Can Targeting the Vagus Nerve Improve Digestive Symptoms? – A Case Study Approach

April 15th, 2024

Digestive symptoms are common among Americans, likely related to a typical inflammatory diet and other lifestyle-related factors. Standard of care treatment may overlook important root causes, which makes complete healing difficult.

Emerging research suggests that targeting the vagus nerve could be an important component of a functional nutrition care plan that addresses root cause solutions to improve a variety of gastrointestinal symptoms. In this article, we’ll discuss what you need to know about the vagus nerve and how it impacts digestive function. We’ll also share some simple strategies for improving vagal tone and highlight a client case study.

What is the Vagus Nerve?

The vagus nerve (VN) (10th cranial nerve) is the longest nerve in the body extending from the brainstem to various areas (1):

  • Pharynx
  • Larynx
  • Esophagus
  • Stomach
  • Intestines
  • Lungs
  • Heart
  • Liver
  • Spleen
  • Kidneys
  • Pancreas

It’s a paired nerve meaning it has right and left branches, with afferent (sensory) and efferent (motor) functions. The afferent fibers (80%) carry information from the digestive tract (and other organs) to the central nervous system (CNS) and the efferent fibers (20%) help to control digestive tract (and other organ) functions. (1)

To understand why the VN is becoming a target of therapy in GI disorders, we need to briefly review the stress response.

The Vagus Nerve and the Stress Response

The autonomic nervous system (ANS) helps maintain homeostasis in the body. One branch of the ANS, the sympathetic nervous system (SNS), is responsible for the fight-or-flight response. It increases your heart rate, respiratory rate, and blood flow to the extremities during times of stress. The other branch, the parasympathetic nervous system (PNS), is responsible for the rest and digest state. The PNS is largely controlled by the VN. It decreases your heart rate and respiratory rate, and promotes a sense of calm allowing your body to recover and digest nutrients appropriately. (2)

When the SNS is constantly stimulated (chronic stress), PNS function (and your ability to rest and digest) declines leading to inflammation and a variety of health consequences including digestive dysfunction.

Measuring Vagal Tone

Vagal tone refers to how well the VN communicates with the gut and other organs. Heart rate variability (HRV) is thought to be one indirect measure of vagal tone. A higher HRV indicates better overall health and as reported in Behavioural Pharmacology “can be considered an index of psychological and physiological resilience”. (3)

The Gut-Brain Connection

A properly functioning VN ensures bidirectional communication along the gut-brain axis and assists with (1):

  • Motility
  • Sensitivity
  • Secretion
  • Permeability
  • Immunity

VN efferent fibers join with neurons in the digestive wall to ensure proper motor and secretory function.(1)  VN afferent fibers tell the CNS what’s going on in the gut, like when nutrients are present after a meal. (1) Normally this is an unconscious process, but when inflammation (or other pathological condition) is present, the VN afferent fibers can signal the spinal cord, increasing our consciousness of visceral pain.  This alteration in interoception (sense of the internal state of the body) is thought to be a contributing factor in many disorders including inflammatory bowel disease (IBD) and functional digestive disorders. (1), (6)

Gastrointestinal Functions of the Vagus Nerve

Here are some of the ways VN function affects digestion:

  • Liver and gall bladder function (4): When the body is relaxed, the VN increases blood flow to the liver, controls the cells that are responsible for producing bile and bile salts, and the transportation of bile into the gallbladder and small intestine for proper fat absorption by the enterocytes.
  • Pancreatic enzyme release (5): When a meal is consumed, the VN sends signals to the pancreas to release digestive enzymes to break down the components of your meal into absorbable units.
  • Gut motor activity (6): The VN signals the smooth muscle of the digestive tract to propel food through the digestive process (peristalsis).
  • Gut inflammation (4): The VN signals the gut via the neurotransmitter acetylcholine to calm immune activation and decrease gut inflammation.
  • Relays information from the gut microbiome (7): The bacteria in the gut use the VN to relay information to the brain.


Activating the Vagus Nerve to Improve Vagal Tone

Supporting vagal tone may be one option for improving VN function and GI symptoms. VN stimulation using an implanted device is one available therapy. But here’s a list of natural ways to activate the VN (3, 8, 9, 10, 11, 12, 13):

  • Anti-inflammatory diet with adequate choline (beef and beef liver, eggs, soybeans, chicken, fish)
  • Breathing exercises
  • Optimizing sleep
  • Cold exposure
  • Humming or chanting
  • Gargling
  • Yoga
  • Meditation
  • Laughing
  • Music therapy
  • Exercise
  • Sunlight
  • Supplements (probiotics and omega-3 fatty acids)

Let’s take a look at how you might incorporate some of these into an IFNA-based functional nutrition care plan.

Case Study

Mallory, a 27-year-old female, complained of significant digestive distress and anxiety. She felt nauseous after meals and had severe stomach pain after eating at times. She struggled with gas and bloating, especially after eating cruciferous vegetables and she had been told in the past that her stomach lining was inflamed. Mallory had a lifelong history of disordered eating, but said she had worked to resolve this with a therapist. She had also used antibiotics frequently for sinusitis.

Mallory was taking a multivitamin, vitamin D3, and omega-3 fatty acid supplements and was on prescription medication for depression and anxiety. She had a difficult time falling asleep and her sleep was disrupted, so she would end up lying in bed for long periods of time. Her initial symptom score of 106 indicated severe symptoms. Mallory said she wanted to feel better and learn what foods she could eat that wouldn’t cause GI distress.

While there’s no direct evidence, we can assume Mallory’s vagal tone is compromised, which could be negatively affecting her digestive function. By implementing stress management techniques like meditation and mindful movement, removing inflammatory foods, and adding in personalized supplementation, VN and digestive function should improve.

Mallory’s initial plan:

  1. Full elimination diet for four weeks to remove allergenic and inflammatory foods (alcohol, beef, chocolate, coffee, soft drinks, tea, corn, dairy products, eggs, gluten, peanuts, pork, processed meats, shellfish, soy, and sugar), which are known to decrease HRV. (3)
  2. At-home stomach acid test (indicated adequate stomach acid).
  3. Meditation for five minutes upon waking and 5 minutes at mid-day.
  4. Sleep hygiene tips to include:
  • Being in bed by 10:30 pm and up eight hours later to avoid prolonged sleep.
  • Avoid blue light for 1 hour before bedtime.
  1. Nutritional supplements:
  • Cortisol Manager to target stress and sleep
  • Lactobacillus/Bifidobacterium probiotic to target the gut microbiome
  • Magnesium glycinate 200 milligrams before bed to promote relaxation and restful sleep
  • Continue taking vitamin D3, MVI, and omega-3 (2,000 milligrams per day)

After four weeks, Mallory’s symptom score had dropped to 62 and she experienced resolution of most of her GI symptoms. She had not yet incorporated meditation but she was following the elimination diet. Of note, she did consume gluten at a birthday party and experienced a recurrence of bloating. She was struggling to be creative at meal time, which was increasing boredom with meals.  Mallory was participating in a formal exercise program twice weekly but felt she was sedentary overall.  Her bedtime habits had improved and she was in bed by 11 pm most nights.

Additional goals:

  1. Continue the elimination diet for four more weeks. Meal suggestions were provided to prevent boredom.
  2. Add a 10-minute walk after every meal.
  3. Implement meditation for 3 minutes once per day.

After four weeks, Mallory’s symptom score was down to 43. Her GI symptoms had not returned but she was having a particularly stressful time and had resumed professional therapy. She was still following the elimination diet but felt extra stress when trying to plan meals. She had implemented a daily meditation and felt it was helpful.

Additional goals:

  1. Begin reintroducing the healthy eliminated foods in a step-by-step manner. Mallory was educated to keep a food and symptom journal (via the Healthie app) during the reintroduction. She was encouraged to continue to avoid regular coffee and to consume six cups of leafy greens daily.
  2. Add in daily sun exposure and spend as much time in nature as possible.

At the final follow up, Mallory’s symptom score was down to 18 and she reported feeling great. She had successfully added most of the healthy eliminated foods back without any recurrence of GI symptoms.  She was meditating daily and noted her anxiety had significantly improved.  Mallory said she planned to continue with her healthy changes and was looking forward to continuing her health journey.

Personalization is Key

Targeting the VN to improve GI function is an emerging area of research. While many of the studies have focused on electrical VN stimulation, natural therapies like diet, meditation, humming, gargling, and yoga are also promising.

Since improving vagal tone requires flipping the switch from fight-or-flight to rest and digest, a single strategy like adding omega-3 fatty acids or encouraging laughter for example isn’t likely to move the needle much in terms of symptom relief. For the greatest impact, functional nutritionists should consider the entire clinical picture and tailor the nutrition and lifestyle plan to address the underlying imbalances that may be affecting VN function.

To learn more about functional nutrition, REGISTER HERE for your IFN Academy training today!

By: Kellie Blake, RDN, LD, IFNCP



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