The word "vagus" is Latin, and translates to "wandering". The vagus nerve is the 10th cranial nerve that connects the gut to the brain - branching (or wandering) into many of our organs that fall between the two - and is the longest nerve in our body. Gut feeling Gut instinct Gut reaction Trust your gut There is some meaning behind these phrases... This is why I called my supplement company "Vagus Nutrition"! This summary will be detailed, but also simplified to only what is is necessary - so come with a fresh pair of eyes! It must just blow your mind... The sympathetic nervous system (SNS) is in charge of winding you up, "fight or flight" mode. This includes the release of cortisol and adrenaline and also entails moving blood from what's not "essential" (what's not needed when running away from a lion, if you think about it evolutionarily), like the digestive system. So to repeat that, when your body is winding up or stressed, blood is taken away from the digestive system (so it doesn't function well) because the body is flooding it to your muscles. The parasympathetic nervous system (PNS) is in charge of winding us down, "rest and digest" mode - the vagus nerve makes up 75% of it's fibres. This includes the release of acetylcholine (regulates heart rate and blood pressure, intestinal peristalsis [what moves food through your intestines], glandular secretion, etc. (source)). It's also what helps you recover! So again to repeat that, the PNS (and the vagus nerve) slows you down; decreasing heart rate, slowing breathing rate, stimulating digestion, regulating the immune system, reducing inflammation, balancing hormones, etc. - hence the importance of it for gut health! Both are part of the autonomic nervous system (ANS) that regulates our organs and helps us to maintain the correct stress state. Problems with any of these organs can affect the ANS, and vice versa - information is bi-directional (flows both ways), so when one is unhealthy the other is effected.
Now, to zoom in on the vagus nerve. In simple terms it's a communication line between the gut, the brain, and many of the organs in between. The vagus nerve collects loads of information from your organs and tells the body how to react. This includes telling the stomach to secrete stomach acid, and the pancreas to make enzymes. If ineffective this can lead to cramping and diarrhea if food isn't absorbed OR constipation if intestinal peristalsis is affected OR fatigue/other issues from not absorbing nutrients in food. The function of your vagus nerve is described as "vagal tone". Good vagus nerve = high vagal tone. And a simple indication of your vagal tone is your heart rate/breathing. Short-shallow breathes = low vagal tone. Another indication is your ability to be calm. If you struggle to wind down, you may have low vagal tone. Other signs of damage to the vagal nerve (low vagal tone) are difficulty swallowing, hoarseness of voice, poor gag reflex, and of course... gut issues! On the positive side, a healthy vagus nerve can increase blood sugar regulation, reduced risk of stroke/cardiovascular disease, lower blood pressure, improve digestion, better mood, less anxiety, and more stress resilience. (source / source) What can you do to change your vagal tone? 1. Cold water - this actives the Mammalian Drive Reflex (prime) which is designed slow our body down when diving into water 2. Using your voice - like when yogi's say om... chanting, singing, laughing, gargling, all active your vagus nerve 3. Breathing slower and deeper 4. Long steady walks - calms the nervous system 5. Supplements: Potassium, sodium, and magnesium (on the other hand, for the SNS: phosphorus and calcium) 6. Acupuncture 7. Yoga - trains you to stay calm and control your breathing during the stress of holding positions In addition, your body cannot sustain sympathetic activation (the release of adrenaline, cortisol, etc.) - that "fight or flight" stress state - and in a relentless world of stimulation and stress, this can so often happen. So the final point to take away with you, reduce and manage your day-to-day stress, and allow yourself time to wind down - especially in the hour surrounding eating. Upcoming book recommendations that are on my list: Activate your vagus nerve The vagus code Accessing the healing power of the vagus nerve