The Sensitive Gut

• Inside the gut
  • The digestive journey
  • The aging GI tract
• The stress connection
  • The second brain
  • Stress and the functional GI disorders
  • Treating the whole body
  • Antidepressants for body and mind
• Gastroesophageal reflux disease
  • Causes of GERD
  • Diagnosing reflux
  • Complications of reflux
  • Self-help for reflux
  • Antireflux drug therapy
  • Herbal remedies
  • Surgical options for reflux
• Functional dyspepsia
  • Diagnosing FD
  • Tests and medication
  • Causes of FD
  • Treating FD
• Irritable bowel syndrome
  • What is IBS?
  • Causes of IBS
  • Diagnosing IBS
  • Managing IBS
• Constipation
  • How constipation happens
  • Frequency of bowel movements: What’s normal?
  • Causes of constipation
  • Diagnosing constipation
  • Treating constipation
• Diarrhea
  • What is diarrhea?
  • Causes of diarrhea
  • When to call the doctor
  • Diagnosing diarrhea
  • Treating diarrhea
  • Preventing diarrhea
• Excessive gas
  • Where does gas come from?
  • A gas primer
  • Diagnosing and treating aerophagia and flatus
  • Treating belching
  • Treating flatulence
• Resources

Have you ever had a “gut-wrenching” experience? Do certain situations make you “feel nauseous”? Have you ever felt “butterflies” in your stomach? We use these expressions to describe emotional reactions because the gastrointestinal tract is sensitive to emotion. Anger, anxiety, sadness, elation: All of these emotions and many others can trigger symptoms in the gut.

The brain has a direct effect on the stomach: Even the thought of eating can release the stomach’s juices before food gets there. This connection goes both ways. A troubled intestine can send signals to the brain, just as a troubled brain can send signals to the gut. A patient’s distressed gut can be as much the cause as the product of anxiety, stress, or depression. That’s because the brain and the gastrointestinal system are intimately connected. So intimately, says Dr. Douglas Drossman, co-director of the University of North Carolina’s Center for Functional GI and Motility Disorders, that they should be viewed as one system, rather than two.

This is especially true in cases when the gut is acting up and there’s no obvious physical or infectious cause. For such functional GI disorders, trying to heal a distressed gut without considering the impact of stress and emotion is like trying to improve an employee’s poor job performance without considering his manager and work environment.

The second brain

To appreciate the impact of stress on the gut, it is helpful to understand the similarities and connections between the brain and the digestive system. The gut is controlled by the enteric nervous system (ENS), a complex system of about 100 million nerves that oversees every aspect of digestion. The ENS is heavily influenced by the central nervous system (CNS) with which it communicates through pathways of nerves. The “second brain,” as the ENS is sometimes called, arises from the same tissues as the CNS during fetal development. It has many structural and chemical counterparts in the cranial brain, including sensory and motor neurons as well as glial cells, which support and protect the neurons. And the ENS uses many of the same neurotransmitters, or chemical messengers, as the CNS.

The ENS is embedded in the gut wall and participates in a rich dialogue with the brain during the entire journey of food through the 30-foot-long digestive tract. The ENS cells in the lining of the gut communicate with the brain by way of the autonomic nervous system, which controls the body’s vital functions. As part of that system, sympathetic nerves connect the gut to the spinal cord and then to the base of the brain. In addition, parasympathetic nerves pass to and from the base of the brain via the vagus nerve from the upper gut or the sacral nerves from the colon. The gut and brain use their shared neurotransmitters, including acetylcholine and serotonin, to transmit information back and forth by way of the sympathetic and parasympathetic nerves.

This two-way communication system between the gut and the brain explains why you stop eating when you’re full (sensory neurons in your gut let your brain know that your stomach is distended), or conversely, why anxiety over this morning’s exam has ruined your appetite for breakfast (the stress activated your “fight or flight” sympathetic nervous system, inhibiting gastrointestinal secretion and reducing blood flow to the gut).