Why is the Vagus Nerve Important?

Gut-Brain Access

vagus nerve connecting brain and gut“Mind-body connection”? It is the link between our emotional/mental and physical selves. The link becomes evident as you learn about gut-brain access and the function of the vagus nerve.

Through two-way communication with the brain via the nervous system, endocrine system, and immune system, the gut and central nervous system form a gut-brain axis. They communicate with each other constantly, in both sickness and health.1 The gastrointestinal tract has its own nervous system that includes neurotransmitters, neurons, and electrical signals. Called the enteric nervous system, it is often referred to as the second brain. Researchers have concluded that mechanisms that degenerate the neurons in the brain also degenerate neurons in the enteric nervous system.2 For example, exercise stimulates gut motility. If the vagus nerve is impaired, as in animal models, the gut has limited motility and nutrient absorption is hindered.3

Healthy brain function. Ninety percent of your brain’s output has to do with non-voluntary functions, including the digestive and elimination system. Therefore, an impaired brain often results in a compromised digestion process.

Healthy gut function is linked to a healthy central nervous system. Changes in gut microbiota affect the nervous system. Dysfunction of the delicate interconnections between the two is closely associated with neurodegenerative conditions such as Parkinson’s and Alzheimer’s diseases.4 Thus, intestinal microbiota is directly linked to various forms of dementia due to the action of metabolic disease and chronic low-grade inflammation.5

The gut microbiota assists a number of everyday functions in the brain, including the regulation of the hypothalamic-pituitary-adrenal (HPA) axis activation state. The release of cortisol governs the activation state of brain microglia and affects cytokine release, as well as attracting monocytes from the periphery to the brain. They also can rule actions in the periphery and central nervous system by various means of communication, including vagal nerve and adrenergic nerve activation as well as effecting neurotransmitters, neuropeptides, endocrine hormones and immunomodulators.

Communication between the gut and vagus nerve affects eye movement, facial expressions, tone of voice, heart rate and heart rate variability, breathing, and the function of the spleen, liver, kidneys and intestines. It can help to reduce inflammation and to improve your immune response. It is the care-taking nerve of the body.

The vagus nerve activates the parasympathetic nervous system. When the vagus is stimulated, it elicits the relaxation response. This slows your heart rate (through the release of acetylcholine) and relays instructions to release certain proteins and enzymes to calm you down.

The Vagus Nerve is a Bridge

The mind and the body are mutually intertwined, and the vagus nerve makes the two inextricable.

As emotional beings, we often take refuge in food and drugs to help manage our feelings, particularly related to depression and anxiety. How often have you reached for cake, carbs, and candy to “feel better,” only to end up feeling groggy and sluggish afterward, regretting your decision? Conversely, we know that eating a healthy, balanced diet lifts the fog in our minds and the invisible weights on our bodies. Also, a diet high in sugar and refined carbohydrates over time can create an emotional and physical attachment to these foods, resulting in a viscous cycle around trying to manage one’s emotions through food.

The vagus nerve is a cranial nerve that acts as a bridge between the brain stem to the abdomen. “The vagus nerve delivers information from the gut to the brain.”6 It is an essential element of the parasympathetic nervous system. This system is responsible for mood control, immune response, heart rate, etc.7

The vagus nerve is like a little messenger carrying information back to the brain from the body about how the organs are functioning. It can also be called the body’s “information superhighway.”

Vagus Nerve Injury and Vision Problems

Damage to the vagus nerve causes:

      • Diminished ocular blood flow
      • Pupils dilating and contracting spasmodically (pupillary hippus)
      • Limited pupillary constriction
      • Limited depth perception
      • Increased intraocular pressure (that may lead to glaucoma)
      • Optic nerve damage
      • Difficulty getting proper image quality

Vagus Nerve Inhibition

When poor brain health affects communication to the vagus nerve, blood flow to the intestines is inhibited, in turn compromising effective functioning of the intestinal wall and normal cell regeneration. The effects can result in low hydrochloric acid production, poor enzyme release, poor gut stretching and contraction ability, and yeast and bacteria overgrowth.8

      • Irritable bowel syndrome may be due to a disturbed neural function along the gut-brain axis.
      • Increased permeability to allergens, toxins, and pathogens, leading to immunological stress response and inflammation.9
      • GI system inflammation causes rashes, pain, food sensitivities, brain health issues and other imbalances. When the brain is affected, this can compromise the GI system, which can then cause more inflammation, creating a viscous cycle.10 Irritable bowel syndrome and inflammatory bowel disease are linked to gut-brain axis dysfunction.11
      • Chronic inflammation and the brain. Many studies have shown a connection between inflammation and Alzheimer’s, dementia, and cognitive decline, including circulating inflammatory markers.12 13 Inflammation in AD pathology is linked to activated inflammatory cells (microglia and astrocytes) and inflammatory proteins (e.g. cytokines), which surround amyloid plaque and neurofibrillary tangles.
      • Association with Alzheimer’s. Some unique microbial patterns are seen in patients with mild cognitive impairment. One participant of the gut microbiome family, proteobacteria, positively correlated in patients with AB-42. Patients with AB-40 have a negative correlation with fecal propionate and butyrate. Several bacteria are affected in different ways in normal or impaired patients depending on their diet.14
      • Depression and anxiety. Microbiota dysfunction is linked to depression and anxiety.15
      • Cardiovascular disease. There is an increasing amount of proof suggesting that gut microbiota, through a variety of processes, can influence physiological processes important for the development of cardiovascular disease.16 The resulting restrictions in the circulatory system contribute to neurodegenerative conditions.

Blood-brain Barrier

The blood-brain barrier consists of several parallel barriers, the most studied being the vascular barrier and the choroid plexus. It is a thin lining that prevents pathogens and other unwanted particle from reaching the brain. Because leaky gut releases such pathogens across the mucosal barrier, they have a chance of also reaching the brain. Such release includes cytokines and neurotransmitters arising from inflammation in the gut.17 18

The inflammation factor is important because researchers are looking at a molecule called microRNA-155, which is elevated with inflammation. This molecule can create microscopic gaps in the blood-brain barrier that let material through, overstimulating the brains inflammatory response and triggering brain inflammation.19 20

Stimulating the Vagus Nerve

To recap, the vagus nerve:

      • Controls inflammation.
      • Allows normal digestion and bowel movements
      • Triggers normal stomach acid production
      • Communicates with the gallbladder to release bile
      • Communicates with the pancreas to release digestive enzymes
      • Slows heart rate and breathing when relaxation is appropriate
      • Solidifies memories

Studies have shown that the vagus nerve is key in solidifying memories.21  Stimulating it strengthens both memory formation and storage and therefore shows promise as an option for Alzheimer’s treatments and the blocking of traumatic memories.22

Here are some methods to stimulate your vagus nerve at home:

      • Meditation
      • Exercise
      • Cold-water immersion
      • Singing/humming
      • Add cultured products in your diet such as including kefir, yogurt, Greek yogurt, and traditional buttermilk may be helpful.
      • Fermented foods in diets may confer gastrointestinal and cognitive benefits. These include kimchi, sauerkraut, kefir, fermented soy, miso and kombucha (be careful because alcohol is not good for everyone, especially people with eye disease) provide your gut with trillions of beneficial bacteria.
      • Intermittent fasting is not a full fast, but limiting your daily caloric intake to 500 or 600 calories a day. This restriction for a few days will allow your body to repair the gut’s lining. The healing foods listed above are perfect choices to eat during intermittent fasting. Intermittent fasting works best when it is synchronized with the earth’s natural circadian rhythm. Therefore, fast in the evening, after sunset.
      • Probiotics have been shown to have positive effects for the GI system and reducing leaky gut. Probiotics are the beneficial microorganisms that inhabit the gastrointestinal tract. They can be used to reduce intestinal permeability23 by strengthening the epithelial tight junctions and preserving mucosal barrier function (especially L. plantarum24).

Probiotics not only help maintain normal function of the gut mucosa, but also may protect mucosa from injurious factors such as toxins, allergens, and pathogens, and support a healthy immune system.25

Supporting Good Health

All of the above recommendations support the health of the vagus nerve and the brain-gut axis and support overall good health as well.  The foundations of good health are exercise, enough sleep, healthy food, rest, relaxation, and re-creation. So be sure to slow down the fast pace of life and take time to take care of yourself.

Related Supplements

NeuroRenew™ 120 vegcaps (D05099)

Super Lion’s Mane 120 vegtabs

Intestinal Repair Complex 160 gms

ION Gut Support 32 fl oz

Probiotics: FloraMend Prime Probiotic® 30 caps

General Eye Supplements

Advanced Eye & Vision Support Formula (whole food) 60 vcaps

Dr. Grossman’s Advanced Eye and Dr. G’s Whole Food Superfood Multi120 Vcap Combo – 2 months supply

Dr. Grossman’s Bilberry/Ginkgo Combination 2oz (60ml)

Dr. Grossman’s Meso Plus Retinal Support and Computer Eye Strain Formula with Astaxanthin 90 vcaps

Natural Brain Support Book and Nutrient Package


  1. Grenham S, Clarke G, Cryan JF, Dinan TG. (2011). Brain-gut-microbe communication in health and disease. Front Physiol. 2011; 2():94.
  2. Wade PR, Cowen T. Neurodegeneration: a key factor in the ageing gut. Neurogastroenterol Motil. 2004 Apr;16 Suppl 1:19-23.
  3. Wang Y, Kondo T, Suzukamo Y, Oouchidaa Y, Izumi S. (2010). Vagal nerve regulation is essential for the increase in gastric motility in response to mild exercise. Tohoku J Exp Med. 222(2):155-62.
  4. Zhu X, Han Y, Du J, Liu R, Jin K, et al. (2017). Microbiota-gut-brain axis and the central nervous system. Oncotarget. Aug 8;8(32):53829-53838.
  5. Alkasir R, Li J, Li X, Jin M, Zhu B. (2017). Human gut microbiota: the links with dementia development. Protein Cell. Feb;8(2):90-102.
  6. Seymour T. (2017). Everything You Need to Know About the Vagus Nerve. Med News Today. Retrieved Apr 14 2023 from https://www.medicalnewstoday.com/articles/318128#Vagus-nerve-stimulation.
  7. Breit S, Kupferberg A, Rogler G, Hasler G. (2018). Vagus nerve as modulator of the brain-gut axis in psychiatric and inflammatory disorders. Front Psychiatry. 2018; 9: 44.
  8. Bansal V, Constantini T, Ryu SY, Peterson C, Loomis W, et al. (2010). Stimulating the central nervous system to prevent intestinal dysfunction after traumatic brain injury. J Trauma. May;68(5):1059-64.
  9. Duggan C, Gannon J, Walker WA. (2002). Protective nutrients and functional foods for the gastrointestinal tract. Am J Clin Nutr. May; 75(5):789-808.
  10. Bansal V, Constantini T, Kroll L, Peterson C, Loomis W, et al. (2009). Traumatic brain injury and intestinal dysfunction: uncovering the neuro-enteric axis. J Neurotrauma. Aug:26(8):1353-9.
  11. Bonaz BL, Bernstein CN. (2013). Brain-gut interactions in inflammatory bowel disease. Gastroenterology. Jan; 144(1):36-49.
  12. Harris TB, Benjamin EJ, Au R, Kiel DP, Wolf PA, et al. (2007). Inflammatory markers and the risk of Alzheimer’s disease: the Framingham Study. Neurolgy. May 29; 68(22):1902-8.
  13. Zuliani G, Ranzini M, Guerra G, Rossi L, Munari MR, et al. (2007). Plasma cytokines profile in older subjects with late onset Alzheimer’s disease or vascular dementia. J Psychiatr Res. Oct; 41(8):686-93.
  14. Nagpal R, Neth BJ, Wang S, Craft S, Yadav H. (2019). Modified Mediterrean-ketogenic diet modulates gut microbiome and short-chain fatty acids in association with Alzheimer’s disease markers in subjects with mild cognitive impairment. EBioMedicine. Sep;47:529-542.
  15. Dinan TG, Cryan JF. (2013). Melancholic microbes: a link between gut microbiota and depression? Neurogastroenterol Motil. Sep; 25(9):713-9.
  16. Hazen SL, Smith JD. (2012). An antiatherosclerotic signaling cascade involving intestinal microbiota, microRNA-10b, and ABCA1/ABCG1-mediated reverse cholesterol transport. Circ Res. Sep 28; 111(8):948-50.
  17. Biesmans S, Bouwknecht JA, Ver Donck L, Langlois X, Acton PD, et al. (2015). Peripheral Administration of Tumor Necrosis Factor-Alpha Induces Neuroinflammation and Sickness but Not Depressive-Like Behavior in Mice. Biomed Res Int. 2015():716920.
  18.  Gądek-Michalska A, Tadeusz J, Rachwalska P, Bugajski J. (2013). Cytokines, prostaglandins and nitric oxide in the regulation of stress-response systems. Pharmacol Rep. 65(6):1655-62.
  19. Lopez-Ramirez MA, Wu D, Pryce G, Simpson JE, Reijerkerk A, et al. (2014). MicroRNA-155 negatively affects blood-brain barrier function during neuroinflammation.  FASEB J. Jun;28(6):2551-65.
  20.  Block ML, Hong JS. (2005). Microglia and inflammation-mediated neurodegeneration: multiple triggers with a common mechanism. Prog Neurobiol. Jun;76(2):77-98.
  21. Clark KB, Naritoku DK, Smith DC, Browning RA, Jensen RA. (1999). Enhanced recognition memory following vagus nerve stimulation in human subjects. Nat Neurosci. 1999:2;94-98.
  22. Adelson R. (2004). Stimulating the vagus nerve: memories are made of this. Retrieved Apr 17 2023 from www.apa.org/monitor/apr04/vagus.
  23. Lamprecht M, Bogner S, Schippinger G, Steinbauer K, et al. (2012). Probiotic supplementation affects markers of intestinal barrier, oxidation, and inflammation in trained men; a randomized, double-blinded, placebo-controlled trial. J Int Soc Sports Nutr. 9(1):45.
  24. Markowiak P, Slizewska K. (2017). Effects of Probiotics, Prebiotics, and Synbiotics on Human Health. Nutrients. Sep;9(9):1021.
  25. Rao RK, Samak G. (2013). Protection and Restitution of Gut Barrier by Probiotics: Nutritional and Clinical Implications. Curr Nutr Food Sci. May 1; 9(2): 99–107.