The Brain in Your Gut — A Mind of Its Own
By Mary Kaye Sawyer-Morse, PhD, RD
Today’s Dietitian
Vol. 7 No. 5 P. 26

Listen to what your gut tells you. Structurally and neurochemically, the enteric nervous system is a complex brain in its own right.

You know the feeling. The hairs on the back of your neck tingle and your stomach tightens. Call it a gut reaction, gut instinct, or a gut-wrenching experience. You just know something without really knowing why. Your gut is communicating and you better listen. Isn’t it interesting how often your gut accurately reflects how you feel? It seems to know you better than you know yourself!

A Closer Look
The gut, at first glance, doesn’t seem especially smart. It is a 30-foot-long tube that begins at the mouth and ends at the rectum. But consider the job it performs. The gut is the gatekeeper of the body, deciding what to allow into our bodies and what to keep out. When it is working well, the intestinal lining prevents molecules that are too big or too toxic from entering the body. The gut literally integrates the outside world into our cells. In addition, the gut serves as a barometer for our overall emotional and physical states. The gut is smarter than you think.

We now know that neuropeptides once believed to exist exclusively in the nervous system are also found in the gut. Finding these neuropeptides—serotonin and endorphins that impact emotions and thinking—in the gut suggest that it, too, has the capacity to think and feel, although in a different manner than the brain. Hence, your “gut” feelings are not a figment of imagination but rather a physical phenomenon. In fact, research has demonstrated that emotions such as anger, stress, and fear can have a significant impact on the biochemistry and function of the gut. At an extreme, anger has been shown to kill off “friendly” bacteria in the gastrointestinal (GI) tract, thereby creating an ecological imbalance.1,2 Negative emotions affect gut health in other ways as well. For example, acute stress may alter the production of stomach acid (it can either increase or decrease it), which in turn can cause indigestion. Severe or long-term stress can induce long-term alteration in the stress response impacting multiple stress hormones. This biochemical alteration may in turn affect colonic motor activity and gastric emptying as well as alter intestinal permeability and increase susceptibility to colonic inflammation.2,3,4 On the other hand, happiness and relaxation have been shown to reduce colonic motility and perception of gastric distress.5

That’s a lot to stomach.

The Gut as a Neurological Organ
The gut is the only organ that contains an intrinsic nervous system with an ability to mediate reflexes in the complete absence of input from the brain or spinal cord. Why would this be? Apparently, as humankind evolved, we developed a brain in the head as well as a gut with a mind of its own. The “mind” in the gut may actually be a vestigial brain dating back hundreds of millions of years to when life first evolved. The job, so to speak, of this ancient system was to ensure that the important tasks of eating and assimilating nutrients were efficiently performed—freeing the other “brain” to accomplish equally important tasks such as obtaining food and escaping danger. Over the millennia, the brain above the neck evolved while the mind in the gut remained an independent system. Today, the gut is an elaborate data-processing center that enables the human body to accomplish life-sustaining tasks with little mental effort. Nonetheless, let things go awry and you’re left with an inefficient gut with an attitude.

The gut is referred to as a neurological organ to emphasize the particular importance of the nervous system in the regulation of digestive functions. Virtually each aspect of digestive activity is under the regulatory influence of neurons, among which the enteric nervous system (ENS) plays the most important part. The gut’s own nervous system, the ENS acts like a brain that functions independently of the central nervous system. The ENS is composed of more than 100 million nerve cells, a number roughly equal to the number of nerve cells in the spinal cord. Add to this number the nerve cells of the esophagus, stomach, and large intestine and we have more nerve cells in our bowel than in our spine.5

The ENS is connected bidirectionally to the brain by parasympathetic and sympathetic pathways, forming the brain-gut axis. Sound complicated? It is. Neural control of the gut has four basic levels of integrative organization. Level one is the ENS—the “mind” of the gut. The second level of integrative organization is in the prevertebral sympathetic ganglia, and the third and fourth levels are within the central nervous system. In other words, the second and third levels provide input for the integration and action at the fourth level—or the higher brain centers.6 This rich neural complex governing gut function produces exactly the same chemicals that are found in the brain, including serotonin and acetylcholine. The multiplicity of neurotransmitters in the bowel suggests that the gut biochemical communication is rich and brainlike in its complexity.

Neurogastroenterology
This new area of medical specialization is called neurogastroenterology. It is a subspecialty of clinical gastroenterology and digestive science. It includes the investigative sciences dealing with functions, malfunctions, and malformations in the brain and spinal cord, and the sympathetic, parasympathetic, and enteric divisions of the autonomic innervation of the digestive tract.7

Neurogastroenterology is, however, a rediscovery of ideas and concepts dating from investigative work of the 19th century. Building on the early work of two British scientists, the existence of the ENS was discovered in Germany while the Civil War was raging in America. A German scientist by the name of Auerbach found that the bowel contains a complex network, or plexus, of nerve cells and fibers. This plexus is still called Auerbach’s plexus, though it is also known as the myenteric plexus. Additional neural gut networks were later identified, giving rise to the striking conclusion that the gut has an intrinsic nervous system with properties like those of the brain and spinal cord. Progress in neurogastroenterology brings us better understanding of the brain-gut axis and opens new therapeutic perspectives for the treatment of gastric health concerns.8

A Bad Bowel
Nutrition professionals have a keen appreciation for the fine-tuned process of digestion and absorption. When all is well, little attention is given to the gut. But when the system malfunctions, life can be miserable. Surveys indicate that more than 40% of patients who visit internists do so for GI problems. As noted earlier, the gut is the gatekeeper of the body, preventing harmful substances from infiltrating and making sure that nutrients are properly digested, absorbed, and delivered to cells and tissues in a form that can be used. Because the brain in the gut does its work largely unnoticed, it is often overlooked as a source of disease.

Of the patients presenting with GI problems, roughly 20% experience a condition known as functional bowel disease. The most common variants of this condition include nonulcer dyspepsia and irritable bowel syndrome (IBS). The diagnosis of functional bowel disease involves ruling out more serious conditions—carcinoma of the colon, Crohn’s disease, ulcerative colitis—and observing the presence of a set of general symptoms. These symptoms commonly include abdominal pain or cramping, a bloated feeling, gas, alternating bouts of constipation and diarrhea, and mucus in the stool (for IBS) and bloating, belching, gas, nausea, and a burning sensation or discomfort in the upper abdomen or lower chest (for nonulcer dyspepsia). Overall, no one specific set of diagnostic criteria exists, nor is there one clear causative agent.5

Nonulcer dyspepsia is a common, sometimes long-lasting (chronic) disorder of the upper GI system. It occurs for no apparent reason and isn’t necessarily related to a particular disease. Nonulcer dyspepsia does seem to be associated with certain lifestyle factors. Factors such as overeating or eating too quickly, drinking carbonated beverages, consuming spicy foods, and stress may increase the risk of the disorder.

Many of the early studies of IBS suggested that it was a disease predominantly affecting the white middle class. This is now known to be untrue. The prevalence of IBS seems independent of race, though there is some evidence that it may be affected by socioeconomic class and gender. You’re more likely to have IBS if you’re young and female. IBS typically begins around the age of 20. Overall, two to three times as many women as men have the condition.8 What is its cause? No one really knows. Some researchers note that hormonal changes may play a role given that more women than men are affected. Others believe IBS is caused by changes in the nerves that control sensation or muscle contractions in the bowel. While difficult to establish, it is thought that a malfunctioning ENS may be at least partly to blame for functional bowel disease.5 Once we have a clearer understanding of the ENS, it will open the way to new therapeutic approaches.

Finding Some Relief
Currently, treatment for both conditions focuses primarily on symptom relief. For people experiencing nonulcer dyspepsia, the treatment options include the following:

Medications
A number of medications are available for managing the signs and symptoms of nonulcer dyspepsia. They range from antacids that neutralize stomach acid to proton pump inhibitors that reduce acid by blocking the action of acid-secreting stomach cells to low-dose antidepressants that may help inhibit the activity of neurons that control the intestines to antibiotic treatment if Helicobacter pylori infection is detected.

Cognitive Behavior Therapy
Cognitive behavior therapy focuses on changing specific unwanted behaviors by bringing awareness to the behavior and then formulating specific steps to change. In the case of nonulcer dyspepsia, if the person tends to overeat or eat too quickly (often causing indigestion) behavior therapy would help change such habits.

Prevention
A healthier lifestyle can often prevent nonulcer dyspepsia. Lifestyle modifications that may help prevent signs and symptoms include dietary changes, stress management, and exercise.

Diet Tips
• Identify and avoid trigger foods. Some foods may serve as triggers for the signs and symptoms of nonulcer dyspepsia, such as fatty and spicy foods, carbonated beverages, caffeine, and alcohol.

• Practice conscious eating. Take time to savor food, chew thoroughly, and enjoy eating as a ritual.

• Don’t lie down right after a meal. Wait to lie down until at least two hours after eating.

• Maintain a healthy weight. Excess weight puts pressure on the abdomen, pushing up the stomach and causing acid to back up into the esophagus.

Stress
• Create calm. Turn off the television or computer during mealtimes. This may help relieve stress-related dyspepsia.

• Learn and practice relaxation techniques. There are a variety of ideas, including relaxed breathing, meditation, yoga, and progressive muscle relaxation.

Exercise
• Exercise tones the intestines and tissues and keeps digested food moving through the body. If not currently exercising, talk to your doctor first before beginning a new exercise routine.

• Get regular. Aim for at least 30 to 60 minutes of physical activity on most days of the week to achieve and maintain a healthy weight.

Controlling IBS
For individuals experiencing IBS, mild symptoms can usually be controlled by learning to manage stress and making changes in the diet and lifestyle. For moderate IBS, medications and over-the-counter remedies are frequently suggested to treat and control constipation and/or diarrhea. In some cases, drugs that affect certain activities of the nervous system (anticholinergics) to relieve painful bowel spasms may be prescribed.

Prevention, however, for IBS, as it is with nonulcer dyspepsia, is key. Finding ways to deal with stress can be extremely helpful in preventing or alleviating symptoms.

Stress reduction techniques that may be helpful include the following:

• Biofeedback. This technique helps reduce muscle tension and slow the heart rate with the feedback of a machine. A new computer program called Journey to the Wild Divine (www.edragonstore.com) offers biofeedback, music, and beautiful graphics as you learn to control your breathing while encouraging a hot air balloon to float through the sky. The goal is to help you enter a relaxed state so you can cope more easily with stress.

• Deep breathing. You become calmer when you breathe from your diaphragm, the muscle that separates your chest from your abdomen. When you inhale, allow the belly to expand with air; when you exhale, your belly naturally contracts. Deep breathing can also help relax your abdominal muscles, which may lead to more-normal bowel activity.

• Hypnosis. Hypnosis may help reduce abdominal pain and bloating. A trained professional teaches you how to enter a relaxed state and then guides you as you imagine your intestinal muscles becoming smooth and calm.

In many cases, simple changes in the diet and lifestyle can provide relief from IBS. The goal is to find long-term, supportive solutions. See the sidebar for more self-care ideas.

Directions for the Future
Progress in understanding the second brain in the gut has been rapid in recent years, though much remains to be discovered. Researchers are trying to unravel how the mind in the gut operates, and how precisely it orchestrates the dance of digestion. What we do know allows us to have greater appreciation and sympathy toward individuals who experience GI maladies with unknown causes. The focus of scientific attention on the second brain holds within it great potential for understanding how to treat and prevent functional bowel diseases and other GI disorders.

— Mary K. Sawyer-Morse, PhD, RD, is a professional speaker, author, and wellness expert. She is owner and education director of The Center for Success, a Texas-based company that provides keynotes, in-service training, and seminars to diverse industries.

References
1. Bhatia V, Tandon RK. Stress and the gastrointestinal tract. J Gastroenterol Hepatol. 2005;20(3):332-339.

2. Bresnick W. The effect of acute emotional stress on gastric acid secretion in normal subjects and duodenal ulcer patient. J Clin Gastro. 1993;17:117-122.

3. Greenwald DA. Diagnosis and management of nonulcer dyspepsia. Cortlandt Forum. March 2000:187-193.

4. Hill P. It is not what you eat, but how you eat it: Digestion, life-style, nutrition. Nutrition. 1991;7(6):385-395

5. Houghton LA, Calvert EL, Jackson NA, et al. Visceral sensation and emotion: a study using hypnosis. Gut. 2002;51(5):701-704.

6. Wood JD, Alpers DH, Andrews PLR. Fundamentals of neurogastroenterology. Gut. 1999;45(Suppl 2):II-II16.

7. Krammer HJ, Enck P, Tack J. Neurogastroenterology from the basics to the clinics. Gastroenterol. 1997;Suppl 2:1-68.

8. Mulak A, Bonaz B. Irritable bowel syndrome: A model of the brain-gut interactions. Med Sci Monitor. 2004;10(4):RA55-RA62.

More Self-Care Tips for Living with IBS
• Eat at regular times. Try to eat at about the same time each day to help regulate bowel function.

• Drink plenty of liquids. Try to drink plenty of fluids every day. Water is best. Alcohol and beverages that contain caffeine stimulate your intestines and can make diarrhea worse, and carbonated beverages produce gas.

• Exercise regularly. Exercise helps relieve depression and stress, stimulates normal contractions of your intestines, and can help you feel more confident and assured. Aim for 30 minutes of exercise most days.

• Experiment with fiber. With IBS, fiber can be a mixed blessing. Though it helps reduce constipation, it can make diarrhea, gas, and cramping worse. The best approach is to gradually increase the amount of fiber in the diet over a period of weeks. If using a fiber supplement (psyllium powder, Metamucil, or Citracel) be sure to introduce it gradually and drink plenty of water every day to minimize gas, bloating, and constipation.

• Be proactive. Learn as much about IBS as you can. Being informed about your condition can help you take better charge of it.

• Consider complementary approaches. Researchers at the National Institutes of Health have found that acupuncture can provide relief from chronic pain. Although study results on the effects of acupuncture on IBS symptoms have been mixed, some people use acupuncture to help relax muscle spasms and improve bowel function.

— MKSM

Subscribe to Today's Dietitian Magazine!