Raise your hand if you’ve ever experienced uncomfortable bloating in your belly after eating a meal. I raised my hand, and you probably did, too. It is common for all of us to have burping, passing gas, and abdominal discomfort if we eat foods that–for us, anyway–are hard to digest.
But what if you have bloating, abdominal pain, increased gas, frequent burping with every meal? Or even with small snacks, or all the time? Chances are you may have SIBO, as these are classic SIBO symptoms.
What is SIBO?
SIBO, small intestinal bacterial overgrowth, is defined as an increase in the number of bacteria, and/or changes in the types of bacteria present in the small bowel. Usually, SIBO is not caused by a single type of bacteria, but rather by overgrowth of many types of bacteria that should normally be found in the colon, including E. Coli, Klebsiella, Aeromonas, Firmicutes, and Proteobacteria.
There are a couple of common ways bacteria can end up in the small intestine, which is a segment of the digestive system that is normally low in bacteria. One way is through low stomach acid. One of the functions of stomach acid is to destroy the bacteria we eat in our food every day. When stomach acid is low, bacteria survive and pass from the stomach to the small intestines, where they may proliferate and overgrow.
Another way bacteria make their way into the small intestine is through the backward motion of bacteria from the colon into the small intestine. There is a valve between the colon and small intestine, called the ileocecal valve, that normally prevents this. But in some individuals, the valve doesn’t work well, or the motion of the colon is such that the valve can be overcome, allowing bacteria to migrate backwards into the small intestine.
In addition to the protective measures of adequate stomach acid and a functioning ileocecal valve, the small intestine has several other ways it protects itself from bacterial overgrowth. The small intestine has rhythmic waves that occur regularly to keep the contents of the small intestine moving along, as well as to regularly mix them to enhance digestion. In people with chronic constipation, these waves may not occur as often. Additionally, many medications slow the waves, allowing the small intestinal contents to stagnate. All of this is a set-up for SIBO.
What is the function of the small intestine?
The small intestine plays a key role in digesting and absorbing nutrients. Millions of finger-like projections, called villi, create an impressive amount of absorptive surface area, and carbohydrates, fats, proteins, vitamins, and minerals all make their way into our bodies through the small intestinal wall. The small intestine also contains an abundant amount of immune tissue (as does the colon), and a small amount of normal bacteria that assist with digestion.
SIBO has been shown to negatively affect both the structure and function of the small bowel. It may significantly interfere with digestion of food and absorption of nutrients, primarily by damaging the cells lining the small bowel. Because of this damage, malnutrition and weight loss can occur as severe SIBO symptoms.
How is IBS related to SIBO?
It is estimated that up to 80% of people diagnosed with IBS (irritable bowel syndrome) may actually have SIBO as an underlying cause of their loose stools (or constipation), abdominal pain, and belly bloating. Chronic SIBO can create a gut environment that is unsupportive of a healthy microbiome, which can lead to leaky gut–larger proteins making their way across an otherwise impenetrable gut wall, leading to immune activation, inflammation, and possible food sensitivities. In functional medicine, it is important for us to look at all sources of gut dysfunction when patients have symptoms in order to have the greatest impact on resolving them.
SIBO symptoms can vary with the type of SIBO
It is important to note that there are actually three different types of SIBO, and the symptoms of each can be somewhat different. We’ve spent the majority of this article discussing SIBO, but in fact two other overgrowth syndromes involving the small intestine exist: intestinal methanogen overgrowth (IMO) and hydrogen sulfide excess.
All three of these forms of SIBO can cause uncomfortable bloating. In general SIBO (both hydrogen and hydrogen sulfide forms) cause loose stools, while IMO is generally associated with constipation and overall slow motility of the gut.
The bacteria that cause the different types of SIBO are also different. While the traditional form of SIBO is typically caused by the bacteria listed at the beginning of this article, IMO is generally associated with Methanobrevibacter smithii, which is a member of the archaea family (which technically aren’t bacteria), while hydrogen sulfide SIBO is associated with Desulfovibrio species of bacteria. All of these organisms are considered to be a normal part of the microbiome, but shouldn’t be present in large amounts in the small intestines.
How is SIBO diagnosed?
SIBO used to be diagnosed via biopsy from an endoscopy (scope inserted through the mouth and down into the upper digestive tract). Thankfully, this uncomfortable and costly procedure can be avoided with a newer approach that can be done at home. SIBO breath testing involves consuming a specific quantity of lactulose (a sugar that stimulates digestion) and measuring both hydrogen and methane levels in samples obtained from breathing into a test tube every 30 minutes. These samples are then analyzed and plotted out over time. When levels of hydrogen or methane (or with some testing kits, hydrogen sulfide) rise above a certain threshold at certain timing intervals, the diagnosis can be made.
How are SIBO symptoms treated?
The most important step in treating SIBO is to eradicate the bacterial overgrowth. Several protocols involving both prescription medications as well as botanicals with antibacterial properties have been successfully used to treat all three forms of SIBO. Typically, an antibiotic called Xifaxan (generic rifaximin) is taken three times a day for 14 days. This antibiotic does not get absorbed into the body, acting directly in the gut to remove bacterial overgrowth. Sometimes, metronidazole or neomycin (also antibiotics) are used in place of Xifaxan or, in some cases, in addition to Xifaxan.
Controversy exists around using dietary changes in the treatment of SIBO. These diets include low FODMAP, elemental diets, and low-fiber diets. Work done by Dr. Mark Pimintel, gastroenterologist at Cedars Sinai Hospital in Los Angeles, would suggest that these diets don’t add much during treatment of SIBO, but using them after treatment sometimes helps SIBO sufferers prolong the positive outcome of antibiotics. In general, we don’t want people using restrictive diets any longer than they have to. Working with your functional medicine physician or functional nutritionist can help create an actionable and personalized nutrition plan during and after SIBO treatment.
The bottom line
SIBO is common in people with GI symptoms, and it is treatable. Working with a functional medicine physician, you’ll be heard and validated. With the proper testing, you can get an accurate diagnosis and be on your way to finally feeling better quickly.