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Vagus Nerve – What is it and how does it work?

Vagus Nerve – also known as the wandering nerve, directly connects the brain and gut to form the brain and gut axis and enteric nervous system. Over history, many investigations on this nerve also found that it connects intricately with many vital organs in the body in order to assist in communication pathways. It wanders its little feelers around every organ except the adrenal glands and thyroid.

History of the vagus Nerve

Throughout history and discovery of the nerve, much research has been done into its sole purpose, many arguments have stemmed about the role it plays primarily, but one conclusion can be made and this is that it, in fact, plays multiple crucial roles within the body:

– Communication with the amygdala controlling the secretion of nor-epinephrine for the purpose of memory creation and recall.
⁃ Acetylcholine production to stimulate the lungs for the purpose of breathing.
⁃ Controls the inflammatory response and calming cascade to keep the body in a state of homeostasis when faced with any inflammatory mediators such as adipokines and cytokines and does this via the communication to anti-inflammatory neurotransmitters.

Just to name a few!

Vagus Nerve Severing!

Interestingly, with all of the roles that this vital nerve contributes to in the body, during the first discovery period, the scientific theory suggested that if it played a role in the purpose of digestion and excretion of stomach acids, stimulation of the pancreas and large intestine; then it would be the sole contributor to digestion dis-ease such as irritable bowel, Peptic ulcers, H.Pylori, reflux and more.

The method for fixing these digestive issues…sever the vagus nerve! While this proved their theory correct, and it did help with the mentioned digestion issues, it, in turn, made matters far worse for the newly operated on a patient, so much so that it would make you want to dial back the clock….

What would happen if we disabled the Vagus Nerve?

Vagotomy has been around for a very long time and this coincides with the severing of the Vagus nerve, though the research has come out now suggesting to only implement this as a last resort due to the importance of other contributing factors in the body, some of which areas affected are:

  • Heart rate irregularities.
  • Induced excessive sweating and perspiration.
  • Deregulation of satiety in the body due to no gut-brain axis communication.
  • The severing of the nerve would no longer mean the body could regulate inflammation response and as such heightens inflammation throughout the body.
  • Impact and disable the process of Neurogenesis which is the constant birth and formation of Neurons in areas of the brain formed from Neural stem cells.
  • Erratic activity and poor insulin and glucose control within the body leading to insulin disorders.

More research is still being compiled into the negative effects of severing or disabling the Vagus Nerve, so far though it looks as if the Cons outweigh the pros in effect.

Signs of a Dysfunctional Vagus Nerve

  1. Insulin disorders, obesity, and unexplainable weight gain. Because the Vagus Nerve directly impacts insulin secretion and glucose balance within the body, a common symptom of an unstimulated and dysfunctional Vagus Nerve is poor insulin homeostasis. There is also some vast study was done that may indicate the Vagus Nerve directly impacts the function of the thyroid too. [3]
  2. Anxiety, Depression, and mood irregularities. Because the Vagus Nerve works so closely with the gut microbiome, both factors need to be taken into account when looking into Gut as a possible causative factor in Anxiety, Depression, and unexplained Poor Mood. Often in Treatment-resistant forms of depression and anxiety, patients go without relief for their unexplained symptoms that cannot be healed with Pharmaceutical ailments. [7]

The Feedback that is provided back to the brain from the gut Microbiome colonization has a lot to do with the chemicals being released and may make it easier to understand how to colonize the gut to help our mental health. For instance, in many studies linking the gut-brain axis, Bifidobacterium and lactobacillus are used alongside famously known anti-depressants and shown to be equally if not more effective in treatments for depression and anxiety –  test subjects showed far more motivation, were able to adapt to stress far better and their anxiety and overdrive of fight-or-flight response became level. [5]

This takes the commonly used terminologies of “Gut Feeling” “Gut instinct” and ‘Nervous” to a whole new level…

Ever been stressing about an event, meeting, confrontation, driving test, or interview and felt like you either needed to vomit or run to the loo because all of a sudden, your bowels have informed you that you need to go pronto even if you went an hour ago?

This is often what we call nerves or jitters, and we have all had that churning feeling in our gut that we can describe as feeling ill right before a hugely important matter was about to take place. Or perhaps had that odd, ‘gut feeling’ that something was about to happen or wasn’t quite right?

For many of the population suffering from IBS, also now known to be a Gut-Brain axis disorder, even everyday stress sets this feeling off and you need to evacuate the bowels in a hurry! [21]

What is this internal Conversation that our Guts and Brains have autonomously where they decide that we need to feel this way? This conversation happens via the Vagus Nerve Highway and the central, sympathetic, parasympathetic, and autonomic nervous systems all interconnect to communicate, this all happens just as quickly as cars on a highway, The Neurotransmitters firing, the chemicals rushing…everything!  The stress response is picked up by the Vagus nerve and it sets all of these crazy things into action as a survival mechanism. This is most likely why the Enteric nervous system is known as the second brain, all of this constant feedback to the brain shuttling back and forth constantly and altering everything to adapt; it’s amazing how quickly things are set into motion in order to survive whatever this stress is.

How do you Balance and Stimulate the Vagus Nerve?

There are many compounds that are easily accessible in everyday diets that can balance and correct a dysfunctional Vagus Nerve, that interestingly also impact the gut microbiome status… Year of the gut like we have been saying, it’s a whole world down there waiting to be discovered!

Foods:

As mentioned in many previous podcast and content, Polyphenols play a huge role in not only balancing the colonies of our gut but they also directly stimulate the vagus nerve to enhance digestion, pancreatic function, correct insulin response and are now being hugely studied as a cure for obesity, Nature really does know best, that’s why she put the polyphenols in the skins of fruits and vegetables, grains and seeds occurring organically as they should.

Over the years, our taste receptors and our sugar-loving bugs have made us prefer and seek out only the delicious sugary content of the Fruits, sugarcane, juices, and sweeter sections of plants to please our tongue and bugs. Not knowing that the seeds and peel of these delicious fruits of nature may also help to control; these sugar-loving bugs so they don’t overpopulate, leading to gut dysbiosis, diabetes, Candida overgrowth and much more!

Polyphenols can be found in all sorts of foods, herbs, and spices…. Here are a few you may have in your pantry at home that you can throw together in order to kickstart some great gut and mental health!

Herbs: Cloves, Star anise, Cinnamon, cumin, ginger, rosemary, thyme, basil, peppermint, and oregano.

Teas: Black tea and Green tea.

Berries: Blackberries, Blueberries, cherries, strawberries, Raspberries, Black Grapes with the thicker skin and seeds.

Seeds: Cumin Seeds, Flax, Celery, apple seeds.

Nuts: Many skins contained on the nut are beneficial especially present in Walnuts and hazelnuts.

Fruits: Most, but more potently found in Apricot, blood orange, and pomegranates.

Bitter Taste receptors on the tongue stimulate the Vagus Nerve: Much study has been done into taste receptors on the tongue and how they impact metabolic and digestive processes in the gut for the purpose of acid secretion, insulin secretion from beta cells of the pancreas increasing total Glucose uptake from the gut and peptide Ghrelin which has loads of appetite-inducing properties, this can be found when inducing Carbohydrates and Glutamate rich foods, of which Glutamates are well-known Neurotransmitter irritants.

To combat this; research is now being done into the purpose of Bitter Taste receptors known as the T2R Receptors. What is coming of this is that they actually contribute to the release of cholecystokinin (CCK) which actually reduces gut motility and slows down digestion, increasing the satiety effects. Intakes of Toxins from food that activate the T2R Pathway of receptors for example Polyphenols contribute to satiety most likely as a survival mechanism to decrease any further intake of these natural toxins. [22]

Take home message

The Gut-Brain Axis is one of the most amazing and understudied systems of the body, and with modern technology we may find that this allows us to finally approach the individual as the individual instead of an umbrella approach, being that the gut is so diverse and unique to the person.  This is extremely exciting for the future of modern medicine.

 

References:

  1. O’keane V, Dinan TG, Scott L, Corcoran C. Changes in hypothalamic-pituitary-adrenal axis measures after vagus nerve stimulation therapy in chronic depression. Biol Psychiatry. 2005;58(12):963-8. 
  2. Carnethon MR, Jacobs DR, Jr, Sidney S, Liu K. Influence of autonomic nervous system dysfunction on the development of type 2 diabetes: the CARDIA study. Diabetes Care. 2003;26:3035–3041. 
  3. Vagus nerve stimulation: quality control in thyroid and parathyroid surgery. J Laryngol Otol. 2000 Feb;114(2):125-7.Lambert AW1Cosgrove CBarwell JOxenham SWilkins DC.
  4. Chapter 6 Neurogenesis in the Adult and Aging Brain. David R. Riddle and Robin J. Lichtenwalner.
  5. The Gut-Brain Axis: The Missing Link in Depression Alper Evrensel and Mehmet Emin Ceylan
  6. Kynurenine Pathway of Tryptophan Metabolism: Regulatory and Functional Aspects Abdulla A-B BadawyInt J Tryptophan Res. 2017
  7. “Gut Vagal Afferents Differentially Modulate Innate Anxiety and Learned Fear” and was published May 21, 2014 in the Journal of Neuroscience.
  8. Perez-Jimenez J, Neveu V, Vos Fm Scalbert A. Identification of the 100 richest dietary sources of polyphenols: an application of the Phenol-Explorer database. Eur J Clin Nutr 2010; 64(S3):S112-S120.
  9. Punicic acid: A striking health substance to combat metabolic syndromes in humans Muhmmad Asim ShabbirMoazzam Rafiq KhanMuhammad SaeedImran PashaAnees Ahmed Khalil, and Naila Siraj
  10. Taste isn’t just for taste buds anymore Thomas E. Fingercorresponding author1 and Sue C. Kinnamon2
  11. Phenolic Compounds as natural and Multi-functional anti-obesity agents: a ReviewCelia Rodriguez-Perez, Antonia Segura -Carretero & Maria Del Mar Contreras
  12. Bitters: Time for a new Paradigm Michael K. Mcmullen. 2015 May
  13. Bitter Taste receptor Agonists alter Mitochondrial Function and Induce Autophagy in airway smooth muscle cells. Shi Pan, Pawan Sharma. Cnter for translational medicine. April 27, 2017
  14. Bitter Tate of Brassica Vegetables: The role of genetic factors, receptors, isothiocyanates, Glucosinolates and flavour context. Martyna N. Wieczorek, Michal Walczak. 2017
  15. Curcumin attenuates collagen-induced inflammatory response through the “gut brain axis” Journal of Neuroinflammation. Dou y. Jan 6, 2018
  16. Vagal Activities are involved in antigen Specific immune inflammation in the intestine. Hong Liang, dept. of Neurosurgery. 21/02/2011
  17. Genetic, Functional, and Phenotypic Diversity in Tas2R38 mediated Bitter Taste Perception. Maik bahrens, Howard C. Gunn 1 July 2013
  18. Role of Microbiota in Pathogenesis of functional Disorders of the lower Gi Tract: Work in progress. 6 July 2017. Joanna Jalanka
  19. Taste Receptors in the gastrointestinal Tract. Functional Implications of bitter taste receptors in Gastrointestinal Chemosensing. Sternini C. 31 oct 2006
  20. Stress & Gut Brain axis: Regulation by the Microbiome. Jane A. Foster Linda Rinaman, John F. Cryan 15.12.2016
  21. Irritable bowel syndrome: A microbiome-gut-brain axis disorder? World J Gastroenterol. 2014 Oct 21; 20(39): 14105–14125. Published online 2014 Oct 21. doi: 10.3748/wjg.v20.i39.14105 Paul J KennedyJohn F CryanTimothy G Dinan, and Gerard Clarke

  22. Bitter taste receptors and α-gustducin regulate the secretion of ghrelin with functional effects on food intake and gastric emptying. Proc Natl Acad Sci U S A. 2011 Feb 1;108(5):2094-9. doi: 10.1073/pnas.1011508108. Epub 2011 Jan 18. Janssen S1Laermans JVerhulst PJThijs TTack JDepoortere I.