30 Ways to Stimulate Your Vagus Nerve + Functions & Disorders
Posted: Fri Jun 21, 2019 9:01 pm
I’m posting this article on the vagus nerve for several reasons. I’ve started a dialogue with my body and actually asked it to help me figure what some of my health issues are about. I’ve long thought that communicating directly with your body will actually stimulate a response, as in, your body really does know best. I was sitting down at the barn milking one morning and kept having the word vagus pop in my mind. Vagus? Vagus nerve? Seemed vaguely familiar but wondered why such a strange word would suddenly pop in my mind. I promised to look it up when I went in, then promptly forgot about it. Then Christine posted something, I believe on FB that was saying something about the vagus nerve, and suddenly I remembered I was going to look it up. I found the following article, which I will post most of (it’s very long, so if you want to read the whole thing go to the link).
Also, I’m not sure about all 30 ways to stimulate your vagus nerve, although some of them seem quite reasonable and easy to try. I do think your body’s own wisdom can guide you in the right direction, and certainly am having some of the symptoms. There are so many systems operating inside our physical body, that when one thing gets out of whack, it can affect many other areas of function. And, I’m long past not trusting our current mainstream medical system to figure anything out (I hope I don’t get in trouble for saying that).
30 Ways to Stimulate Your Vagus Nerve + Functions & Disorders
By Joe Cohen, BS Last updated: May 31, 2019
https://selfhacked.com/blog/32-ways-to- ... -about-it/" onclick="window.open(this.href);return false;
The vagus nerve is critical to optimal health, no matter what your issues are. In this post, we will tell you how to stimulate it, and how it affects your health.
What is the Vagus Nerve and Its Function?
In people with fatigue, food sensitivities, anxiety, gut problems, brain fog, and depersonalization, the vagus nerve is almost always at play. These people have lower vagal tone, which means it has a lower ability to perform its functions.
The only question is which aspect of the vagus nerve is malfunctioning and to what extent it is the problem vs. other aspects of your biology.
The vagus nerve is part of the parasympathetic nervous system, referred to as the rest-and-digest system. It’s not the only nerve in the parasympathetic system, but it’s by far the most important one because it has the most far-reaching effects.
The word vagus means “wanderer,” because it wanders all over the body to various important organs.
The vagus nerve affects the brain, gut (intestines, stomach), heart, liver, pancreas, gallbladder, kidney, ureter, spleen, lungs, reproductive organs (female), neck (pharynx, larynx, and esophagus), ears, and tongue.
Given the importance of the vagus nerve to the gut (and other organs), when it’s not working properly, it will cause digestive disorders including dyspepsia, gastroparesis, GERD, ulcerative colitis, anorexia, and bulimia, to name a few.
How It Affects Your Body
Brain
In the brain, the vagus nerve helps mood and controls anxiety and depression.
The vagus nerve is largely responsible for the mind-body connection since it goes to all the major organs (except the adrenal and thyroid glands).
It’s intimately tied to how we connect with one another — it links directly to nerves that tune our ears to human speech, coordinate eye contact, and regulate emotional expressions. It influences the release of oxytocin, a hormone that is important in social bonding [1].
Studies have found that higher vagal tone is associated with greater closeness to others and more altruistic behavior [2].
Vagus activity of a child can be affected by their mother. Infants had lower vagus activity with mothers who were depressed, angry, or anxious during pregnancy [3].
Some studies suggested that the vagus nerve is important for getting in the mental state of “flow”. It’s believed that the combination of sympathetic (fight-or-flight) and vagus activation creates the right environment for a flow state [1].
Vagus nerve stimulation might increase wakefulness (by increasing orexin in the prefrontal cortex). It has been shown to decrease the amounts of daytime sleep and rapid eye movement in epilepsy patients with traumatic brain injury and also promoted the recovery of consciousness in comatose rats after traumatic brain injury [4].
However, the vagus nerve also might cause ‘sickness behavior’ (fatigue, sleepiness, depression, anxiety, appetite loss, pain, lowered motivation, and failure to concentrate) in an inflammatory state (IL-1b) [5].
Gut
In the gut, it increases stomach acidity, digestive juice secretion, and gut flow. Since the vagus nerve is important for increasing gut flow (motility), having less vagus activation will increase your IBS risk, which is a result of slower flow [6].
Stimulating the vagus nerve increases the release of histamine by stomach cells, which helps release stomach acid [7]. So, low stomach acidity is usually, in part, a vagus nerve problem. By releasing intrinsic factor, the vagus nerve is important to help you absorb vitamin B12.
Satiety and relaxation following a meal are in part caused by activation of the vagus nerve’s transmission to the brain in response to food intake [8].
The vagus nerve is important in conditions like GERD, not only because it controls stomach acidity, but also because it controls the esophagus.
Heart
In the heart, it controls heart rate and blood pressure. Vagus activation will lower the risk of heart disease, among other lethal diseases [9].
Liver, Pancreas, and Gallbladder
In the liver and pancreas, it helps control blood glucose balance.
In the gallbladder, it helps release bile, which can help you get rid of toxins and break down fat.
Kidney and Bladder
The vagus nerve promotes general kidney function. It helps with glucose control and increases blood flow, which improves blood filtration. Vagus activation also releases dopamine in the kidneys, which helps excrete sodium and, thereby, lower blood pressure [10, 11].
The vagus nerve also goes to the bladder. A side effect of its stimulation is urinary retention, which means that less vagus stimulation can cause you to urinate frequently. Indeed, many of my clients complain about frequent urination (also due to low vasopressin, low aldosterone, and high cortisol) [12, 13].
Spleen
In the spleen, it can reduce inflammation. Note that vagus activation will reduce inflammation in all target organs (by releasing acetylcholine), but when it activates in the spleen the response will probably be more systemic [14].
It helps control fertility and orgasms in women by connecting to the cervix, uterus, and vagina. Women can actually experience orgasms simply from the vagus nerve.
Mouth and Ears
In the tongue, it helps control taste and saliva; while in the eyes, it helps release tears.
The vagus nerve explains why a person may cough when tickled on the ear, such as when trying to remove ear wax with a cotton swab.
Vagus nerve stimulation helps people with tinnitus because of its connection to the ear.
30 Ways to Stimulate the Vagus Nerve
1. Cold
Studies show that when your body adjusts to cold, your fight-or-flight (sympathetic) system declines and your rest-and-digest (parasympathetic) system increases, which is mediated by the vagus nerve [15].
Any kind of acute cold exposure will increase vagus nerve activation [16].
You can dip your face in cold water to start. I’ve graduated and now take fully cold showers, expose myself to cold, and drink cold water.
2. Singing or Chanting
Singing increases Heart Rate Variability (HRV) [1].
Humming, mantra chanting, hymn singing, and upbeat energetic singing all increase HRV in slightly different ways [1].
I do Om chanting in my infrared sauna.
Singing initiates the work of a vagal pump, sending relaxing waves through the choir [1].
Singing at the top of your lungs works the muscles in the back of the throat to activate the vagus. Energetic singing activates both your sympathetic nervous system and vagus nerve, which helps to get into a flow state [1].
Singing in unison, which is often done in churches and synagogues, also increases HRV and vagus function [1].
Singing has been found to increase oxytocin [17].
3. Yoga
Yoga increases vagus nerve and parasympathetic system activity in general [18, 19].
A 12-week yoga intervention was associated with greater improvements in mood and anxiety than a control group who did walking exercises. The study found increased thalamic GABA levels, which are associated with improved mood and decreased anxiety [18].
4. Meditation
There are two types of meditation that can stimulate the vagus nerve.
Loving-kindness meditation increases vagal tone, as measured by heart rate variability.
Also, Om chanting stimulates the vagus nerve [20].
5. Positive Social Relationships
In a study, participants were instructed to sit and think compassionately about others by silently repeating phrases like “May you feel safe, may you feel happy, may you feel healthy, may you live with ease,” and keep returning to these thoughts when their minds wandered.
Compared to the controls, the meditators showed an overall increase in positive emotions, like joy, interest, amusement, serenity, and hope after the class. These emotional and psychological changes were correlated with a greater sense of connectedness to others and to an improvement in vagal function, as seen by heart-rate variability.
Simply meditating, however, didn’t always result in a more toned vagus nerve. The change only occurred in meditators who became happier and felt more socially connected. Those who meditated just as much but didn’t report feeling any closer to others showed no change in the tone of the vagus nerve.
6. Breathe Deeply and Slowly
Deep and slow breathing stimulates the vagus nerve.
Your heart and neck contain neurons that have receptors called “baroreceptors.”
These specialized neurons detect your blood pressure and transmit the neuronal signal to your brain (NTS), which goes on to activate your vagus nerve that connects to your heart to lower blood pressure and heart rate. The result is a lower fight-or-flight activation (sympathetic) and more rest-and-digest (parasympathetic).
Baroreceptors can be variably sensitive. The more sensitive they are, the more likely they are going to fire and tell your brain that the blood pressure is too high and it’s time to activate the vagus nerve to lower it.
Slow breathing, with a roughly equal amount of time breathing in and out, increases the sensitivity of baroreceptors and vagal activation, which lowers blood pressure and reduces anxiety by reducing your sympathetic nervous system and increasing your parasympathetic system [21].
For an average adult, breathing around 5-6 breaths per minute can be very helpful.
Tip: You need to breathe from your belly and slowly. That means when you breathe in, your belly should expand or go out. When you breathe out your belly should cave in. The more your belly expands and the more it caves in, the deeper you’re breathing.
7. Laughter
As the saying goes, laughter is the best medicine. Many studies show the health benefits of laughing [22].
It seems like laughter is capable of stimulating the vagus nerve.
A study done on yoga laughter found increased HRV (heart rate variability) in the laughter group [23].
There are various case reports of people fainting from laughter, which may be from the vagus nerve/parasympathetic system being stimulated too much.
For example, fainting can come after laughter, urination, coughing, swallowing, or bowel movements, all of which are helped along by vagus activation [24].
There are case reports of people passing out from laughter who have a rare syndrome (Angelman’s) that’s associated with increased vagus stimulation [25, 26].
Laughter is also sometimes a side effect of vagus nerve stimulation [13].
A good bout of laughter is good for cognitive function and protects against heart disease [22]. It also increases beta-endorphins and nitric oxide and benefits the vascular system [27].
8. Prayer
Studies have shown that reciting the rosary prayer increases vagus activation. Specifically, it enhances cardiovascular rhythms such as diastolic blood pressure and HRV [28].
Studies also found that the reading of one cycle of the rosary takes approximately 10 seconds and thus causes readers to breathe at 10-second intervals (includes both in and out breath), which increases HRV and therefore vagus function [1].
9. PEMF
Magnetic fields are capable of stimulating the vagus nerve. Studies have found that PEMF can increase heart rate variability and increase vagus stimulation [29].
I use a pulsed magnetic stimulator called ICES in my gut and brain, which stimulates my vagus nerve increasing my appetite and stimulating me.
I recommend using this in your gut, brain, and side of your neck. My gut flow increases and inflammation is reduced everywhere when I put this on my gut.
At first, I didn’t understand how it can have systemic effects if I placed it on my gut, but the vagus nerve must be the main reason given that it’s stimulated by magnets.
10. Breathing Exercises
Breathing in and out with resistance will likely stimulate your vagus nerve better –kind of like jogging with a backpack.
A breathing exercise is to breathe out as hard as you can until it’s really uncomfortable and until you notice how awake you are. I haven’t seen studies on this, but I suspect it will help with your vagus nerve.
11. Probiotics
The guts nervous system connects to the brain through the vagus nerve. There is increasing evidence pointing to an effect of the gut microbiota on the brain.
Animals supplemented with the probiotic Lactobacillus rhamnosus experienced various positive changes in GABA receptors mediated by the vagus nerve [30].
12. Exercise
Mild exercise stimulates gut flow. This is mediated by the vagus nerve, which means that exercise also stimulates it [6].
13. Massage
Massaging certain areas like your carotid sinus (located on your neck) can stimulate the vagus nerve. This helps reduce seizures [31].
A pressure massage can activate the vagus nerve. These massages help infants gain weight by stimulating the gut and this is largely mediated by vagus nerve activation [32, 33].
Foot massages can also increase vagal activity and heart rate variability, while lower your heart rate and blood pressure [34].
All of these decrease heart disease risk.
14. Fasting
Intermittent fasting and reducing calories both increase high-frequency heart rate variability in animals, which is a marker of vagal tone [35].
Indeed, many anecdotal reports show that intermittent fasting benefits heart rate variability.
When you fast, part of the decrease in metabolism is mediated by the vagus nerve. Specifically, the vagus detects a decline in blood glucose and a decrease of mechanical and chemical stimuli from the gut. This increases the vagus impulses from the liver to the brain (NTS), which slows the metabolic rate [36].
Hormones such as NPY increase while CCK and CRH decrease during fasting [36].
When we eat, the opposite happens. Satiety-related stimulatory signals from the gut contribute to increased sympathetic activity and stress-responsiveness (higher CRH, CCK, and lower NPY) [36].
Fasting can increase the activity in the subdiaphragmatic vagus, which can increase an unfavorable sensitivity to pain in animals [37].
The vagus nerve may make you more sensitive to estrogen. In female rats, fasting increases the number of estrogen receptors in certain parts of the brain (NTS and PVN) by the vagus nerve [38].
Also, I’m not sure about all 30 ways to stimulate your vagus nerve, although some of them seem quite reasonable and easy to try. I do think your body’s own wisdom can guide you in the right direction, and certainly am having some of the symptoms. There are so many systems operating inside our physical body, that when one thing gets out of whack, it can affect many other areas of function. And, I’m long past not trusting our current mainstream medical system to figure anything out (I hope I don’t get in trouble for saying that).
30 Ways to Stimulate Your Vagus Nerve + Functions & Disorders
By Joe Cohen, BS Last updated: May 31, 2019
https://selfhacked.com/blog/32-ways-to- ... -about-it/" onclick="window.open(this.href);return false;
The vagus nerve is critical to optimal health, no matter what your issues are. In this post, we will tell you how to stimulate it, and how it affects your health.
What is the Vagus Nerve and Its Function?
In people with fatigue, food sensitivities, anxiety, gut problems, brain fog, and depersonalization, the vagus nerve is almost always at play. These people have lower vagal tone, which means it has a lower ability to perform its functions.
The only question is which aspect of the vagus nerve is malfunctioning and to what extent it is the problem vs. other aspects of your biology.
The vagus nerve is part of the parasympathetic nervous system, referred to as the rest-and-digest system. It’s not the only nerve in the parasympathetic system, but it’s by far the most important one because it has the most far-reaching effects.
The word vagus means “wanderer,” because it wanders all over the body to various important organs.
The vagus nerve affects the brain, gut (intestines, stomach), heart, liver, pancreas, gallbladder, kidney, ureter, spleen, lungs, reproductive organs (female), neck (pharynx, larynx, and esophagus), ears, and tongue.
Given the importance of the vagus nerve to the gut (and other organs), when it’s not working properly, it will cause digestive disorders including dyspepsia, gastroparesis, GERD, ulcerative colitis, anorexia, and bulimia, to name a few.
How It Affects Your Body
Brain
In the brain, the vagus nerve helps mood and controls anxiety and depression.
The vagus nerve is largely responsible for the mind-body connection since it goes to all the major organs (except the adrenal and thyroid glands).
It’s intimately tied to how we connect with one another — it links directly to nerves that tune our ears to human speech, coordinate eye contact, and regulate emotional expressions. It influences the release of oxytocin, a hormone that is important in social bonding [1].
Studies have found that higher vagal tone is associated with greater closeness to others and more altruistic behavior [2].
Vagus activity of a child can be affected by their mother. Infants had lower vagus activity with mothers who were depressed, angry, or anxious during pregnancy [3].
Some studies suggested that the vagus nerve is important for getting in the mental state of “flow”. It’s believed that the combination of sympathetic (fight-or-flight) and vagus activation creates the right environment for a flow state [1].
Vagus nerve stimulation might increase wakefulness (by increasing orexin in the prefrontal cortex). It has been shown to decrease the amounts of daytime sleep and rapid eye movement in epilepsy patients with traumatic brain injury and also promoted the recovery of consciousness in comatose rats after traumatic brain injury [4].
However, the vagus nerve also might cause ‘sickness behavior’ (fatigue, sleepiness, depression, anxiety, appetite loss, pain, lowered motivation, and failure to concentrate) in an inflammatory state (IL-1b) [5].
Gut
In the gut, it increases stomach acidity, digestive juice secretion, and gut flow. Since the vagus nerve is important for increasing gut flow (motility), having less vagus activation will increase your IBS risk, which is a result of slower flow [6].
Stimulating the vagus nerve increases the release of histamine by stomach cells, which helps release stomach acid [7]. So, low stomach acidity is usually, in part, a vagus nerve problem. By releasing intrinsic factor, the vagus nerve is important to help you absorb vitamin B12.
Satiety and relaxation following a meal are in part caused by activation of the vagus nerve’s transmission to the brain in response to food intake [8].
The vagus nerve is important in conditions like GERD, not only because it controls stomach acidity, but also because it controls the esophagus.
Heart
In the heart, it controls heart rate and blood pressure. Vagus activation will lower the risk of heart disease, among other lethal diseases [9].
Liver, Pancreas, and Gallbladder
In the liver and pancreas, it helps control blood glucose balance.
In the gallbladder, it helps release bile, which can help you get rid of toxins and break down fat.
Kidney and Bladder
The vagus nerve promotes general kidney function. It helps with glucose control and increases blood flow, which improves blood filtration. Vagus activation also releases dopamine in the kidneys, which helps excrete sodium and, thereby, lower blood pressure [10, 11].
The vagus nerve also goes to the bladder. A side effect of its stimulation is urinary retention, which means that less vagus stimulation can cause you to urinate frequently. Indeed, many of my clients complain about frequent urination (also due to low vasopressin, low aldosterone, and high cortisol) [12, 13].
Spleen
In the spleen, it can reduce inflammation. Note that vagus activation will reduce inflammation in all target organs (by releasing acetylcholine), but when it activates in the spleen the response will probably be more systemic [14].
It helps control fertility and orgasms in women by connecting to the cervix, uterus, and vagina. Women can actually experience orgasms simply from the vagus nerve.
Mouth and Ears
In the tongue, it helps control taste and saliva; while in the eyes, it helps release tears.
The vagus nerve explains why a person may cough when tickled on the ear, such as when trying to remove ear wax with a cotton swab.
Vagus nerve stimulation helps people with tinnitus because of its connection to the ear.
30 Ways to Stimulate the Vagus Nerve
1. Cold
Studies show that when your body adjusts to cold, your fight-or-flight (sympathetic) system declines and your rest-and-digest (parasympathetic) system increases, which is mediated by the vagus nerve [15].
Any kind of acute cold exposure will increase vagus nerve activation [16].
You can dip your face in cold water to start. I’ve graduated and now take fully cold showers, expose myself to cold, and drink cold water.
2. Singing or Chanting
Singing increases Heart Rate Variability (HRV) [1].
Humming, mantra chanting, hymn singing, and upbeat energetic singing all increase HRV in slightly different ways [1].
I do Om chanting in my infrared sauna.
Singing initiates the work of a vagal pump, sending relaxing waves through the choir [1].
Singing at the top of your lungs works the muscles in the back of the throat to activate the vagus. Energetic singing activates both your sympathetic nervous system and vagus nerve, which helps to get into a flow state [1].
Singing in unison, which is often done in churches and synagogues, also increases HRV and vagus function [1].
Singing has been found to increase oxytocin [17].
3. Yoga
Yoga increases vagus nerve and parasympathetic system activity in general [18, 19].
A 12-week yoga intervention was associated with greater improvements in mood and anxiety than a control group who did walking exercises. The study found increased thalamic GABA levels, which are associated with improved mood and decreased anxiety [18].
4. Meditation
There are two types of meditation that can stimulate the vagus nerve.
Loving-kindness meditation increases vagal tone, as measured by heart rate variability.
Also, Om chanting stimulates the vagus nerve [20].
5. Positive Social Relationships
In a study, participants were instructed to sit and think compassionately about others by silently repeating phrases like “May you feel safe, may you feel happy, may you feel healthy, may you live with ease,” and keep returning to these thoughts when their minds wandered.
Compared to the controls, the meditators showed an overall increase in positive emotions, like joy, interest, amusement, serenity, and hope after the class. These emotional and psychological changes were correlated with a greater sense of connectedness to others and to an improvement in vagal function, as seen by heart-rate variability.
Simply meditating, however, didn’t always result in a more toned vagus nerve. The change only occurred in meditators who became happier and felt more socially connected. Those who meditated just as much but didn’t report feeling any closer to others showed no change in the tone of the vagus nerve.
6. Breathe Deeply and Slowly
Deep and slow breathing stimulates the vagus nerve.
Your heart and neck contain neurons that have receptors called “baroreceptors.”
These specialized neurons detect your blood pressure and transmit the neuronal signal to your brain (NTS), which goes on to activate your vagus nerve that connects to your heart to lower blood pressure and heart rate. The result is a lower fight-or-flight activation (sympathetic) and more rest-and-digest (parasympathetic).
Baroreceptors can be variably sensitive. The more sensitive they are, the more likely they are going to fire and tell your brain that the blood pressure is too high and it’s time to activate the vagus nerve to lower it.
Slow breathing, with a roughly equal amount of time breathing in and out, increases the sensitivity of baroreceptors and vagal activation, which lowers blood pressure and reduces anxiety by reducing your sympathetic nervous system and increasing your parasympathetic system [21].
For an average adult, breathing around 5-6 breaths per minute can be very helpful.
Tip: You need to breathe from your belly and slowly. That means when you breathe in, your belly should expand or go out. When you breathe out your belly should cave in. The more your belly expands and the more it caves in, the deeper you’re breathing.
7. Laughter
As the saying goes, laughter is the best medicine. Many studies show the health benefits of laughing [22].
It seems like laughter is capable of stimulating the vagus nerve.
A study done on yoga laughter found increased HRV (heart rate variability) in the laughter group [23].
There are various case reports of people fainting from laughter, which may be from the vagus nerve/parasympathetic system being stimulated too much.
For example, fainting can come after laughter, urination, coughing, swallowing, or bowel movements, all of which are helped along by vagus activation [24].
There are case reports of people passing out from laughter who have a rare syndrome (Angelman’s) that’s associated with increased vagus stimulation [25, 26].
Laughter is also sometimes a side effect of vagus nerve stimulation [13].
A good bout of laughter is good for cognitive function and protects against heart disease [22]. It also increases beta-endorphins and nitric oxide and benefits the vascular system [27].
8. Prayer
Studies have shown that reciting the rosary prayer increases vagus activation. Specifically, it enhances cardiovascular rhythms such as diastolic blood pressure and HRV [28].
Studies also found that the reading of one cycle of the rosary takes approximately 10 seconds and thus causes readers to breathe at 10-second intervals (includes both in and out breath), which increases HRV and therefore vagus function [1].
9. PEMF
Magnetic fields are capable of stimulating the vagus nerve. Studies have found that PEMF can increase heart rate variability and increase vagus stimulation [29].
I use a pulsed magnetic stimulator called ICES in my gut and brain, which stimulates my vagus nerve increasing my appetite and stimulating me.
I recommend using this in your gut, brain, and side of your neck. My gut flow increases and inflammation is reduced everywhere when I put this on my gut.
At first, I didn’t understand how it can have systemic effects if I placed it on my gut, but the vagus nerve must be the main reason given that it’s stimulated by magnets.
10. Breathing Exercises
Breathing in and out with resistance will likely stimulate your vagus nerve better –kind of like jogging with a backpack.
A breathing exercise is to breathe out as hard as you can until it’s really uncomfortable and until you notice how awake you are. I haven’t seen studies on this, but I suspect it will help with your vagus nerve.
11. Probiotics
The guts nervous system connects to the brain through the vagus nerve. There is increasing evidence pointing to an effect of the gut microbiota on the brain.
Animals supplemented with the probiotic Lactobacillus rhamnosus experienced various positive changes in GABA receptors mediated by the vagus nerve [30].
12. Exercise
Mild exercise stimulates gut flow. This is mediated by the vagus nerve, which means that exercise also stimulates it [6].
13. Massage
Massaging certain areas like your carotid sinus (located on your neck) can stimulate the vagus nerve. This helps reduce seizures [31].
A pressure massage can activate the vagus nerve. These massages help infants gain weight by stimulating the gut and this is largely mediated by vagus nerve activation [32, 33].
Foot massages can also increase vagal activity and heart rate variability, while lower your heart rate and blood pressure [34].
All of these decrease heart disease risk.
14. Fasting
Intermittent fasting and reducing calories both increase high-frequency heart rate variability in animals, which is a marker of vagal tone [35].
Indeed, many anecdotal reports show that intermittent fasting benefits heart rate variability.
When you fast, part of the decrease in metabolism is mediated by the vagus nerve. Specifically, the vagus detects a decline in blood glucose and a decrease of mechanical and chemical stimuli from the gut. This increases the vagus impulses from the liver to the brain (NTS), which slows the metabolic rate [36].
Hormones such as NPY increase while CCK and CRH decrease during fasting [36].
When we eat, the opposite happens. Satiety-related stimulatory signals from the gut contribute to increased sympathetic activity and stress-responsiveness (higher CRH, CCK, and lower NPY) [36].
Fasting can increase the activity in the subdiaphragmatic vagus, which can increase an unfavorable sensitivity to pain in animals [37].
The vagus nerve may make you more sensitive to estrogen. In female rats, fasting increases the number of estrogen receptors in certain parts of the brain (NTS and PVN) by the vagus nerve [38].