“Scientists call this little brain the enteric nervous system (ENS). And it’s not so little. The ENS is two thin layers of more than 100 million nerve cells lining your gastrointestinal tract from esophagus to rectum. Science is only beginning to understand the brain-gut axis and how it affects our brains, our moods, and our behavior. You may hear it referred to as the “brain-gut connection.” In the last decade, we’ve discovered that the gut has an outsize effect on the way our brains function.”