Experiencing weird stomach issues like nausea, bloating, and diarrhea can send you down the rabbit hole of Google searches. After all, these symptoms can be a sign of plenty of different GI problems, one of which is something called small intestinal bacterial overgrowth, or SIBO.
Have next to zero idea what SIBO is about? Fair. While it doesn’t get as much attention as fellow GI conditions such as irritable bowel syndrome (IBS) or acid reflux, SIBO is a thing that plenty of people have had to deal with.
Just know this upfront: There are a lot of questions surrounding SIBO, and it can easily be confused with other gastrointestinal diseases. Even if you are diagnosed with SIBO, it can be tricky to find out why you have it in the first place. “We don’t always know what causes it,” says LeaAnn Chen, MD, assistant professor of medicine at Rutgers Robert Wood Johnson Medical School and director of Inflammatory Bowel Disease Translational Research for the Division of Gastroenterology and Hepatology. There is a test for SIBO, though, along with treatments.
Curious to know more? Pull up a seat.
What exactly is SIBO—and what causes it?
SIBO happens when there’s an unusual increase in the overall population of bacteria in your small intestine, especially in types of bacteria that aren’t normally found in that area of your GI tract, according to the Mayo Clinic.
SIBO usually happens when someone has surgery or a disease that slows down the movement of food and waste in the GI tract, explains Ashkan Farhadi, MD, a gastroenterologist at MemorialCare Orange Coast Medical Center in Fountain Valley, California. This can allow certain bacteria that aren't welcome in high numbers in the small intestine to thrive there and lead to uncomfortable symptoms.
It’s not entirely clear why some people develop SIBO and others don’t, but there are a few things that can raise your risk of the condition. Those include a change in your gut motility (how fast stuff moves through the area) from medications like narcotics, diabetes, and decreased gut acid from the use of acid-reducing medications like proton pump inhibitors, says Richa Shukla, MD, assistant professor of medicine, gastroenterology at the Baylor College of Medicine. SIBO can also be a complication of having gastrointestinal surgery, Dr. Chen adds.
SIBO has a lot of overlapping symptoms with IBS, and some people with irritable bowel syndrome also have SIBO. One study estimates that anywhere from 4 to 78 percent of IBS patients have SIBO, too. “IBS is challenging in that there really is no diagnostic test for it,” Dr. Chen says. “That makes it very easy to confuse IBS with SIBO, and there is some overlap.”
What are the symptoms of SIBO to look out for?
The symptoms of SIBO can be a little vague and easily confused with other GI issues. Here’s a breakdown, according to the Mayo Clinic:
Having no or less of an appetite
Feeling super full after you eat
Unexplained weight loss
Is there a test I can take to tell if I have SIBO?
If your doctor suspects you might have SIBO, they’ll give you a test for it. There are two options:
A breath test. This test measures the amount of hydrogen or methane that you breathe out after you drink a mixture of glucose (a.k.a. sugar) and water. If you have a rapid increase in exhaled hydrogen or methane, it can suggest that you have a bacterial overgrowth in your small intestine. “The breath test is often used to distinguish between SIBO and IBS,” Dr. Chen says.
A culture from your small intestine. This test is more invasive but it’s considered the best option. To do it, doctors will pass a long, flexible tube down your throat and through your upper digestive tract to your small intestine. There, they’ll take a sample of your intestinal fluid and test it in a lab for bacterial overgrowth.
How is SIBO treated?
If you do, in fact, have SIBO, you’ll be treated with antibiotics, usually rifaximin, Dr. Shukla says. Unfortunately, that doesn’t always do the trick. “About 40 percent of patients may have persistent symptoms after the first course of antibiotics and will require a second course,” Dr. Shukla says.
If you’re still struggling with symptoms after that, your doctor will probably ask you to change up your medications and diet to see if that makes a difference, Dr. Farhadi says.
What foods should I avoid if I have SIBO?
Dr. Farhadi warns against eating “foods that are really sugary.” So, pastries, desserts, and candy should be pushed to the side. Ditto for foods packed with carbs (which convert to sugar in your body) and alcohol. “They encourage SIBO. The bacteria feed off of [sugar],” Dr. Farhadi says, before warning, “watch what you eat.” (A gastroenterologist and/or nutritionist with experience helping people with SIBO can help guide you as you make dietary changes.)
You may have heard that probiotics are actually bad when you have SIBO, but Dr. Farhadi says that’s not totally accurate. “Probiotics are your friend,” he says. “They can replace the bad bacteria with good bacteria.” People with SIBO who took probiotics had a “significantly higher” rate of recovering from the condition than those who didn’t take probiotics, per one meta-analysis published in the Journal of Clinical Gastroenterology.
The bottom line: If you think you might be struggling with SIBO and are dealing with several of the symptoms, it's worth talking to your doctor to find out for sure so you can get on a course of treatment.
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