Small Intestine Bacterial Overgrowth (SIBO) & Key Factors For Successful Intervention

Small Intestine Bacterial Overgrowth (SIBO) is a chronic digestive system disorder that can cause significant problems such as constipation, diarrhea/loose stools, bloating, excessive gas, pain, cramping and increased food intolerance (1). SIBO is a form of Irritable Bowel Syndrome (IBS) that is caused by an overgrowth of normal colonic bacteria now found in the small intestine. These bacteria ferment various carbohydrates leading to hydrogen, hydrogen sulfide and methane gas which can damage the sensitive lining of the small intestine. However, SIBO is often much more than just a digestive disorder. Many individuals with SIBO can also suffer from chronic headaches, joint pain and inflammation, fatigue, depression, anxiety and sleep disorders (1). Chronic malabsorption is a serious complication of SIBO and can lead to rapid reductions in weight, nutrient depletion and immune system function. 

SIBO, in addition to having overgrowth of small bowel bacteria, also involves problems with stomach digestion, intestinal motility, bacterial toxin production, large intestine, liver bile acids production and bowel toxin elimination. For many individuals, SIBO can persist for years leading to a significant reduction in the quality of life. Many doctors have long recognized IBS as a chronic digestive system problem, but only recently has SIBO gained the attention of conventional medicine.

Increased awareness of SIBO is a positive thing within medicine. Typically, awareness leads to more research and treatment options. But, unfortunately, conventional medicines methods of treatment for SIBO are often short-sighted only involving use of antibiotics and promotility medications that are often not effective long-term. However, functional medicine practitioners have known for years that SIBO is a complex condition that requires a comprehensive treatment program for successful outcomes. 

SIBO is a condition that is known to afflict millions of people in the United States and around the world. According to the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) approximately 60 to 70 million people in the U.S. are affected by various digestive diseases, many of these are IBS related and SIBO is associated with IBS (2). 

Other problems that can either exist or cause SIBO are chronic infections such as fungal overgrowth (linked to candida and mold), clostridia bacteria (e.g. C. difficile), helicobacter pylori and parasitic infections. 

The key to successful SIBO treatment is it more than just overgrowth of bacteria in the small intestine. As mentioned before, SIBO involves stomach digestion, intestinal motility problems, liver, gallbladder and large intestine imbalances. Listed here are some important facts related to proper digestive function:

• All digestive functions need to occur in a coordinated manner. Enzymes released in the mouth and hydrochloric acid produced in the stomach triggers the release of bile from the liver and pancreatic enzymes into the small intestine. Without adequate enzymes and HCL (3), food is not properly broken down which allows for maldigested food substrate to be used for gas production in the small intestine. 
• The small intestine produces motilin (4), a hormone that increases gastrointestinal motility by stimulating the migrating motor complex (MMC). The MMC is myoelectrical system involved in intestinal movement of food and other digestive debris through the digestive system. It has a significant role over small intestine function. A compromised MMC, common in SIBO, increases the opportunity for small bowel bacteria accumulation. Bile acid production from the liver is another stimulant of MMC activity (5).  
• Large bowel function and elimination is also a critical component in SIBO. Constipation often leads to toxin accumulation in the digestive system. Those with diarrhea/loose stools often have bowel toxins too as this condition can be associated with excess hydrogen gas. All these factors can lead to dysfunction of the ileocecal valve (ICV) which is responsible for separating the large intestine from the small intestine. If the ICV does not function properly, bacteria from the colon can migrate into the small intestine. Keeping the bowels moving is essential to both treatment and prevention of SIBO.

1. Andrew C. Dukowicz, et. al., Small Intestinal Bacterial Overgrowth: A Comprehensive Review, Gastroenterol Hepatol, 2007 Feb; 3(2): 112–122.
2. Liu ZJ, et. al. Clinical features of irritable bowel syndrome with small intestinal bacterial overgrowth and a preliminary study of effectiveness of Rifaximin. 2016 Jun 28;96(24).
3. http://gastrodigestivesystem.com/stomach/low-stomach-acid-causes
4. Vantrappen G. Motilin and the interdigestive migrating motor complex in man. Dig Dis Sci. 1979 Jul;24(7):497-500.
5. Hellström PM. Role of bile in regulation of gut motility. J Intern Med.1995 Apr;237(4):395-402.