruses.
When this community is composed of the right balance of microbials, they support healthy metabolism, immune function, digestion, hormone production and cognition. But when beneficial species exist in low numbers or are completely missing, opportunistic pathogens take over. In this case, the microbiome still has a powerful influence over many of our bodily systems, except now it has a detrimental effect on our health and wellbeing. Maintaining a diverse population of microbial species along with appropriate proportions of specific species within that community is the key.
We still have much to learn about the microbiome and its implications for our health, but the wait may not be long. Funding for such research shows how important the potentials in this field could be. In 2015 the US National Institute of Health awarded one million dollars to a research program intended to reveal the relationship between the microbiome and the brain. Meanwhile, ongoing breakthroughs are challenging our understanding of nutrition, immune response and the nervous system. We’re also having to reconsider everything we thought we knew about memory, cognition and mental health.
The microbiome exerts a tremendous influence over our brains and behavior. Fascinating research has recently revealed direct correlations between the species at home in our guts and the personality traits that we exhibit. Specific links were established, for instance:
• An abundance of gammaproteobacteria were found in people who exhibit high neuroticism.
• High levels of proteobacteria were found in people who displayed low conscientiousness.
• High levels of lachnospiraceae and other butyrate producing bacteria were found in people with high conscientiousness.
The microbiome communicates with the brain via three principal pathways:
Electrical Stimulation of the Vagus Nerve
The vagus nerve is the main component of the parasympathetic nervous system. It is the longest nerve, running from the brainstem all the way to the colon. It acts on all of the organs of the digestive tract, as well as the heart and lungs, and regulates involuntary bodily processes like heart rate, breathing and peristalsis.
We once thought the primary function of the vagus nerve was to carry motor commands from the brain to the organs, but scientists have discovered that a shocking 90% of the fibers in the vagus nerve are actually dedicated to relaying information from the gut to the brain.
On the other hand, when the messages from the body to the brain indicate that we are safe, the brain instigates the parasympathetic response. Activating the parasympathetic nervous system initiates the “rest and digest” mode and gives our bodies a chance to focus on nutrient allocation, tissue repair and detoxification while there is no immediate threat to our wellbeing.
Scientists believe that the most important function of the vagus nerve is carrying information about the organs to the brain and have concluded that our digestive tract, which is our largest surface that interacts with the outer world, could be considered an especially important sensory organ. The gut bacteria of our microbiome directly stimulate the vagus nerve, influencing our moods, memory and cognition.
Production of Neurotransmitters
Serotonin: Known is the “feel good hormone,” it acts as both a hormone and a neurotransmitter and governs feelings of wellbeing, contentment, satiety, anxiety and fear.
We use to think that serotonin was produced in the brain, but recent research has found that 90% of our serotonin is actually produced in our gut.
Alterations in serotonin levels are associated with moodiness, depression, anxiety and autism.
Dopamine: It is a neurotransmitter that is associated with feelings of euphoria, bliss, motivation and concentration. Our brains release dopamine when we experience pleasure. It also contributes to essential bodily functions including movement, sleep, learning, mood, memory and attention.
Half of the dopamine that we require to be well is produced in our guts.
Low dopamine is associated with lack of focus, fatigue, mood swings, poor sleep, low energy and loss of sex drive. It also correlates to mental health conditions including anxiety, depression, schizophrenia and Parkinson’s.
GABA: Gamma-Aminobutyric Acid, better known as GABA, is produced or consumed by multiple species of intestinal bacteria.
GABA is the body’s principal inhibitory neurotransmitter. It slows brain activity, which increases relaxation, reduces stress, calms nerves, balances mood, soothes pain and improves quality of sleep.
It promotes intestinal motility, reduces inflammation and enhances immune function. Low levels of GABA are linked to depression and mood disorders.
Short Chain Fatty Acids (SCFAs): They are the product of fermentation of dietary fibers by bacteria in our guts. SCFAs nourish the cells that make up the wall of the intestine, boost the protective capacity of our intestinal wall lining and support healthy digestive motility. SCFAs are also powerful anti-inflammatory agents.
The most famous of the short chain fatty acids produced by the gut is butyrate. It is especially effective at reducing inflammation – not just in the gut, but in the brain as well. Groundbreaking treatments are using butyrate to treat neurodegenerative diseases, depression and cognitive impairment.
Butyrate produced by bacteria in our guts enters our blood stream and crosses the blood-brain barrier, where it facilitates production of Brain Derived Neurotrophic Factor (BDNF). BDNF supports our ability to learn, remember and form new memories. It is regarded as “fertilizer for the brain” because of the way it enhances our neuroplasticity. Loss of neuroplasticity causes the trademark mental decline associated with Alzheimer’s and dementia.
Modulation of Immune Response
The final known pathway that our gut bacteria use to influence the brain is through the immune system. Our microbiome signals vital functions of our immune response that are essential to maintaining homeostasis. It influences both inflammation and our immune response by controlling what gets absorbed from our digestive tract to our bloodstream and what gets excreted.
When the immune system is overstimulated we develop chronic inflammation. Inflammation in the intestines causes the junctions in the cell walls to become more porous which leads to Leaky Gut. Food particles, bacteria and toxins are then able to enter the bloodstream, causing bodywide inflammation.
Some digestive bacteria produce Lipopolysaccharide (LPS). LPS is inflammatory and toxic. It can enter our bloodstream when our gut is hyperpermeable. Leaky Gut causes “leaky brain.” As the intestinal wall becomes more permeable, the blood-brain barrier weakens, leading to inflammation in the brain that influences the way we think and feel. Brain inflammation plays a role in depression, anxiety, brain fog and autoimmune brain disorders.
Psychologists are now treating depression by prescribing anti-inflammatory diets. In fact, many conventional therapies for mental disorders and neurological diseases are being revamped as experts uncover the intricate relationship between the microbiome and mental health.
A healthy gut is indispensable to a happy mind. The conclusion of a recent study from the Chinese Academy of Sciences aptly describes the shift that is taking place in the treatment of mental disorders:
“Mental disorders and neurological diseases are becoming a rapidly increasing medical burden. Although extensive studies have been conducted, the progress in developing effective therapies for these diseases has still been slow. The current dilemma reminds us that the human being is
a superorganism. Only when we take the human self and its partner microbiota into consideration at the same time, can we better understand these diseases.”
We are susceptible to many threats that can diminish the diversity of our microbiome. Remember how the composition of each of our microbiomes is unique? The baseline microbial species we start with are determined by our birth and early childhood experiences. However, most of us don’t keep all of them. Throughout our lives many things can happen which deplete our microbiomes and leave us vulnerable to pathogenic infections:
• Antibiotic overuse
• Inflammatory diet
• Lack of dietary fiber
• Chronic stress
• Traumatic experiences, especially in childhood
• High alcohol consumption
• Exposure to environmental toxins
• Pathogenic infections
• Nutrient deficiencies
• Insufficient sleep
IMBALANCE in the microbiome creates stress in the body that not only triggers inflammation but can also lead to significant mental health problems. Recent research at Stanford University revealed that even short-term digestive problems can contribute to mental health issues later in life.
A healthy gut supports a healthy mind. Scientists at Pacific Northwest National Laboratory have demonstrated that boosted levels of Lactobacillus are directly linked to enhanced memory. Higher levels of GABA, which of course, is produced by some species of gut bacteria, are also associated with better memory.
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