When we talk about stressful situations, we often use metaphors related to the digestive system — we’ve all had “butterflies in our stomach” or had to make a “gut-wrenching” decision. And the fact is, there are more nerve cells in your gut than your entire spinal cord. So it’s only natural that your digestive system should be susceptible to environmental stressors.
But what’s actually taking place in our bodies when we have these feelings? Keep reading to find out.
The human nervous system is highly complex, with many subdivisions that regulate different parts of your behavior.
Your nervous system’s two primary parts are the central nervous system and the peripheral nervous system. The central nervous system includes your brain and spinal cord, and the peripheral nervous system consists of all of the nerves that branch out from the brain and spinal cord and extend to other parts of the body, like muscles and organs.
The peripheral nervous system is also divided into two parts: the somatic nervous system, which regulates the senses and voluntary muscle movement, and the autonomic nervous system, which controls involuntary body functions like blood flow, heartbeat, breathing, and digestion.
The autonomic nervous system has three parts: the sympathetic nervous system (SNS), the parasympathetic nervous system (PNS), and the enteric nervous system (ENS). The SNS and PNS interact to regulate your body's reaction to external threats, while the ENS regulates digestion.
When you are in a stressful or potentially threatening situation, your sympathetic nervous system responds by releasing a stress hormone, cortisol, and triggering a "fight or flight” response. This stress response triggers physiological responses that help you deal with the perceived threat: your breathing, heart rate, and metabolism accelerate; more blood flows to your muscles; you sweat more; and your pupils dilate.
When the threat has passed, your parasympathetic nervous system kicks in and returns your body to a normal resting state.
In addition to stress symptoms, the fight-or-flight response also causes the enteric nervous system to slow down so the body can divert more energy to deal with the perceived threat. That can lead to stomach pains, indigestion, heartburn, and nausea.
Stress can also interrupt your body’s gastrointestinal peristalsis or, in other words, your gut’s motility. This natural wave-like contraction and relaxation of the digestive tract's muscles pushes food from the esophagus to the stomach, intestinal tract, and rectum.
Stress responses can cause the digestive tract muscles to spasm, leading to a lack of appetite, irritation, diarrhea, or constipation.
The ENS contains more than 100 million neurons and extends along the entire digestive tract from the esophagus, through the stomach and intestines, down to the rectum and anus.
Researchers sometimes call the ENS our “second brain” because it relies on the same type of neurons and neurotransmitters found in the central nervous system. It also functions independently from the rest of the nervous system through local reflex activity to control the digestive functions of muscle contraction and relaxation, secretion and absorption, and blood flow.
But although it can technically function on its own, the ENS constantly interacts with the rest of the nervous system. The relationship between the gastrointestinal (GI) tract and the central nervous system — our body’s would-be gut-brain axis, a highly receptive, emotionally sensitive superhighway — is the focus of much new and exciting research. And we’re learning more about how stress can cause gastrointestinal dysfunction, which can then cause more stress, in a troublesome feedback loop.
In the body’s gastrointestinal tract resides a complex and thriving community of microorganisms collectively known as the “gut microbiome”or “gut flora.” It helps us digest our food, supports our immune system, and may even regulate hormones and neurotransmitters in the ENS. (Learn more about gut health.)
But how does stress affect the bacteria in the gut microbiome?
Recent studies suggest that stress and depression can overstimulate the autonomic nervous system, releasing stress hormones and causing inflammation. That, in turn, causes bacteria in the microbiome to release metabolites, toxins, and hormones that can alter your mood and eating behavior. And that can further destabilize the microbiome and reduce the numbers of helpful bacteria in the gut.
It’s no secret that chronic stress causes an overstimulation of the autonomic nervous system and can adversely affect the body.
We’ve seen the effects of short-term stress and the fight-or-flight response on the digestive system. But what about long-term stress?
Here’s a breakdown of the potential effects of short- and long-term stress on the digestive system:
• Loss of appetite
• Abdominal pain
• Imbalance in the gut microbiome
• Irritable bowel syndrome (IBS)
• Aggravation of peptic ulcers
• Gastroesophageal reflux disease (GERD)
While there’s little doubt that psychological stress exacerbates the symptoms of gastrointestinal diseases, direct causality hasn't been proven in most cases. However, functional gastrointestinal disorders (FGIDs) — like irritable bowel syndrome (IBS) and functional dyspepsia — are a slightly different story.
FGIDs are digestive problems with no apparent physical cause, like tumors or chemical imbalances. They generally affect gut motility and sensation and interfere with the gut-brain axis. FGIDs are extremely common — nearly 25 million Americans suffer from some form of FGID.
Probably not. While some studies suggest the overstimulation of the autonomic nervous system caused by stress might increase the perception of IBS symptoms, it's not generally believed to be a causal factor.
However, some studies suggest an indirect link between the two, as IBS can be triggered by an immune system response, which can be affected by stress or anxiety.
Yes. Again, the sympathetic nervous system’s fight-or-flight response can cause an interruption to gastrointestinal peristalsis, which can lead to mild, short-term diarrhea.
It depends. Stress can cause spasms in the esophagus, which can cause acid from the stomach to flow back up into the esophagus and cause irritation.
However, it's unlikely that stress triggers the increase in the production of stomach acid associated with gastroesophageal reflux disease (GERD). In most cases, stress increases the perception of — and sensitivity to — GERD symptoms.
Probably not. Although many once believed that stress caused ulcers, recent studies point to bacterial infection as the culprit.
However, some researchers have suggested stress may disturb the balance of hydrochloric acid and protective secretions in the stomach, making it more vulnerable to ulcers.
No. IBDs, like ulcerative colitis and Crohn’s disease, are not caused by stress. However, stress can intensify symptoms.
Stress can often lead to a craving for highly palatable foods, further aggravating IBS and acid reflux symptoms. It can also cause diarrhea or constipation and disturb the balance of the gut microbiome.
If you’re feeling stressed or experiencing gastrointestinal discomfort, you should avoid foods you know will cause more irritation. Keeping a food diary can help identify the culprits.
In general, you should stay away from foods that are spicy, greasy, or high in fat or acid. With beverages, avoid carbonated sodas, caffeine, and alcohol. Too much dairy can also wreak havoc in your gut, even if you aren't lactose intolerant.
On the other hand, certain foods have been shown to reduce anxiety. Foods that contain omega-3 fatty acids — like some fish, nuts, and seeds — are natural mood boosters. Magnesium — found in almonds — helps manage cortisol levels, and vitamin C in citrus lowers blood pressure. High-fiber foods can sometimes help, but not always. Probiotics help support a healthy gut microbiome.
You can take many different approaches to reducing stress, some focusing on physical health and others on mental health. (Get many tips for reducing stress in this recent blog post.)
Here are a few of the most common options for managing stress:
• Regular exercise
• Healthy eating
• Cognitive-behavioral therapy
• Relaxation practices like meditation and yoga
• Gut-directed hypnotherapy
If you have recurring digestive issues or want to know more about your digestive health, a good first step is to talk to your primary care provider about your symptoms and concerns. They can help you identify necessary diet or lifestyle changes and refer you to a specialist if necessary.
Looking for a partner to help you reach your health goals? Carbon Health has compassionate healthcare providers ready to talk with you today about all your health needs.
Carbon Health’s medical content is reviewed and approved by healthcare professionals before it is published, but it is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Talk to your healthcare provider about questions you may have regarding your health or a medical condition, and before making changes to your healthcare routine.