Our Second Brain: The Stomach By Psychology Today Staff, published on May 01, 1999 Ever get a gut feeling about someone, or I anxious butterflies in your stomach? That's because you have a second brain in your bowel, according to Michael Gershon M.D., author of The Second Brain (HarperCollins, 1999), and a neurobiologist at New York`s Columbia-Presbyterian Medical Centre. Gershon recently explained to PT how an independent network of over 100 billion neurons in the gut not only signals our bodies to stress, but causes illness. Q Why do we need a second brain? A Most importantly, to control digestion. It also works with the immune system to protect us from hostile bacteria. Q Does it use neurotransmitters? A Actually, 95% of all serotonin in the body is in the gut, where it triggers digestion. Nerve cells in the gut also use serotonin to signal back to the brain. This information can train us not to eat certain foods by communicating pain, gas and other terrible feelings.
Q Does the brain in our heads influence the "second brain"? A Yes. Butterflies in the stomach arise when the brain sends a message of anxiety to the gut, which sends messages back to the brain that it's unhappy. But the gut can also work in isolation. Q How does this brain influence irritable bowel syndrome (lBS), which many believe is a psychological problem? A Irritable bowel syndrome, whose symptoms include abdominal pain accompanied by loose stool, affects 20% of Americans. But doctors often dismiss its severity, attributing IBS to psychoneurosis because they don't know exactly what it is. I propose that the second brain is the cause. Some antidepressant, when used in doses too low to treat depression, are effective immediately in IBS patients. Prozac takes weeks to kick in. This suggests that the drugs work not only on the brains of people with IBS, but on the bowel.