A healthy colon is like a beating heart. In addition to nerves and hormones regulating movement in your colon, electrical activity in its muscles keeps the contents of your colon moving at a healthy pace, much the same way your body controls the beating of your heart.But when something goes wrong, it can lead to irritable bowel syndrome (IBS), meaning that the movement in your colon speeds up (causing diarrhea) or slows down (causing constipation). When you have diarrhea, your colon doesn’t absorb enough water before the contents move out during a bowel movement. And when you have constipation, your colon absorbs too much water. In either case, you may also feel bloating, abdominal pain, and cramping.
What Causes Irritable Bowel Syndrome?
Researchers haven’t yet discovered why some people experience IBS, but there are a few theories about what causes it:Abnormal serotonin levels. One dominant theory is that IBS is related to serotonin in the gut, says Steven Field, MD, a gastroenterologist and clinical assistant professor of medicine at New York University School of Medicine in New York City. You may have heard of serotonin as a chemical in your brain that helps to regulate your mood. But, actually, that work is only a fraction of its job. While a percentage of your body’s serotonin is found in your brain, it is also found in the walls of your colon. There, it may regulate bowel contractions and movements and secrete fluid, Dr. Fields says.
Researchers have found that if you have an abnormal amount of serotonin in your gut or if the serotonin in your gut isn’t functioning the way it should, it can lead to IBS symptoms, Fields says. It could be why some people see an improvement in their IBS symptoms when they take antidepressants, many of which work by adjusting serotonin levels.Analyses of studies that have tested the effects of antidepressants on IBS symptoms have found that the drugs improve overall symptoms, including abdominal pain and diarrhea. Researchers have found that one in three people treated with a tricyclic antidepressant (a class of antidepressants that affects the absorption of serotonin) experiences a significant improvement in symptoms.
Bacterial overgrowth. Some research has found that people with IBS have an overgrowth of bacteria in their small intestine, which may be a cause of IBS symptoms.It could explain why studies have found that taking an antibiotic can give IBS sufferers relief from their symptoms.In one recent study of 87 adults with IBS, researchers gave the patients either an oral antibiotic or a placebo three times a day for 10 days. After treatment, they were asked about the severity of their symptoms, including diarrhea, constipation, abdominal pain, and bloating. Those who had taken the antibiotic reported a bigger overall improvement in IBS symptoms compared to those who took a placebo. In addition, the improvement lasted 10 weeks, even after they stopped taking the antibiotic.
Bacterial infection. Some people who have had a bacterial infection, or gastroenteritis, in their gastrointestinal tract go on to develop IBS.Other theories implicate stress, diet, and inflammation of the intestines. While antidepressants and antibiotics may help ease some of the symptoms, there are other ways to get relief too — through other medications, reducing your stress levels, and by changing your diet. If you have symptoms of IBS, it’s always important to see your doctor.