The Gut-Brain Axis: determining physical, mental health - Fit Grinds
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The Gut-Brain Axis: determining physical, mental health

Amending patients’ diet and lifestyle can help restore balance to the gut-brain axis

THE MATRIX OF THE MICROBIOME, THE GUT AND THE BRAIN — the gut-brain axis — is a new paradigm for understanding health. When the matrix is functioning well, the body and mind function well. When the matrix is out of balance, physical health issues such as arthritis, diabetes, gut issues such as IBS and IBD, food sensitivities, liver problems, inflammation, musculoskeletal disorders and autoimmune diseases can arise. Mental health suffers, and neurodegenerative disorders can develop.

The role of the vagus nerve

The vagus nerve (10th cranial nerve) is the longest of the cranial nerves. In Latin, the word “vagus” means wandering, an appropriate way to describe the path of this nerve. It runs from the brain stem to the transverse colon. Along the way, it innervates the larynx, esophagus, lungs, trachea, heart and most of the digestive tract. The brain and gut feedback and feed-forward loops are linked by the vagus nerve.

The long, convoluted pathway means the vagus is the main nerve of the parasympathetic nervous system, often called the “rest and digest” system. This is the autonomic system that helps the body conserve energy by slowing the heart rate (rest). The vagus nerve modulates digestion through the migrating motor complex and relaxes the ileocecal valve and other sphincter muscles in the gut (digest). The messages the vagus nerve transmits to the brain from the gut microbiome also impact the hypothalamus-pituitary axis, which in turn controls the neuroendocrine system, mood and the immune response.

Gut-brain axis call and response

The vagus nerve link is bidirectional. Approximately 80% of the messages sent along the vagus superhighway go from the gut to the brain; about 20% go in the other direction. What are they talking about?

Signals from the gut microbiome and from the gut itself tell the brain what’s going on down there; signals from the brain tell the gut what changes to make in response. The gut tells the brain about the production, expression and turnover of neurotransmitters such as serotonin and GABA, and growth factors such as BDNF (brain-derived neurotrophic factor). The gut also reports on the production of intestinal barrier chemicals and tight junction integrity, the modulation of enteric sensory afferents, bacterial metabolites, and mucosal immune regulation. The brain responds with messages that tell the gut to alter mucus and biofilm production, motility, intestinal permeability and immune function.

For example, when vagus afferent nerve fibers within the gut detect inflammatory cytokines and other indicators, such as tumor necrosis factor, created by the gut bacteria, they pass the message to the brain. The brain responds by stimulating the production of anti-inflammatory neurotransmitters that regulate the immune

Gut bacteria and brain health response

Recent research confirms the idea that gut health and brain health are tightly linked. Metabolites excreted by gut bacteria are sensed by afferent nerve endings in the gut; their level is reported to the brain via the vagus nerve. Bacterial metabolites include some substances that are very similar to brain neurotransmitters such as dopamine. In other words, microbial metabolites can interact with the brain and influence behavior and feelings.

The human gut contains more than 1,000 bacteria species. Trillions of individual bacteria are in the gut, meaning the human body contains more bacteria just in the gut than cells in the entire body. The gut microbiome weighs in at about three pounds. It contains 20 million bacteria genes; the human body has only approximately 2,000. And the gut contains far more neurotransmitter chemicals than the brain itself. In fact, about 90% of the body’s serotonin is produced in the gut by enterochromaffin (EC) cells. The process is highly dependent on the presence of gut bacteria. The bacteria grow and produce metabolites within the gut that stimulate the EC cells to produce serotonin.

Gut bacteria and autism, Alzheimer’s

Gut bacteria metabolites may also be important in a number of neurodegenerative diseases. In autism, for example, gut microbiota appear to alter the immune system and metabolism. People with autism often have higher intestinal permeability and show a higher antigenic load from gut bacteria. Their gut biome bacteria are less diverse, and Candida is twice as abundant, impacting the gut-brain axis.

People with autism also have higher than usual levels of LPS (lipopolysaccharides, also known as endotoxin) in their blood. LPS is released from the outer cell walls of gram-negative bacteria when they are destroyed. LPS leads to inflammation that carries over from the digestive tract to the bloodstream.
The presence of antibodies against LPS in the blood indicates that the endotoxin has infiltrated the systemic circulation through the intestinal wall — the well-known leaky gut syndrome. LPS elicits a strong immune response that may be closely related to autism symptoms.

Similarly, elevated LPS from intestinal permeability is noted in brain disorders such as Alzheimer’s disease, cognitive decline, dementia and mood disorders.

Damaged gut bacteria

When the gut bacteria are damaged or out of balance, the health consequences can be severe. What causes the damage? The chief culprit is the Standard American Diet (SAD), which loads the gut with highly processed foods that are high in chemical additives, sugar, and bad fats and low in fiber.

Exposure to the herbicide glyphosate (Roundup), found throughout the modern food system, is another significant cause of damage — this chemical kills beneficial gut bacteria and damages the microvilli. Glyphosate may also break down the blood-brain barrier and allow LPS and other toxins to enter the brain. Other common culprits include antibiotics and other medications, alcohol, toxic environmental chemicals such as glyphosate pesticides, and that all-purpose gut destroyer, stress. Even healthy foods can be to blame if they contain gluten or lactose or are high in lectins (an indigestible protein found in beans and nightshade plants such as peppers).

What all this comes down to is: “Gut on fire, brain on fire.” The loop is initiated by intestinal inflammation. That leads to the production of inflammatory cytokines that cross the blood-brain barrier and activate brain microglia (the brain’s immune system), causing inflammatory degeneration. At the same time, macrophages in the intestines are also activated, leading to degeneration in the enteric nervous system. The result? An ongoing cycle of inflammatory neurodegeneration throughout the brain-gut axis. The early symptoms are subtle. There’s no pain because the brain has no pain receptors and the inner lining of the gastrointestinal mucosa contains no pain fibers. The symptoms are bloating, followed immediately by brain fog.

SIBO: small intestine bacterial overgrowth

The small intestine is a harsh environment for bacteria. Some do thrive there, but the bulk of the gut bacteria are found in the colon. Small intestine bacterial overgrowth (SIBO) happens when colon bacteria travel to the small intestine and take hold, or when the bacteria naturally found in the small intestine increase too much. SIBO symptoms include bloating and flatulence, diarrhea or constipation, abdominal pain, nausea and fatigue.

SIBO can be a complication of conditions such as diabetes, IBS and concussion, but it can also occur as a result of antibiotic use, proton pump inhibitor (PPI) use, low stomach acid, decreased bile acids, and alcohol use. A low-fiber diet such as SAD slows movement in the small intestine and can lead to SIBO. Just getting older and being female are risk factors.

The excess bacteria in the small intestine can gobble up nutrients before they can be absorbed. In addition, CDTs from the harmful bacteria damage the epithelial layer, causing leaky gut from damaged tight junctions, damage to the blood-brain barrier (BBB), and systemic inflammation.

Guide patients toward change

The gut-brain axis is complex and, in today’s toxic world, easily damaged. A thorough understanding of how the brain and gut are linked gives practitioners the ability to treat the damage with relative ease by guiding patients through the needed changes to diet and lifestyle. The reward? What every practitioner wants: a patient restored to vigorous physical and mental health.

Sidebar: 7 steps to restoring the balance

RESET — The first action step is to reset the diet, lifestyle and mindset of patients. The key dietary component is an anti-inflammatory diet, one that is free of GPS: gluten, processed foods and sugar. The ketogenic diet is ideal for this, or a modified Mediterranean diet that is free of GPS and DNA (dairy, nicotine and artificial sweeteners). In addition to the basic diet, adding two teaspoons of MCT oil from coconut oil is very helpful for antimicrobial and antifungal effects. Also helpful are stress reduction techniques, such as meditation, mindfulness, yoga and regular exercise.

REMOVE — Remove foods that are damaging the gut — processed foods, sugar, dairy and gluten should be removed to allow the gut to heal and inflammation to subside. At the same time, remove unwanted pathogens to restore beneficial gut bacteria and the gut-brain axis link. Serum-derived bone immunoglobulins (SBI) help prevent immune activation by binding microbes and toxins, leading to decreased inflammation and less tissue damage. Berberine HCL activates the enzyme AMPK (AMP-activated protein kinase), sometimes called the body’s metabolic master switch. It is the first supplement to turn to for the patient with serious imbalance of the gut microbiome.

REPLACE — People with gut dysbiosis often need to replenish and replace digestive enzymes and stomach acid. Paradoxically, symptoms often attributed to excess stomach acid may actually be caused by low gastric acidity. To improve acidity, titrate betaine HCL with pepsin up to a warming dose. Pancreatic enzymes can be dosed with each meal to improve insufficiency. A comprehensive enzyme complex that includes amylase, papain, trypsin and lipase helps promote healthy digestive function.

REGENERATE — After the diet has been reset and the toxins removed, the damaged intestinal mucosa need help to regenerate and repair the intestinal wall. The amino acid glutamine is key to this process. Overall, glutamine protects muscle tissue and supports immune function during periods of immune and muscular stress. Other nutrients that may be helpful include omega-3 fatty acids (to improve bacterial diversity, downregulate TLR4, and attenuate the NF-kB pro-inflammatory signaling pathway). Other tools for regenerating the mucosa include curcumin, N-acetyl glucosamine (NAG), ginger, aloe vera and grass-fed collagen peptides, to name just a few.

RE-INOCULATE — In gut dysbiosis, the bacterial balance is disrupted. Re-inoculating the gut with high-quality prebiotics and probiotics can help restore beneficial bacteria and crowd out harmful bacteria. Fiber is crucial to resetting the microbiome — it is the fertilizer that makes a healthy microbiome flourish. Fructooligosaccharides (FOS), found in complex soluble fiber, act as prebiotics that nurture the growth of beneficial bacteria in the colon. Supplements of FOS powder containing inulin ensure regular and controlled dosing. Probiotics should be chosen for the specific beneficial bacteria in the formulation.

REINTRODUCE — When dysbiosis symptoms are reduced or gone, foods removed earlier can be gradually reintroduced. Continue to avoid GPS, DNA, fried foods and those shown by testing to cause allergic responses.

RETAIN — Retaining gains in gut integrity and overall physical and mental health is an ongoing process. Avoiding a poor diet, lack of movement and stress takes commitment and knowledge. Help your patients by educating and supporting them as they seek improved health. Going forward, gains can be retained with a daily multivitamin plus phytonutrients, vitamin D with vitamin K, omega-3 fatty acids, a quality probiotic and green drinks. Follow GPS and DNA. Regular exercise is a must.

Robert G. Silverman, DC, DACBN, DCBCN, MS, CCN, CNS, CSCS, CIISN, CKTP, CES, HKC, FAKTR, is a chiropractic doctor, clinical nutritionist, international speaker and author of Inside-Out Health: A Revolutionary Approach to Your Body, an Amazon No. 1 bestseller in 2016. The ACA Sports Council named Silverman the Sports Chiropractor of the Year in 2015. He can be contacted at


[1] Shilling M. et al. Antimicrobial effects of virgin coconut oil and its medium-chain fatty acids on Clostridium difficile. J Med Food. 2013 Dec;16(12):1079-85. doi: 10.1089/jmf.2012.0303.

[2] Gu L et al.  Berberine ameliorates intestinal epithelial tight-junction damage and down-regulates myosin light chain kinase pathways in a mouse model of endotoxinemia. J Infect Dis. 2011 Jun 1;203(11):1602-12. doi: 10.1093/infdis/jir147

[3] Joanne Slavin. Fiber and Prebiotics: Mechanisms and Health Benefits. Nutrients. 2013 Apr; 5(4): 1417–1435. Published online 2013 Apr 22. doi: 10.3390/nu5041417.

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