Some researchers are now talking about your “second brain.” What are they referring to? Your Enteric Nervous System or ENS—otherwise known as your gastrointestinal system. What forms the basis for this designation? Neurons. Thinking cells. Your ENS contains a million-plus neurons. They look just like brain neurons, eat the same type of food (neurotrophins), and have at least 30 neurotransmitters in common. Most of the serotonin in your brain and body—perhaps as much as 90%—is found in your gut along with half of all the dopamine. Knowing this it should be no surprise that an upset stomach can trigger a headache and upset emotions can result in a GI upset (e.g., constipation, diarrhea). An excess release of serotonin can cause nausea and vomiting, and so on. There is a close connection between brain and body, specifically between your first and second brains. More tomorrow.