Healthy Digestive Function
A healthy digestive system has a number of functions:
1. To break down food into small nutritional components that provide the vitamins, minerals, proteins, water and energy needed to maintain health.
2. To collect toxins, dead cells and other debris, and eliminate them from the body.
3. To act as a site for front-line immune defense.
During digestion, digestive enzymes, acids and other chemicals mix with food in the mouth, stomach and intestines to break down the food and extract nutrients. The intestinal wall acts as a filter, keeping toxins and debris inside and moving toward elimination while allowing the smaller nutrients to pass freely through the wall to enter the bloodstream. Once inside the blood, the nutrients are carried to all the tissues of the body that need them.
Because digestive chemicals are very caustic and the specialized function of the digestive wall is so important, the linings of this wall are continually replenished to maintain its integrity. In fact, this is one of the areas of fastest cell turnover in the body. The degree of integrity of this wall has an impact on overall health, as well as the health of the digestive system because it affects the availability of energy and nutrients to cells throughout the body. Just as important are the quantity of digestive chemicals secreted, the length of time it takes the contents of digestion to move through the tract, the balance of intestinal bacteria, and the vigor of intestinal immune function. Stress modifies all of these aspects of your digestive system through the combined actions of your nervous system and adrenal hormones. To understand how this happens, it helps to first understand a little about how the nervous system affects the digestive system and what changes occur during the stress response.
Digestion and the Nervous System
Digestive system function is regulated by the autonomic nervous system (ANS). The purpose of the ANS is to control a vast array of life-sustaining activities in the body without requiring conscious thought. Imagine how exhausting it would be to have to remember to instruct your stomach to empty or to remind your mouth to secrete saliva. The ANS is subdivided into three main parts: 1. the enteric, 2. the sympathetic and 3. the parasympathetic nervous systems.
1. The enteric branch manages every aspect of digestion. It is sometimes referred to as the “second brain” or “gut brain” because in addition to innervating the smooth muscles, glands and organs of the digestive system, it produces neurotransmitters (brain messenger chemicals) in the gut that can influence cognition and mood as well as digestive function. It works independently and also interacts with the rest of the ANS to regulate the digestive system and modulate digestive function during stress.
2. The sympathetic branch responds to stress and mobilizes the body for a physical reaction, generally inhibiting digestion so that more resources are available to the brain, heart and muscles.
3. The parasympathetic branch is responsible for maintenance, repair, restoration, relaxation and digestion. The phrase “rest and digest” is sometimes used to describe what it does. Under the control of the parasympathetic nervous system, the following processes of digestion are supported:
• Food travels through the tract at the optimal pace for nutrients to be absorbed
• Muscular contractions in the intestines are smooth and regular
• Sphincters are opened to allow normal passage of food through the gut
• A special type of mucus is continually secreted over the inner walls of the stomach and intestines to protect them against caustic digestive chemicals
• The lining of the tract is maintained and repaired regularly
• Blood flows through the digestive organs to receive nutrients from food and to bring oxygen from the lungs
• Beneficial bacteria grow, supported by a balanced intestinal environment
• The immune cells in the digestive tract protect the body and the tissues of the digestive system against infection