What Your Gut Says About Your Health

Your Stomach's Role in Your Health

Going with your gut feelings is a good practice. Too bad I don't always like what mine are saying. When I'm stressed, nervous, or feeling down, my stomach pings and my insides churn. It's as if there's an E-ZPass lane connecting my brain and bowels, its sign flashing "Go, go, go." And I suddenly have to. Badly.

See, when it comes to mood, it's not all in your head -- it's in your gut, too. "The brain influences the digestive tract and vice versa," says Rebekah Gross, MD, a clinical gastroenterologist at NYU Langone Medical Center. In fact, new research has found that our esophagus, stomach, small intestine, and colon have a big say in how our minds and bodies function and how happy we feel. "The gut is a critical group of organs that we need to start paying more attention to," says Steven Lamm, MD, the author of No Guts, No Glory. "Doing so may be the secret to improving our overall wellness."

If it seems as if your stomach sometimes has a mind of its own, that's because it does. The gut's lining houses an independent network of hundreds of millions of neurons -- more than the spinal cord has -- called the enteric nervous system. It's so complex and influential that scientists refer to it as "the second brain." In addition to being in charge of the digestive process, your gut lining is the core of your body's immune system (who knew?) and defends you against such foreign invaders as viruses and bacteria. "It's a very important barrier, as important as the skin," says Michael Gershon, MD, the author of The Second Brain and the pioneering gastroenterologist who coined the term.

Cells in the gut lining also produce 95 percent of the serotonin in our bodies. (The rest occurs in the brain, where the hormone regulates happiness and mood.) In the gut, serotonin has a range of functions, including stimulating nerve-cell growth and alerting the immune system to germs.

Thanks to serotonin, the gut and the brain are in constant contact with each other. Chemical messages race back and forth between the brain's central nervous system and the gut's enteric nervous system. When we're stressed, scared, or nervous, our brain notifies our gut, and our stomach starts to churn in response. When our digestive system is upset, our gut alerts our brain that there's a problem even before we begin to feel the symptoms. Scientists suspect that our moods are negatively affected as a result. "The gut is sending messages that can make the brain anxious," Dr. Gershon explains. "You're in good mental shape only if your gut lets you be."

Other key -- and minuscule­ -- players in all this brain-and-bowels communication are the microbes that line the walls of the gut, says gastroenterologist Gianrico Farrugia, MD, the director of the Mayo Clinic Center for Individualized Medicine. There are hundreds of types of bacteria in the gut; some of them do helpful things like break down carbohydrates in the intestine and produce infection-fighting antibodies and vitamins, while other, destructive bacteria secrete toxins and promote disease.

In a healthy gut, the good bacteria far outnumber the bad. But what's going on in your head can affect the balance. "Emotional issues can help influence what lives in your GI tract," says William Chey, MD, a professor of internal medicine at the University of Michigan Medical School. Being under a great deal of stress or feeling depressed or anxious could change the way your bowels contract and how your immune system functions, which in turn can change the type of bacteria in the small intestine and colon, he explains. Symptoms can include cramping, bloating, diarrhea, or constipation.

For instance, irritable bowel syndrome (IBS), a disorder that causes abdominal pain, diarrhea, and constipation, often accompanied by gas and bloating and sometimes by anxiety and depression, can be related to an overabundance of bad bacteria in the small intestine. Women are particularly susceptible to this, especially if they experienced sexual abuse or psychological trauma as a child. It's not known if the stress causes the symptoms or vice versa. "But the two definitely feed off each other, and IBS flares in stressful circumstances," Dr. Gross says.