Gut bacteria manufacture about 95% of the body’s supply of serotonin. Serotonin is a neurotransmitter or chemical messenger released by a nerve cell. Serotonin is essential in the treatment of depression and anxiety. It also plays a role in the normal operations of most of our brain functions, including regulation of mood, appetite, sexual functioning, memory, and sleep. Deficits of serotonin lead to increased irritability, anxiety, depression, and anger.
In some promising studies with mice, researchers found that anxious mice given water laced with probiotics (helpful bacteria) were less likely to give up during a physical challenge and produced less stress hormone, corticosterone (showing a reduction of symptoms of depression and anxiety). A study with human subjects showed a significant decrease in anxiety and depression after only a 30-day course of probiotics.
A growing body of research demonstrates that a healthy mix of bacteria in the gut can improve our physical and mental health. To better understand how this works, let us start with a basic understanding of digestion.
Digestion begins in the mouth. As you chew that crispy McIntosh apple, saliva starts to break down the nutrients. The action of chewing sends a message to your stomach to release digestive enzymes to break down the nutrients further. Muscles and mucosa continue breaking down the foods we eat as they move through our digestive tract (mouth, esophagus, stomach, small and large intestine, rectum, and anus).
When we race through the day, multitasking while shoving food into our mouths, we add stress to the work of digestion. Stress can cause the esophagus to spasm. It can also cause indigestion. Indigestion increases the environment for the growth of unhealthy bacteria in the gut. Harmful bacteria trigger a discordant cascade of unpleasant symptoms.
Over time, chronic, unmanaged stress can lead to inflammatory responses and disease. You can decrease and even eliminate these toxic effects with a daily stress management practice, like the practices offered in this book. When you learn to generate a feeling of internal peace and harmony, your body responds and soothes itself.