What is a gut feeling?
No doubt you have watched a scary movie, and shortly before one of the characters enters a critical stage of the film, you hear: “I have a bad feeling about this.” This statement is usually followed by a sequence that reaffirms these gut-wrenching emotions and the character meets their nemesis. Can our gut actually anticipate foreboding actions though? The science says yes.
One of the best examples of our gut getting involved in emotions occurs during the ‘fight or flight’ response. This well-known phenomenon is a group of physiological reactions to a perceived threat. During the response, heart and lung activity increases, digestion slows to a halt and blood vessels are constricted throughout the body. At the same time blood is flowing to the lungs and muscles, less is flowing to the stomach and this can cause nausea. This accounts for that familiar queasy feeling or the butterflies in the stomach, during stressful situations. These actions are controlled by the body’s sympathetic nervous system, which is part of the autonomic nervous system that regulates the function of our internal organs.
Fortunately, the stress response is not always engaged, but our digestive system remains capable of reacting to emotions to a degree that is just now being understood. Besides being comprised of the esophagus, stomach, and intestines, our digestive system also contains a mass of neural tissue with over 100 million neurons, which is more than is found in our spinal column. These neural circuits comprise the enteric nervous system which controls local blood flow as well as digestive activity. Emerging views of this system, also referred to as a “second brain” by some scientists, show that it does more than just handle digestion.
The second brain operates digestion without the brain even getting involved. Between managing behavior and controlling thoughts, the brain has enough on its mind already. The brain in the gut uses its power to manage the various facets of digestion that include breaking down food and absorbing nutrients. However, given the amount of neural capacity available in the gut, scientists know there is more to learn about this system.
The enteric nervous system uses about the same number of neurotransmitters as the brain and given some of these commonalities it is not surprising to learn why many treatments for mental health issues, like depression, also unintentionally impact the digestive system. For example, most of the serotonin in our body is produced in the gut, so when a person takes selective serotonin reuptake inhibitors (SSRIs) for treatment of depression they commonly experience dry mouth and nausea as the medications are also impacting the same neurotransmitters involved in digestion, like those that help secrete saliva.
Determining the intricacies within the second brain will provide solutions to many common health problems. For example, Irritable bowel syndrome has been connected to elevated serotonin levels in the gut which can overwhelm the various receptors and create a cascade of digestive issues such as diarrhea or constipation. Research is also examining how the second brain is impacting our immune response since 70 percent of our immune response is directed towards to gut. A healthy gut therefore builds a healthy immune response.
In the meantime, it is still helpful to know what to do when those gut feelings, or butterflies, do occur. Remember to take deep breaths, which gets oxygen to the brain, and to think positive. If the butterflies keep coming on, you may need to just avoid those trigger situations.
Think of how beneficial that would be for those movie characters.
-Jon Vredenburg, MBA, RD, CDCES, LD/N
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