Bacteria, fungi, and other microbiota that populate the human gut number in the trillions, and scientific research is proving that these miniscule organisms make a big difference when it comes to physical and mental health.  A number of studies have shown a direct connection between the health of the human gut, and what is happening in the brain.  While many people with anxiety or depression have assumed that indigestion was a nasty side effect, it's possible that it is the other way around.  

The Other Nervous System

The central nervous system consists of the brain and spinal cord, but the human body houses another – the enteric nervous system – which regulates the function of the gastrointestinal tract.  Connecting the two nervous systems, the vagus nerve runs from the brain stem down the abdomen.  Although scientists originally thought the brain sent messages to the digestive system through the vagus nerve, studies show communication between the central and enteric nervous systems is a two-way street.

Serotonin is the feel-good neurotransmitter responsible for high spirits and a steady mood. While most people associate serotonin with the brain, 80 percent of the body's stores are actually manufactured in the intestines.  Not surprisingly, a serotonin imbalance can lead to occasional indigestion with symptoms like diarrhea, nausea, vomiting and constipation.

Related: Five Uncommon Causes of Constipation


A study conducted by a research team from UCLA found a connection between beneficial bacteria (or probiotics) ingested through food and brain function.  Eating yogurt containing probiotics induced effects in areas of the brain involved in emotion and sensory processing that did not occur in the brains of women who did not consume the yogurt.

"The knowledge that signals are sent from the intestine to the brain and that they can be modulated by a dietary change is likely to lead to an expansion of research aimed at finding new strategies to prevent or treat digestive, mental, and neurological disorders,” said Dr. Emeran Mayer, a professor of medicine, physiology, and psychiatry at UCLA's medical school and the study's lead author.

In future research, the UCLA team hopes to identify specific chemicals manufactured in the gut that activate the communication process from the enteric to the central nervous system.  They also plan to study whether improvement of indigestion symptoms like bloating, constipation, diarrhea, and abdominal pain relate to changes in the brain.

In addition to taking a high-dose daily probiotic and eating plain yogurt, people can boost the levels of beneficial bacteria in their guts by limiting sugar and processed foods and eating fermented foods like sauerkraut, tempeh, Kimchi, and miso.