Stress and the Gut

Lesson objective:

In this lesson, we learn about the gastrointestinal system and how sensitive it is towards emotional distress and chronic stress.

We’re going to continue our tour through the body, exploring now how stress affects nearly every major system in the body. 

When we talked about interoception, we discussed how some emotions are sensed first as sensations in different parts of our bodies and how these sensations may differ from an individual to another. 

Not everyone experiences a tightness in their chest when nervous, and not everyone has a racing heart when they feel a sense of love. 


But generally, and for a lot of people, feelings like fear, stress, or even excitement, are felt in the stomach. 

The gastrointestinal system is very sensitive to emotion and stress.  

Anger, anxiety, sadness, joy – all of these feelings can trigger sensations in the stomach and gut area. 

Perhaps you have heard people talk about being “nauseous with fear,” full of “butterflies in the stomach” before an expected encounter. 

In general, the stomach is tied to emotion states. 

This is, in part, because there is a direct relationship between the stomach and your brain via the autonomic nervous system, and the vagus nerve in particular. This network, the “gut-brain” network, is in constant communication.

For example, this communication network informs you when you are hungry or full. But this network can also be used to send a signal to your body that you are in danger. 

Earlier, we talked about the relationship between the brain and the parasympathetic nervous system. The parasympathetic nervous system includes nerves and signals to your digestive tract and is used to send signals of “resting and digesting” to your gastrointestinal system. The sympathetic nervous system, on the other hand, constricts and disrupts the digestion process. In other words, when you are in situations of high stress, your sympathetic, rather than parasympathetic system is activated and thus puts a “pause” on healthy digestion, waiting instead for the stress to pass. 


During the stress response, your brain signals to your stomach that there is trouble. That there is some threat. It signals to your entire digestive system, from your esophagus to your intestines that something dangerous is coming. As part of this process, the heart reduces blood flow to gastrointestinal organs, sending it instead to other organs and muscles vital to the “fight or flight” response. This alteration in blood flow can perpetuate feelings of nausea or pain in the stomach. 

Reduced blood flow to your gastrointestinal tract drastically slows your metabolism. Less blood leads to less activity, and less absorption of nutrients from food. Overall, in times of threat, digestion and nutrient absorption are not as “important” as fighting or fleeing. Remember, in times of stress, the brain prioritizes core survival functions in the moment. And as such, organs and muscles more critical to fight or flight responses receive extra blood and oxygen. 

Beyond metabolism and blood flow, stress can cause your esophagus muscles to go into spasms and can lead to hypersensitivity to swallowing and esophageal movements. 

It may also increase the acid in your stomach, resulting in indigestion or exaggerated symptoms of acid reflux, both of which can make you feel very nauseous. 

Lastly, as the stress response shifts attention away from digestion, your digestive tract produces fewer enzymes, damaging the environment for healthy bacteria, which are critical for healthy waste removal. In a short amount of time, then, the colon becomes less functional, resulting in either diarrhea or constipation. And cumulatively, these gastrointestinal disruptions can themselves produce more feelings of stress and anxiety, exacerbating the effects of stress in an unhealthy cycle.