Cedars-Sinai Blog
Causes and Treatments for Irritable Bowel Syndrome
Irritable bowel syndrome (IBS) is a common condition, estimated to affect 10%-15% of adults. Women are almost twice as likely to have it as men.
IBS causes gut bloating and pain, and those affected suffer from constipation, diarrhea or a combination of the two.
IBS is not the same as inflammatory bowel disease or other gut-based diseases. Instead, IBS has become a kind of catch-all for gut-related pain that does not fit the profile for these other conditions.
"We started studying the microbiome even before that term came about. We found that IBS patients had an overgrowth of bacteria in their small intestine."
What Causes IBS?
For many years IBS was thought to be caused by stress or anxiety—before a Cedars-Sinai expert proved otherwise for the majority of cases.
Most of us have experienced a “nervous stomach.” And because women are more likely to have IBS, gender stereotypes led many in the mostly male medical profession to discount the pain it created, putting it down to hypochondria and hysteria.
But while anxiety can make IBS symptoms worse, gastroenterologist Mark Pimentel, MD, says research at Cedars-Sinai has shown that about 60% of IBS cases are caused by certain bacteria in the gut resulting from food poisoning.
Mark Pimentel, MD
"In 1999, we started studying the microbiome even before that term came about," said Pimentel. "We found that IBS patients had an overgrowth of bacteria in their small intestine."
The activity of these bacteria breaking down food creates gas, hence the bloating experienced with IBS.
"We found three different types of bacteria," Pimentel explained. "One creates hydrogen, which is associated with diarrhea. Methane is associated with constipation, and hydrogen sulfide causes more extreme cases of diarrhea."
Pimentel and the Cedars-Sinai researchers developed a breath test for these gases that can identify the three different kinds of IBS.
How Can IBS Be Treated?
Pimentel says that because IBS has been identified as a syndrome defined by symptoms—rather than a disease defined by a root cause—treatments historically have focused on alleviating symptoms: laxatives for constipation, antidiarrheals to slow the gut.
"But when you treat the symptoms, the underlying disease is still there," said Pimentel.
Cedars-Sinai researchers found the bacteria causing IBS could be treated with antibiotics.
"With this treatment, patients get better and they stay better," said Pimentel. "Two weeks of the antibiotic and you’re good for six months."
Around the six-month mark, bacterial growth can start to recur. The race is on, Pimentel says, to develop more durable treatments.
Diet is also an important component. Pimentel recommends a low-fermentation diet, which restricts foods that are harder to digest such as fiber or non-digestible sugars—stevia and sucralose, for example.
"That won’t cure the IBS," said Pimentel. "But if you get rid of the bacteria, then diet can help prevent recurrence."
Using the Gut-Brain Connection to Treat IBS
The ways in which the gut microbiome may affect the brain has become a hot topic for research. For example, mood disorders, such as depression, are linked to serotonin, a chemical produced mostly in the gut that helps nerve cells pass messages throughout the body. And studies are looking into whether Parkinson’s disease, a degenerative brain disease, also has its root cause in the gut microbiome.
The same nervous system that makes it possible for the gut to affect the brain also allows for effects to travel in the opposite direction.
"The brain doesn't just have to sit there helplessly receiving pain signals from the gut," said gastroentorologist Brennan Spiegel, MD, director of Health Services Research at Cedars-Sinai. “It can fight back by sending inhibitory signals down the spinal cord."
Cognitive behavioral therapy is a type of mental health therapy used to treat many conditions. Spiegel says this type of therapy can help treat the pain and anxiety caused by IBS. He says the physical responses to anxiety are like a software program that runs when a person feels fear.
"The heart rate will speed up, the gut will slow down, sweat will form in the skin and the eyes will dilate," he said. "All these things are designed to keep us alive when a lion is coming at us and we have to run."
Most of us aren’t facing lions in our modern-day lives, but Spiegel says the fear program still launches much too often in many IBS patients because they’re hypersensitive to their symptoms. Their anxiety is heightened because they know that a sudden, unexpected and embarrassing onset of diarrhea can happen anywhere and anytime. With the use of relaxation strategies, exposure therapy and other techniques, cognitive behavioral therapy can help short-circuit the software program, reducing pain and anxiety when IBS symptoms appear.
"With eight to twelve weeks of daily practice, 60%-80% of people with IBS will see their symptoms improve," he said.
