Did you know you have two brains? Our gastrointestinal tract has been dubbed our "second brain" because it contains 500 million nerve cells! Find out how to keep our amazing gut healthy. Modern gastroenterology suggests our “gut instinct” stems from the 500 million neurons contained in the gastrointestinal tract, in the network of nerves contained in the walls of everything from our esophagus to our stomach and intestines. That network—the enteric nervous system (ENS)—is what’s known as the “second brain.” And for good reason. The ENS is the body’s second-largest concentration of nerves behind only the brain (and ahead of the spinal column). In fact, there are 30 to 40 percent as many neurotransmitters identified in the gastrointestinal tract as there are in the brain. The Body’s Prime Source of Serotonin The ENS controls digestion, including everything from the biomechanics of the stomach and intestines to the alkalinity that allows digestive enzymes to