Mmm...braaains. From the Top
Starting At The Top…
Grey Matter
Our brains - the most complex thing in the known universe(1)! There’s much mystery still surrounding the squishy grey stuff in our heads but here’s a few amazing facts that we do know -
- “...on average the human brain has 86bn neurons.”(2)
- Neurons (nerve cells). These specialised cells form the basic units of the brain and are designed to transmit information to other nerve cells, muscle, or gland cells. Information runs between them, processing everything we see, think, smell, hear or do. These neurons move information at different speeds, the fastest being at around 250 mph(2).
- Electrical + chemical messaging. When neurons receive or send messages, they transmit electrical impulses along their axons (a long single fiber which can range in length from a tiny fraction of an inch to about one meter or more) which are then received by the short fibers called dendrites (the tree branch-like structures) at the end of the cell. Structures between the cells called synapses allow messages to pass through cells and from cell to cell across the body. More about information/neurotransmission here.
- Energy-hungry brains. The massive number of neurons in the brain requires a lot of energy. It’s estimated that 20-25% of our total energy budget goes to running our brains alone(2).
- Neurons don’t regenerate. Like heart cells, neurons are post-mitotic. This means that they don’t go through cell division and they don’t regenerate unlike the other cells in our body. When we are born, we have more neurons than we will for the rest of our lives. We lose them all the time, even as you are reading this you’ll be losing them(3)!
- Neural connections. Each neuron may be connected to up to 10,000 other neurons, passing signals to each other via as many as 1,000 trillion synaptic connections(4). These neural connections are not static and change over time.
- Neuroplasticity. Although neurons don’t regenerate - they are designed to last a lifetime - neuroplasticity allows nerve cells to build new connections and our minds can wire and rewire themselves endlessly. This is how we can learn new skills, adapt to new situations and environments and change our thinking and behavioural patterns. We discuss the Neuroplastic Mind in depth and its relation to mental health and meditation in the Healing section.
- Brain + nervous system immune cells. Microglial cells are a type of macrophages that are found in the spinal cord and brain. They remove damaged neurons and infections and are important for maintaining the health of the central nervous system CNS.
Aren’t we special creatures! We could talk about brains for days but we’ll stop here as we want to get to the relevant bits.
Guts + Brains
Nerves, the Gut + the Brain - How it all Connects
The Gut-Brain or “Second Brain”
“Technically known as the enteric nervous system, the second brain consists of sheaths of neurons embedded in the walls of the long tube of our gut, or alimentary canal, which measures about nine meters end to end from the esophagus to the anus. The second brain contains some 100 million neurons, more than in either the spinal cord or the peripheral nervous system.”(4)
The enteric nervous system (ENS) or intrinsic nervous system is part of the autonomic nervous system which includes all of the nerves that branch out from the brain and spinal cord and extend to other parts of the body including muscles and organs. It is the control system that acts largely unconsciously to regulate bodily functions such as heart rate, digestion, respiratory rate, pupillary response etc. The ENS consists of a mesh-like system of neurons which governs the function of the gastrointestinal tract.
Governing the Messy Business of Digestion
The gut is lined with hundreds of millions of neurons which are in constant communication with the brain, yet can function independently from it. It’s likely we evolved this intricate web of nerves equipped with its own reflexes and senses, to perform the complex business of digestion and to expel waste "on site", without having to involve the brain - which should be free to ponder philosophy and how to survive - and cutting out the middleman (the spinal cord) also. So the messy and complex task of digestion is delegated to this neural network which is so extensive, it has been termed the “Gut-Brain” or “Second Brain’”. But it’s complexity and influence goes far beyond mere digestion and absorption(4).
“Trust Your Gut” - the Gut + Mental Wellbeing
The gut-brain axis appears to be bidirectional - the brain acts on GI and immune functions which help to shape the gut's microbial communities, and our gut microbes create neuroactive compounds - including neurotransmitters and metabolites - which impact the brain. Given the sheer size of the second brain and the fact that 90% of the information carried via the vagus nerve “highway” directly linking the gut with the brain, carries information directly from the gut to the brain (and not the other way round), you may not be surprised to learn that the gut can influence and inform our state of mind and emotions(5). The enteric nervous system (ENS) uses more than 30 neurotransmitters, just like the brain, and 95% of the body's serotonin and melatonin is found in the small and large intestines(4), (6). It’s likely you will have experienced this direct gut-brain connection before in the form of “butterflies” in the stomach or getting a “gut feeling”.
Little Love (Gut) Bugs
The gut’s microbiota inhabitants can also influence the health of both the gut and the brain, impacting mental clarity and affecting our emotions. Stress can alter our gut bacteria populations, which can in turn can influence our mood. It is widely recognised that depression and anxiety are influenced and governed by the health of our gut microbiota. Each of our unique gut microbiome populations and their interactions with our ENS, gut, brain and impact on our overall health is extensive(5).
Guts Health = Brain + Body Health
Gut Health = Full Body Health
It is emerging that mental health issues may involve both brains and that the ENS might play a role in numerous other diseases in the body also. Here are some of the main ways in which our guts can influence our overall health and wellbeing -
- “Outside the digestive tract, gut microbes influence other organs and tissues through neural networks and signaling molecules. Through these complex communication networks, gut microbes regulate 70 to 80 percent of the immune system…(and)...also modulate the function of the brain, bone, heart, skin, eyes, and muscle tissue.”(7)
- “When the gut microbiome is disrupted, processes normally regulated by the gut microbiota, such as immunity and brain function, are impaired. This ultimately may lead to the development of chronic conditions such as autoimmune disease, metabolic dysfunction, and mental health issues, among many other health problems.”(7)
- The trillions of bacteria in the gut "communicate" with enteric nervous system cells (which they greatly outnumber)(5) These microbial compounds communicate via the vagus nerve, which connects the brain and the digestive tract(8)
- Certain bacteria (both beneficial and pathogenic) have the ability to migrate to other organs within the body via the gut lining. Once there, they can trigger autoimmune disorders and other diseases(9)
- Beneficial bacteria stimulate the growth of the intestinal lining and the immune system of the intestine (Anatomy of the Digestive System)
- Gut microbes help to control leakage through both the intestinal lining and the blood-brain barrier, which would usually protect the brain from potentially harmful agents and the body against intestinal pathogens(8)
- Microbes in the gut contribute to host health through biosynthesis of vitamins and essential amino acids, as well as generation of important metabolic byproducts from dietary components left undigested by the small intestine (they breakdown the “leftover” food we can’t digest in our guts)
- Short chain fatty acid (SCFA) byproducts such as butyrate, and propionate (from dietary fiber) act as a major energy source for intestinal epithelial cells and may therefore strengthen the mucosal barrier and thus, improve immune system function(8)
- Though not currently well understood, (more research is underway to explore this) the second brain neural network mediates our immune response(5)
As you can see, the gut’s influence on the other systems of the body and overall health is profound. We explore this further in Nature + the Microbiome.
The Vagus Nerve + Leaky Brain
The Vagus Nerve
Wanderer
"Vagus" means “wanderer” in Latin, accurately representing how the nerve wanders all over the body and influencing the function of numerous internal organs. The vagus nerve plays a key part of your parasympathetic “rest and digest” nervous system, influencing breathing, digestive function and heart rate. Thus, it has a huge impact on your mental and physical health. Stimulating the vagus nerve can activate vagal tone and thus, the parasympathetic nervous system. Having higher vagal tone means that your body can relax faster after stress, while also provide other numerous health benefits, including improved digestion(8). We list a few ways to stimulate the vagus nerve on the Health-Hacks page.
Importance of the Brain, Gut + Vagus Nerve Connection
“90% of our brain’s output goes into something called the pontomedullary area, it’s the lower two-thirds of the brain stem, and that goes into the vagus, or the pneumogastric nerve, which innervates the digestive tract.”(3)
Brain > Vagus Nerve > Gut
The brain and vagus nerve and inextricably linked - when the brain isn’t functioning or firing optimally, (if its inflamed for example) this can lead to poor vagal activity, expressed by decreased pancreatic enzyme secretion, poor gallbladder function and poor overall gut function. This leads to decreased intestinal immune activity and intestinal blood flow and thus, an opportunity for an overgrowth of pathogenic bacteria and yeast arises(3). Vice-versa, when something dysfunctions with the gut, particularly in the case of leaky gut, this can create negative consequences throughout the rest of the body.
How the Brain Influences the Gut
The frontal cortex stimulates the vagal nuclei to activate gut motility (intestinal peristalsis), which moves the contents of our gut through the digestive tract and out the other end. It also stimulates enzyme secretion, digestive enzyme secretion, the release of hydrochloric acid (HCL) in the stomach and modulates blood flow to the gut. The brain primarily communicates with the gut via neuronal projections and also hormones which are secreted by the hypothalamus. In the gut, the main players are the ENS, the intestinal immune system, (the gut-associated lymphoid tissue and the gut flora), and then the intestinal microglia. Read about the Gut Immune System on the Nature + the Microbiome page.
Leaky Gut + Leaky Brain
As we discuss in length in the SIBO + Autoimmunity section, a pathogenic overgrowth of bacteria and/or yeast causes intestinal permeability or leaky gut, and leaky gut causes a state of chronic low grade inflammation. The increased permeability of the intestinal mucosa allows bacteria, bacterial toxins, potentially harmful microorganisms and small molecules to ‘leak’ into the bloodstream. The inflammatory response thus, can become systemic, travelling via cytokines and crossing the blood-brain barrier (BBB). Although one of the BBB’s primary functions is to separate the CNS from soluble inflammatory mediators and effector immune cells from peripheral circulation, when inflamed the BBB can also become ‘leaky’ and inflammation can occur in the brain as a result. So, leaky gut and systemic inflammation can lead to the BBB being compromised, which leads to an inflammation of the brain (aka Leaky Brain)(3), (9).
Why a “Leaky Brain” + Brain Inflammation is Bad
As we mull over here, any inflammation, especially chronic inflammation should be avoided as it’s hugely damaging.
Recognising the signs and symptoms of Leaky Brain (which we list below) can be tricky as many overlap with autoimmune systems. But be wary of them- this condition can lead to an increased risk of developing neurological or psychiatric conditions, as well as also being caused by them. It can also cause a host of other neurological diseases and complications which can be read about here.
Symptoms of Gut-Brain Axis Dysfunction
Read more about the gut-brain axis here
- Brain fog
- Fatigue
- Chronic digestive issues
- Progressive cognitive decline
- Memory loss
- Mental disorders - anxiety, depression, ADHD, autism spectrum disorder, behavioral problems
- Cold hands + feet
6 Causes of a Leaky Brain
The below listed causes all have one uniting factor - inflammation.
- Gut Dysbiosis/SIBO
- Leaky Gut
- Autoimmune Disease
- Mental Health Conditions
- Stress
- Vagus Nerve Dysfunction
Symptoms + Signs
A leaky brain can manifest in numerous ways(4) -
- ADD/ADHD/Autism spectrum disorders
- Brain fog or difficulty concentrating
- Chronic fatigue that does not improve with rest or sleep
- Headaches or migraines that come on suddenly become worse with standing, and grow more severe as the day progresses
- Memory loss or another cognitive decline which may lead to dementia and Alzheimer’s disease
- Mood disorders - anxiety, depression, and schizophrenia
- Peripheral neuropathy or muscular sclerosis
- Seizures
Reversing + Treating a Leaky Brain
Treating a leaky brain starts by healing a leaky gut which we provide help for on our Healing the Gut + Autoimmunity page.
There is a lot more to this which we won’t go into on this page, but you can read more here.