GERD, which stands for gastro-esophageal reflux disease, is caused by the reflux of acid from the stomach into the lower esophagus. This reflux then causes a variety of symptoms including burning pain in the chest, belching, chronic cough, and sore throat. While there are many possible underlying causes of GERD, one less talked about cause is SIBO (small intestinal bacterial overgrowth). As SIBO cases seem to be rising in the United States, I am seeing more and more patients in my practice who have SIBO-associated gastric reflux. While this is a newer area of study, we do have research to back up the association between GERD and SIBO. A recent study published in Surgical Endoscopy Journal in 2021 showed that 60% of patients referred for gastric reflux surgery tested positive for SIBO after breath testing (1).
SIBO occurs when we have an overgrowth of pathogenic bacteria in the small intestine. Typically, when we think of “good” and “bad” intestinal bacteria, we are talking about the large intestine. The small intestine, when healthy, houses very few bacteria. When there is bacterial overgrowth in this area, patients typically feel symptoms of early fullness when eating, uncomfortable gas and bloating, belching, and either constipation or diarrhea depending on what bugs are colonizing their intestinal tract.
So how could bugs in the small intestine possibly relate to acid in the esophagus? The answer mostly comes down to pressure. Many cases of GERD are not caused by high acid levels, but rather a “leaky” lower esophageal sphincter (the barrier between the stomach and the small intestine). A healthy sphincter opens up when food is traveling down the esophagus to allow it into the stomach. The sphincter then closes securely, preventing backflow of any acid after we are finished eating.
Patients with SIBO have high levels of hydrogen and/or methane gas buildup in the abdomen. This pressure then causes transient lower esophageal sphincter relaxations to help vent this gas out of the stomach. When the sphincter relaxes, we have a backflow of acid into the esophagus along with the gas.
The association between SIBO and GERD may explain why certain GERD patients feel much worse when taking antacid medications. It is already known that antacids increase the prevalence of SIBO due to acid being a first-line protection from bacterial infections entering through the mouth. Additionally, patients who developed reflux for other reasons besides SIBO are eventually at high risk of developing it due to acid suppression. Therefore, SIBO should always be considered when treating patients for any kind of gastroesophageal reflux disease.
Dr. Katie Nuckolls is a naturopathic physician and owner of Thrive GI: Natural Digestive Medicine in Vancouver, Washington. She currently sees patients that live in Washington, Oregon, and Arizona using telemedicine. For more information, visit our contact page or schedule a free 15-minute consultation online.